Download Nitrene Transfer Reactions Mediated by Transition

Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes
A dissertation presented to
the faculty of
the College of Arts and Sciences of Ohio University
In partial fulfillment
of the requirements for the degree
Doctor of Philosophy
Shengwen Liang
August 2012
© 2012 Shengwen Liang. All Rights Reserved.
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This dissertation titled
Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes
by
SHENGWEN LIANG
has been approved for
the Department of Chemistry and Biochemistry
and the College of Arts and Sciences by
Michael P. Jensen
Associate Professor of Chemistry
Howard Dewald
Interim Dean, College of Arts and Sciences
3
ABSTRACT
LIANG, SHENGWEN, Ph.D., August 2012, Chemistry
Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes
Director of Dissertation: Michael P. Jensen
Transition metal catalyzed C=C bond aziridination and C-H bond amination
reactions are powerful synthetic methods for forming C-N bonds directly from
unfunctionalized hydrocarbons, and have enormous synthetic potential in chemical
processes leading to natural products, pharmaceuticals and materials. Catalytic C-H bond
amination also offers a way to achieve functionalization with clean and environmentally
sustainable atom efficiency.
This work will focus on olefin aziridinations and C-H bond aminations catalyzed
by transition metal complexes. We employed N3-tripod scorpionate ligands to support
different transition metal centers. Therefore, complexes [(L)M(NCCH3)3](BF4)n (L =
tris{3,5-dimethylpyrazol-1-yl}methane, TpmMe,Me, M = Mn, Fe, Co, Ni, n = 2; L = tris{3phenylpyrazol-1-yl}methane, TpmPh, M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5dimethylpyrazol-1-yl}borate, TpMe,Me, M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5methylpyrazol-1-yl}borate, TpPh,Me, M = Mn, Co, Fe, Ni, n = 1) were prepared and
characterized. These complexes were utilized as metal catalysts for nitrene transfer from
phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in
olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide
range of organic products was obtained and fully characterized, and reaction mechanisms
were probed with Hammett and kinetic isotope effects. Meanwhile, a masked Lewis acid
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[Fe(NCMe)6](BF4)2 was found to catalyze [2+1+2] and [3+2] cycloaddition reactions,
leading to the formation of various five-membered nitrogen-containing compounds.
Approved: _____________________________________________________________
Michael P. Jensen
Associate Professor of Chemistry
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To My Parents Xiuzhen Qiu and Guoping Liang
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ACKNOWLEDGMENTS
This dissertation, and all of my research work at Ohio University, would not have
been possible without the time and support of quite a few people. I need to begin with
thanking my advisor Prof. Michael P. Jensen for giving me the opportunity to work in his
laboratory on such an interesting research project. He has been a wonderful mentor
offering me patience and guidance throughout the past five years. It seems to me that I
gain valuable lessons not only on chemistry but also on scientific method, logic, and
interpersonal relationships that would be valuable for my future career.
In addition, I would like to thank the members of my committee, Prof. Jeffrey J.
Rack, Prof. Hao Chen and Prof. R. Guy Riefler. Prof. Rack in particular has been a
valuable source of knowledge for my research.
I would like to thank Prof. Jeffrey L. Petersen at West Virginia University and Dr.
Victor G. Young, Jr. at University of Minnesota for solving the crystal structures. And I
also would like to thank Prof. Stephen C. Bergmeier and his graduate student Fang Fang
for the valuable discussion about nitrene chemistry.
Also, I want to thank my labmates, faculty and staff from the Department of
Chemistry and Biochemistry, my research work has become much easier with generous
support from these people.
Last but not least, I would like to thank my deeply loved parents Xiuzhen Qiu and
Guoping Liang, who have given me the support and encouragement to complete my
Ph.D. in chemistry.
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TABLE OF CONTENTS
Page
Abstract ............................................................................................................................... 3
Dedication ........................................................................................................................... 5
Acknowledgments............................................................................................................... 6
List of Tables .................................................................................................................... 10
List of Figures ................................................................................................................... 12
List of Schemes ................................................................................................................. 15
Chapter 1: Introduction ..................................................................................................... 17
General Aspects ............................................................................................................ 17
C-H Bond Amination Reactions ................................................................................... 20
Aziridination of C=C Bonds and Applications of Aziridine ........................................ 26
Structures and Applications of Late Metal Imido Complexes ...................................... 30
References ..................................................................................................................... 43
Chapter 2: Synthesis and Characterization of Transition Metal Scorpionate Complexes 50
Introduction ................................................................................................................... 50
Experimental Details..................................................................................................... 51
Results and Discussion ................................................................................................. 61
Characterization of [(L)M(NCMe)3](BF4)n .................................................................. 63
A. X-ray Crystallography.......................................................................................... 63
B. Electronic Spectroscopy ....................................................................................... 74
C. 1H NMR Spectroscopy ......................................................................................... 85
D. FT-IR Spectroscopy ............................................................................................. 93
E. Magnetic Properties ............................................................................................ 101
References ................................................................................................................... 103
Chapter 3: Nitrene Transfer Catalysis Mediated by Transition Metal Scorpionate
Complexes....................................................................................................................... 108
Aziridination Reactions of Olefins ............................................................................. 110
Aziridination of para-Substituented Styrenes ............................................................ 118
C-H bond Amination of Tetrahydrofuran ................................................................... 121
C-H bond Amination of Aromatic Substrates............................................................. 127
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References ................................................................................................................... 131
Chapter 4: Masked Lewis Acid [Fe(NCMe)6](BF4)2 Catalyzed Cycloaddition Reactions
......................................................................................................................................... 134
[2+1+2] Cycloaddition of Alkenes with PhI=NTs ..................................................... 139
[3+2] Cycloadditon of Aziridine with Alkenes, Aldehydes, Ketones and Alkynes ... 144
Experimental Procedures for Chapter 3 and Chapter 4 .............................................. 151
References ................................................................................................................... 154
Chapter 5: Oxene and Nitrene Chemistry of Ni(0) Mediated by Tris(3,5-dimethylpyrazol1-yl)methane ................................................................................................................... 156
Experimental ............................................................................................................... 157
Results and Discussion ............................................................................................... 163
References ................................................................................................................... 179
Appendix 1: NMR Spectrum of 2 ................................................................................... 184
Appendix 2: NMR Spectrum of 52 ................................................................................. 185
Appendix 3: NMR Spectrum of 53 ................................................................................. 186
Appendix 4: NMR Spectrum of 17 ................................................................................. 187
Appendix 5: NMR Spectrum of 15 ................................................................................. 188
Appendix 6: NMR Spectra of 16 .................................................................................... 189
Appendix 7: NMR Spectrum of 12 ................................................................................. 192
Appendix 8: NMR Spectrum of 13 ................................................................................. 193
Appendix 9: NMR Spectrum of 14 ................................................................................. 194
Appendix 10: NMR Spectrum of 32 ............................................................................... 195
Appendix 11: NMR Spectra of 45 .................................................................................. 196
Appendix 12: NMR Spectrum of 39 and 40 ................................................................... 198
Appendix 13: NMR Spectrum of 43 and 44 ................................................................... 200
Appendix 14: NMR Spectrum of 41 and 42 ................................................................... 202
Appendix 15: NMR Spectrum of 37 and 38 ................................................................... 204
Appendix 16: NMR Spectrum of 35 and 36 ................................................................... 206
Appendix 17: NMR Spectrum of 34 and 35 ................................................................... 208
Appendix 18: NMR Spectrum of 22 ............................................................................... 210
Appendix 19: NMR Spectrum of 23 ............................................................................... 211
Appendix 20: NMR Spectrum of 19 ............................................................................... 212
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Appendix 21: NMR Spectra of 3 .................................................................................... 213
Appendix 22: NMR Spectra of 50 .................................................................................. 215
Appendix 23: NMR spectrum of 51................................................................................ 217
Appendix 24: NMR Spectra of 60 .................................................................................. 219
Appendix 25: NMR Spectra of 62 .................................................................................. 221
Appendix 26: NMR Spectra of 63 .................................................................................. 223
Appendix 27: NMR Spectra of 64 .................................................................................. 225
Appendix 28: NMR Spectrum of 69 ............................................................................... 227
Appendix 29: NMR Spectra of 65 and 66 ...................................................................... 229
Appendix 30: NMR Spectra of 67 .................................................................................. 231
Appendix 31: X-ray Crystallographic Data for Complex 2Mn ........................................ 233
Appendix 32: X-ray Crystallographic Data for Complex 2Ni ......................................... 238
Appendix 33: X-ray Crystallographic Data for Complex 3Fe ......................................... 243
Appendix 34: X-ray Crystallographic Data for Complex 3Co......................................... 247
Appendix 35: X-ray Crystallographic Data for Complex 4Fe ......................................... 251
Appendix 36: X-ray Crystallographic Data for Complex 5Ni ......................................... 256
Appendix 37: X-ray Crystallographic Data for Complex 6Ni ......................................... 262
Appendix 38: X-ray Crystallographic Data for Complex 7Ni ......................................... 268
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LIST OF TABLES
Page
Table 2.1: Selected bond distances (Å) and angles (deg) of 2Mn ....................................66
Table 2.2: Selected bond distances (Å) and angles (deg) of 2Ni .....................................67
Table 2.3: Selected bond distances (Å) and angles (deg) of 3Fe .....................................68
Table 2.4: Selected bond distances (Å) and angles (deg) of 3Co .....................................69
Table 2.5: Selected bond distances (Å) and angles (deg) of 4Fe .....................................70
Table 2.6: Selected average bond distances (Å) and angles (deg) for tris-acetonitrile
complexes .......................................................................................................................71
Table 2.7: Average M-N bond distances (Å) of metal salts [M(NCCH3)6]2+ .................71
Table 2.8: Fe-N≡C angles (deg) of complexes 3Fe and 4Fe .............................................73
Table 2.9: UV-Vis spectra data for Fe(II) complexes 1Fe-4Fe .........................................77
Table 2.10: UV-Vis spectra data for Co(II) complexes 1Co-4Co .....................................82
Table 2.11: UV-Vis spectra data for Ni(II) complexes 1Ni-4Ni .......................................84
Table 2.12: Chemical shifts for TpmMe,Me and TpMe,Me-supported complexes 1M and 3M
(M = Fe, Co, Ni) .............................................................................................................87
Table 2.13: Chemical shifts for TpmPh and TpPh,Me-supported complexes 2M and 4M
(M = Fe, Co, Ni) .............................................................................................................87
Table 2.14: FT-IR νCN absorption bands of [(L)M(NCMe)3](BF4)2 (1M-2M) .................95
Table 2.15: FT-IR νCN and νB-H absorption bands of [(L)M(NCMe)3]BF4 (3M-4M) ........95
Table 2.16: Effective magnetic moments (µ eff) of complexes 1M-4M in CD3CN at 295 K
by Evans NMR method .................................................................................................102
Table 2.17: UV-Vis, Magnetic Moments and FT-IR data for [MII(NCMe)n](BF4)2 ....103
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Table 3.1: Complexes 1M-4M and [Fe(CH3CN)6](BF4)2 catalyzed aziridination reactions
of styrene with PhI=NTs ...............................................................................................111
Table 3.2: 1Fe catalyzed aziridinations of styrene with PhI=NTs .................................114
Table 3.3: Olefin aziridinations mediated by 1Fe with PhI=NTs ..................................117
Table 3.4: Experimental kY/kH and log(kY/kH) values ....................................................119
Table 3.5: Complexes 1M-4M catalyzed amination of THF with PhI=NTs ..................123
Table 3.6: [TpmMe,MeFe(CH3CN)3] (BF4)2 (1Fe) catalyzed amination of cyclic alkane
substrates with PhI=NTs ...............................................................................................126
Table 3.7: Intermolecular C-H bond amination of aromatic substrates mediated by 1Fe
with PhI=NTs ................................................................................................................130
Table 4.1: [2+1+2] cycloaddition of olefins with PhI=NTs in the presence of unmasked
Lewis acid [Fe(NCMe)6](BF4)2 in CH2Cl2 ...................................................................142
Table 4.2: [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with various dipolarophiles
in the presence of unmasked Lewis acid [Fe(NCMe)6](BF4)2 in CH2Cl2.....................149
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LIST OF FIGURES
Page
Figure 1.1: Jacobsen’s proposed redox mechanism of copper catalyzed aziridination ..29
Figure 1.2: Molecular orbital diagram of a tetragonal metal-imido complex depicting
the π bonding interaction ................................................................................................31
Figure 1.3: Isolated and structurally characterized iron-imido complexes .....................34
Figure 1.4: Reactions of [(ArL)Fe(N(p-tBuC6H4)Cl] with toluene and styrene ..............39
Figure 1.5: Proposed catalytic cycle of the amination of toluene by [(AdL)FeCl(OEt2)]39
Figure 2.1: Thermal ellipsoid plot of the cationic part of 2Mn ........................................66
Figure 2.2: Thermal ellipsoid plot of the cationic part of 2Ni .........................................67
Figure 2.3: Thermal ellipsoid plot of the cationic part of 3Fe .........................................68
Figure 2.4: Thermal ellipsoid plot of the cationic part of 3Co .........................................69
Figure 2.5: Thermal ellipsoid plot of the cationic part of 4Fe .........................................70
Figure 2.6: Effects of scorpionate ligands on metal to nitrogen bond lengths ...............72
Figure 2.7: Space-filling overlay plot of 3Fe and 4Fe .......................................................73
Figure 2.8: UV-Vis spectra of Mn(II) complexes 1Mn, 2Mn and 4Mn ...............................76
Figure 2.9: UV-Vis spectra of Fe(II) complexes 1Fe, 2Fe, 3Fe and 4Fe .............................77
Figure 2.10: UV-Vis spectra of 3Fe showing the onset of spin crossover behavior ........78
Figure 2.11: UV-Vis spectra of Co(II) complexes 1Co, 2Co, 3Co and 4Co ........................81
Figure 2.12: UV-Vis spectrum of 3Co .............................................................................81
Figure 2.13: UV-Vis spectra of Ni(II) complexes 1Ni, 2Ni, 3Ni and 4Ni ...........................83
Figure 2.14: UV-Vis spectrum of 3Ni showing the absorption band assignments ..........83
Figure 2.15: 1H NMR spectra of TpmMe,Me-supported complexes 1Fe, 1Co and 1Ni ........88
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Figure 2.16: 1H NMR spectra of TpMe,Me-supported complexes 3Fe, 3Co and 3Ni ...........89
Figure 2.17: 1H NMR spectra of TpmPh-supported complexes 2Fe, 2Co and 2Ni .............90
Figure 2.18: 1H NMR spectra of TpPh,Me-supported complexes 4Fe, 4Co and 4Ni ............91
Figure 2.19: Graphical representation of complex 1Co in a dipolar double cone ............92
Figure 2.20: FT-IR spectra of [TpmMe,MeM(NCMe)3](BF4)2 (1M)..................................96
Figure 2.21: FT-IR spectra of [TpmPhM(NCMe)3](BF4)2 (2M).......................................97
Figure 2.22: FT-IR spectra of [TpMe,MeM(NCMe)3]BF4 (3M) .........................................98
Figure 2.23: FT-IR spectra of [TpPh,MeM(NCMe)3]BF4 (4M) .........................................99
Figure 2.24: FT-IR spectra of 2Ni and 4Ni, emphasizing the effect of ligand on the νCN
absorption bands ...........................................................................................................100
Figure 3.1: 1H NMR spectra of aziridination of styrene with PhI=NTs .......................113
Figure 3.2: Hammett plot of experimentally determined log(kY/kH) value vs. Hammett
para-substituent constant σp .........................................................................................119
Figure 3.3: 1H NMR spectrum: Competition reaction of styrene and p-nitrostyrene
mediated by 1Fe with PhI=NTs .....................................................................................120
Figure 3.4: 1H NMR spectrum: C-H bond amination products of competition reaction
of THF and THF-d8 catalyzed by 1Fe with PhI=NTs ....................................................125
Figure 5.1: Thermal ellipsoid plot of 5Ni ......................................................................173
Figure 5.2: 1H NMR spectra: A, 1:1 TpmMe,Me and [Ni0(COD)2]; B, free TpmMe,Me; C,
free COD .......................................................................................................................174
Figure 5.3: Thermal ellipsoid plot of 6Ni ......................................................................175
Figure 5.4: 1H NMR spectra: A, solvated 5Ni in wet CD3CN; B, 6Ni in CD3CN; C, 6Ni in
CD2Cl2; D, 7Ni in CD3CN; E, crude products including 8Ni from reaction of 1:1:1
[Ni0(COD)2]:TpmMe,Me:2-tBuSO2C6H4IO in THF, extracted into CDCl3.....................176
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Figure 5.5: UV-Vis-NIR spectra of solvated 5Ni in CH3OH, 6Ni in CH2Cl2 and 7Ni in
CH3CN ..........................................................................................................................177
Figure 5.6: Thermal ellipsoid plot of 7Ni ......................................................................178
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LIST OF SCHEMES
Page
Scheme 1.1: Transition metal catalyzed reactions of nitrene .........................................19
Scheme 1.2: Proposed mechanism for transition metal mediated aziridination of olefins,
amination of sp3 C-H bonds and aromatic C-H bonds ....................................................19
Scheme 1.3: Schematic representation of the rebound mechanism of cytochrome P450
.........................................................................................................................................21
Scheme 1.4: Copper(0) catalyzed reaction of benzenesulfonyl azide and cyclohexene.21
Scheme 1.5: Metal catalyzed intermolecular amination of cyclohexane ........................23
Scheme 1.6: Metal catalyzed intramolecular amination .................................................23
Scheme 1.7: Proposed mechanism for nitrene insertion into C–H bond of cyclohexane
mediated by a Mn catalyst ..............................................................................................23
Scheme 1.8: TpBr3Cu(NCMe) catalyzed aromatic and benzylic C-H bond aminations..25
Scheme 1.9: AuCl3 catalyzed aromatic and benzylic C-H bond aminations ..................25
Scheme 1.10: Aziridination of cyclooctene with [(TMP)Mn≡N]...................................29
Scheme 1.11: Phenylaziridine as a masked 1,3-dipole in reaction with alkene .............29
Scheme 1.12: Reactions of isolated iron-imido species..................................................34
Scheme 1.13: Intramolecular and intermolecular Hydrogen Atom Transfer (HAT)
reactivity of an isolable iron(III)-imido complex [(MeL)Fe(NAd)(tBupy)] ....................37
Scheme 1.14: HAT reaction of a putative iron(IV)-imido species .................................37
Scheme 1.15: Aromatic C-H bond functionalizations by [(6-PhTPA)Fe(NCMe)2]2+ ....37
Scheme 1.16: Synthesis of iron(III)-imido complex [(ArL)Fe(N(p-tBuC6H4)Cl] ...........39
Scheme 1.17: Reaction of [(PhBP3)Co≡N-p-tolyl] with CO, and intramolecular C-H
bond insertion of [(TptBu,Me)Co=NAd] ............................................................................41
16
Scheme 1.18: Reactivity of terminal Ni-imido complex [(Me3NN)Ni=NAd] ...............42
Scheme 1.19: Nitrene, phosphinidene and carbene transfer reactivities of diphosphine
ligand supported Ni(II) complexes .................................................................................42
Scheme 2.1: Synthesis of complexes 1M-4M (M = Mn, Fe, Co, Ni) ...............................62
Scheme 3.1: Azirdination of styrene using TsNH2 and PhI(OAc)2 as nitrene source
catalyzed by [TpmMe,MeFe(CH3CN)3](BF4)2 (1Fe) .........................................................115
Scheme 3.2: Competition reaction of styrene and para-substituted styrene mediated by
1Fe with PhI=NTs ..........................................................................................................119
Scheme 4.1: [2+1+2] cycloaddition reaction of styrene with PhI=NTs in CH2Cl2
catalyzed by [Fe(NCMe)6](BF4)2..................................................................................138
Scheme 4.2: [2+1+2] cycloaddition reaction of para-substituted styrene in CH2Cl2
mediated by unmasked Lewis acid [Fe(NCMe)6](BF4)2 with PhI=NTs .......................143
Scheme 4.3: Formal [3+2] cycloaddition of aziridine 2 with various dipolarophiles
mediated by [Fe(NCMe)6](BF4)2 ..................................................................................145
Scheme 4.4: Hydrolysis of 1,3-oxazolidine derivative 64 to 1,2-amino alcohol 69 .....145
Scheme 4.5: Proposed mechanism showing the formation of 2-pyrroline derivatives by
the cycloaddition of aziridine 2 and phenylacetylene 57 with [Fe(NCMe)6](BF4)2 .....150
17
CHAPTER 1: INTRODUCTION
General Aspects
C-C, C=C and C-H bonds are ubiquitous in organic molecules, pharmaceuticals
and biological compounds.1 Thus, the range of substrates for bond functionalization is
virtually unlimited. Development of transition metal catalyzed bond formation reactions
is fundamentally important, and the nitrene transfer reaction has great synthetic
promise.2-9 This process generally involves the generation of a metal-imido intermediate
in the presence of a nitrene precursor and a transition metal catalyst [LnM]. This metalimido intermediate then undergoes reaction with an organic substrate (Scheme 1.1),3,10,11
typically more selectively than the free nitrene. Two major modes of reactivity have been
observed for metal-imido intermediates. Addition of the nitrene fragment to a C=C bond
in an unsaturated organic substrate such as olefin gives rise to an aziridine product. This
process produces a valuable strained three-membered ring containing one nitrogen atom,
which is an important moiety found in many bioactive natural products, and also serves
as a significant synthetic intermediate in organic synthesis and in pharmaceuticals, owing
to facile ring opening of the strained ring.12-14 The aziridination reaction is usually
postulated to proceed via a mechanism with the formation of a radical intermediate (route
A in Scheme 1.2).15 The other reaction mode of a metal-imido intermediate is C-H bond
amination. This reactivity, which sometimes accompanies aziridination reactions, is the
insertion of the nitrene fragment into a C-H bond of the organic substrate, generating an
amine product.3 The amination of an sp3 C-H bond is usually proposed to proceed via a
stepwise hydrogen atom abstraction and radical rebound mechanism, with the formation
18
of a carboradical intermediate, as illustrated in route B in Scheme 1.2.15,16 On the other
hand, the direct amination of an aromatic (sp2) C-H bond is quite different. An
electrophilic addition mechanism is usually involved in this amination process, where the
amination product is formed by electrophilic addition of nitrene radical to a phenyl C=C
bond (route C in Scheme 1.2). Therefore, both C-H bond amination and C=C bond
azridination offer a way to introduce a nitrogen atom into an organic compound. Owing
to the ubiquitous nature of C-H bonds in most organic molecules, C-H bond amination
reactions would allow for the insertion of nitrene group into many organic compounds.
On the other hand, traditional synthetic approaches of constructing C-N bonds generally
rely on the addition or substitution of a nitrogen nucleophile to a carbon electrophile.
These reactions often require the presence of polarized double bonds such as C=O, or the
presence of reactive functional groups such as a C-X bond (X = halogen, OSO2CF3, OTs,
etc).1 The consequences of these reaction conditions include increasing the number of
steps, formation of byproducts and poor atom economy. Hence, transition metal catalyzed
C-H amination reactions would be of great synthetic value, as this method directly
constructs C-N bonds, thereby shortening multi-step synthesis.
However, despite the ubiquity of C-H bonds, they are rarely considered as
synthons in the scope of organic chemistry. There are two major challenges associated
with C-H functionalization reactions. First, unfunctionalized C-H bonds are nonpolar,
with bond dissociation energies typically between 88 – 113 kcal/mol; such strong σ
bonds suppress the reactivity of C-H bonds compared to relatively more reactive C-X
bonds.4 Furthermore, the chemical similarity of C-H bonds means the ability to
19
regioselectively activate a single given C-H bond within a complex organic molecule is
problematic.1 For these reasons, the successful development of a practical and efficient
C-N bond-forming reaction through direct C-H bond functionalization would be of
fundamental importance for the synthesis of natural products, pharmaceuticals and other
relevant targets.
Scheme 1.1. Transition metal catalyzed reactions of nitrene.3
Scheme 1.2. Proposed mechanism for transition metal mediated aziridination of olefins
(route A), amination of sp3 C-H bonds (route B) and aromatic C-H bonds (route C)
20
C-H Bond Amination Reactions
As mentioned above, functionalization of unactivated C-H bonds represents a
significant challenge in synthetic chemistry.1,17 In nature, oxidation reactions such as C-H
bond functionalization generally involve enzymes as catalysts.17 This is primarily
achieved by utilizing iron-containing enzymes such as cytochrome P450 as the catalyst
and dioxygen as the terminal oxidant. Many studies have provided insight into the
mechanism of C-H functionalization reactions catalyzed by the cytochrome P450 family.
The consensus mechanism for the oxidation reaction, suggested by Groves and coworkers, is the rebound mechanism, shown in Scheme 1.3.18-20 A transient terminal
iron(IV)-oxo porphyrin radical species (compound I), which is formally oxidized by two
electrons relative to the ferric resting state, is the key intermediate in the C-H
functionalization process.20-22 An alkyl radical and an iron(IV)-hydroxo intermediate
(compound II) are formed from the initial hydrogen atom abstraction from an alkane
(RH) substrate by the active iron(IV)-oxo species, then the alkyl radical combines with
the iron(IV)-hydroxo intermediate to generate an iron(III)-alcohol complex, which then
releases the alcohol and restores the resting state, an iron(III)-OH2 complex.20
21
Scheme 1.3. Schematic representation of the rebound mechanism of cytochrome P45020
Scheme 1.4. Copper(0) catalyzed reaction of benzenesulfonyl azide and cyclohexene.23
22
Inspired by biological C-H bond functionalization reactions, especially heme iron
catalyzed C-H bond hydroxylation reactions, C-H bond amination reactions utilizing
transition metal complexes as catalysts have received a lot of attention from many
workers.4,5,16 In 1967, Kwart and Khan first proposed a copper-imido species obtained
from the decomposition of benzenesulfonyl azide in the presence of powdered copper
metal in cyclohexene. This reaction gave numerous products (Scheme 1.4), most of
which were consistent with the formation of a copper-imido species as a reactive
intermediate.23 In 1982, Breslow and co-workers first reported the catalytic transfer of
nitrene to alkanes (Scheme 1.5).24 Intermolecular amination of cyclohexane was achieved
by using (p-toluenesulfonyl)iminophenyliodinane (PhI=NTs, Ts = p-toluenesulfonyl) as
nitrene source in the presence of either [Mn(TPP)Cl] or [Fe(TPP)Cl] (TPP = 5, 10, 15,
20-tetraphenylporphyrin) as metal catalyst, although the yields of cyclohexane
sulfonamides were not synthetically useful (3.1- 6.5%). Intramolecular benzylic C-H
bond nitrene insertion of N-(2,5-diisopropylbenzenesulfonyl)iminophenyliodinane was
reported by the same group in 1983, with a variety of catalysts (Scheme 1.6).25 The
intramolecular amination reaction turned out to be much more efficient, achieving the
cyclic sulfonamide product with up to 86% yield. Then Breslow and co-workers also
reported the insertion of a nitrene fragment into a C-H bond of cyclohexane, with
cytochrome P450 as the catalyst. It is noteworthy that a high-valent iron-imido complex
was proposed as the key intermediate.26
23
Scheme 1.5. Metal catalyzed intermolecular amination of cyclohexane.24
Scheme 1.6. Metal catalyzed intramolecular amination.25
Scheme 1.7. Proposed mechanism for nitrene insertion into C–H bond of cyclohexane
mediated by a Mn catalyst.27
24
Following the seminal work of Breslow and co-workers, Mansuy and co-workers
achieved the amination of saturated C-H bonds of cyclohexane and adamantane in the
presence of PhI=NTs as a nitrene precursor and a series of iron and manganese porphyrin
complexes as the catalyst, with 3.1-15% yields for amination of cyclohexane and 19-56%
yields for adamantane, respectively. Notably, an H-atom abstraction and radical rebound
mechanism involving a reactive high valent Mn-imido intermediate was proposed for the
[Mn(TDCPP)(CF3SO3)] (TDCPP = 5, 10, 15, 20-tetrakis{2,6-dichlorophenyl}porphyrin)
catalyzed amination reaction (Scheme 1.7).27,28
Besides the C-H bond amination reactions mentioned above, other impressive
reactivity using Mn,29 Co,30 Cu31,32 and Ag33 complexes have also been demonstrated to
induce similar nitrene insertion to C-H bonds. However, many of the C-H bond
amination reactions reported were achieved by insertion of a nitrene group into allylic or
benzylic C-H bonds, or through intramolecular C-H bond amination processes,34 while
the analogous amination of aromatic C-H bonds is less well explored.2
Pérez and co-workers recently demonstrated the catalytic nitrene insertion into CH bonds of cyclohexane, toluene, mesitylene and benzene using a Cu(I) complex
[TpBr3Cu(NCMe)] (TpBr3 = hydrotris{3,4,5-tribromopyrazolyl}borate) as catalyst.35 The
Cu(I) catalyst successfully promoted the nitrene insertion into a C-H bond of benzene
with 40% yield at room temperature (eq. 1 in Scheme 1.8). However, when toluene and
mesitylene were used as the reaction substrates, the functionalization reactions
exclusively took place onto benzylic C-H bonds, with yields up to 95% (eqs. 2, 3 in
Scheme 1.8).
25
NHTs
PhI=NTs
(eq. 1)
TpBr3Cu(NCMe) (5 mol%), rt
40% yield
Me
PhI=NTs
Br3
Tp
(eq. 2)
NHTs
Cu(NCMe) (5 mol%), rt
> 95% yield
Me
Me
Me
PhI=NTs
NHTs
(eq. 3)
TpBr3Cu(NCMe) (5 mol%), rt
Me
Me
> 95% yield
Scheme 1.8. [TpBr3Cu(NCMe)] catalyzed aromatic and benzylic C-H bond aminations.35
AuCl3 (2 mol%)
(eq. 1)
PhI=NNs
NHNs
AuCl3 (2 mol%)
HCl
HCl
PhI=NNs
AuCl2
AuCl2
AuCl3
NHNs
PhI=NNs
for weaker
benzylic C-H
NHNs
PhI=NNs
HCl
AuCl2
Scheme 1.9. AuCl3 catalyzed aromatic and benzylic C-H bond aminations.36
26
The direct insertions of the nitrene fragment (NNs, Ns = p-nitrobenzenesulfonyl)
into the C-H bonds of several alkyl substituted aromatic substrates were carried out by He
and co-workers with AuCl3 as the catalyst.36 This was the first example introducing a
gold complex as a catalyst to induce the transformation of C-H bonds into C-N bonds.
Surprisingly, amination of methyl-substituted aromatics such as 1,3,5-trimethylbenzene
gave solely the aromatic C-H bond insertion products (eq. 1 in Scheme 1.9), without any
observation of benzylic C-H bond functionalization products. Only when isopropyl
groups with weaker benzylic C-H bonds were present, these were functionalized as well
as aromatic C-H bonds. With isotope labeling studies, they proposed that the unique
chemoselectivity toward aromatic C-H bond functionalization was due to the formation
of arylgold(III) species. This unique mechanism is different from those mentioned above,
where high valent metal-imido species were proposed to be key intermediates. In this
catalytic cycle, the aromatic C-H bond is activated by the gold center, to form an
arylgold(III) intermediate, along with elimination of HCl. The nitrene precursor
(PhI=NNs) is then activated through the interaction with the arylgold(III) intermediate.
Finally, HCl reacts with the adduct, giving amine product and regenerating the AuCl3
catalyst (Scheme 1.9).
Aziridination of C=C Bonds and Applications of Aziridine
Since Gabriel first discovered the smallest nitrogen-containing heterocyle in 1888,
aziridines have gained considerable attention as synthetic targets as well as useful
synthetic building blocks in organic synthesis and pharmaceutical chemistry.37 Attracted
by the unique reactivity and high chemical and biological activity of the three-membered
27
ring, synthetic chemists have extensively explored the various strategies for aziridine ring
formation.12,14 Although myriad achievements have been made on transition metal
catalyzed oxygen atom transfer reactions to C=C bonds to form epoxides,38,39 the
analogous nitrene transfer reactions to form aziridines have been less well developed. All
this was changed with the significant discovery of PhI=NTs ({p-toluenesulfonyl}iminophenyliodinane) and its analogues by Yamada and co-workers in 1975.40 Since
intense efforts have been contributed to the advancement of transition metal mediated
aziridination reactions.2
In 1984, Mansuy and co-workers reported the first example of an iron complex
catalyzed azirdination reaction, using [Fe(TTP)Cl] (TTP = 5,10,15,20-tetrakis{4methylphenyl}porphyrin).10 A significant advance in this area was the seminal work
achieved by Evans and co-workers in 1994: nitrene transfer to a wide variety of olefins
was obtained using Cu(I) or Cu(II) salts as catalyst and PhI=NTs as nitrene precursor.41
Moreover, Evans and co-workers achieved the asymmetric aziridination of transcinnamate esters catalyzed by CuOTf with the chiral ligand PhBOX ({S,S}-2,2’isopropylidene-bis{4-phenyl-2-oxozoline}) as a supporting ligand and PhI=NTs as
nitrene precursor.42 Jacobsen and co-workers also achieved the asymmetric aziridination
of various alkenes with chiral diimine ligand supported Cu(I) catalysts. Notably,
mechanistic studies suggested that the (diimine)copper(I) catalyzed aziridination
reactions proceed through a high-valent Cu(III)-imido intermediate (Figure 1.1).43,44
Recently, Abu-Omar and co-workers reported nitrene transfer from ArI=NTs (Ar = 2{tert-butylsulfonyl}benzene, Ts = p-toluenesulfonyl) to styrene substrates catalyzed by a
28
Mn(III) corrole complex [(TPFC)Mn] (TPFC = 5,10,15-tris{pentafluorophenyl}corrole).
Significantly, they revealed that the high-valent Mn(V)-imido species [(TPFC)Mn=NTs]
is not the nitrene transfer reagent; double-labeling experiments suggested that the oxidant
in this aziridination reaction is an iminoiodinane (ArI=NTs) adduct of a pre-formed imido
Mn(V) species, [(TPFC)Mn(NTstBu)(ArINTs)].45
Groves
and
co-workers
reported
a
Mn(V)-nitrido
porphyrin
complex
[(TMP)Mn≡N] (TMP = 5,10,15,20-tetramesityl-porphyrin), which forms a Mn(V)acylimido trifluoroacetate complex when reacted with trifluoroacetic anhydride. Notably,
this Mn(V)-acylimido species exhibited stoichiometric transfer of the nitrene moiety
CF3CON to cis-cyclooctene to furnish the N-trifluoroacetyl-protected aziridine (Scheme
1.10).46 Various other transition metals have also been employed in olefin aziridination
reactions including Fe,47-51 Co,52 Ag,6,53 Au,54 Ru15 and Re55.
Aziridines exhibit a wide range of useful reactivities including regioselective
nucleophilic ring opening, which harnesses the release of ring strain.13,14 Recently,
transformations of aziridines to five-membered nitrogen-containing heterocycles through
formal [3+2] cycloaddition reactions have been described.56 Cycloaddition reactions of
aziridines with CO2 and CS2 forming 1,3-oxazolidine-2-ones and urethanes, respectively,
have been reported by Endo and co-workers.57 Alkenes,58-60 alkynes,61,62 carbonyls and
nitriles63-65 have also been employed as dipolarophiles leading to the formation of
valuable five-membered nitrogen-containing heterocycles.
29
Figure 1.1. Jacobsen’s proposed redox mechanism for copper catalyzed aziridination
(Adapted with permission from ref. 43, Copyright [1995] American Chemical Society)
Scheme 1.10. Aziridination of cyclooctene with [(TMP)Mn≡N] (Adapted with
permission from ref. 46, Copyright [1983] American Chemical Society).
Scheme 1.11. Phenylaziridine as a masked 1,3-dipole in reaction with alkene (Adapted
with permission from ref. 59, copyright [2000] John Wiley and Sons).
30
Mann and co-workers first reported the formation of a unique 1,3-dipole
generated from 2-phenyl-N-tosylaziridine through C-N bond breaking in the presence of
Lewis acid.59 The conversion of 2-phenyl-N-tosylaziridine into substituted pyrrolidines
have been achieved through the formal [3+2] cycloaddition reactions of 2-phenyl-Ntosylaziridine with inactivated alkene substrates, in the presence of a stoichiometric
amount of BF3·Et2O (Scheme 1.11). Singh and co-workers have demonstrated analogous
[3+2] cycloaddition reactions of aryl substituted N-tosylaziridines with carbonyls
(aldehydes or ketones) and nitriles as dipolarophiles, in the presence of a stoichiometric
amount of BF3·Et2O or a catalytic amount of Zn(OTf)2.63 The [3+2] cycloaddition
reactions proceeded smoothly in CH2Cl2, converting carbonyls or nitriles into
oxazolidines or imidazolines with moderate to good yields. Nguyen and co-workers also
achieved the analogous conversion of carbonyls into 5-alkyl-1,3-oxazolidines through
cycloaddition reactions of carbonyls with less reactive 2-alkyl substituted-Ntosylaziridines in the presence of 20 mol% of Sc(OTf)3.66 Cycloadditions of alkynes with
aziridines affording 2-pyrroline derivatives were also reported by Wender62 and Wang
groups61 with AgSbF6 and FeCl3 as catalysts, respectively. For a general review of πnucleophiles, see Krake and Bergmeier.12
Structures and Applications of Late Metal Imido Complexes
Terminal imido complexes of the late first row transition metals are usually
implicated as intermediates in transition metal catalyzed nitrene transfer reactions.67,68
However, little was known about the structure of the presumed metal-imido
This is typically ascribed to the lack of empty d orbitals of late transition metals available
31
to accept π donation from an imido moiety (NR).68,69 The bonding of the imido ligand
with metal d orbitals can be explained by molecular orbital theory in a tetragonal
geometry as depicted in Figure 1.2.68 Considering the principal axis (z) to lie along the
M-N bond, the π bonds of metal-imido species are formed by the interaction of the metal
dxz, dyz orbitals and the N atom px, py orbitals. Therefore, for productive π bonding to
occur, the metal must have empty d orbitals of π symmetry to accept donation from the
imido moiety, This is true for early and middle transition metals, since most of the d
orbitals of these metals are empty; therefore, it is not surprising that high-valent early
transition metal-imido species are stable and well explored.68,69
Figure 1.2. Molecular orbital diagram of a tetragonal metal imido complex depicting the
π bonding interaction (Adapted with permission from ref. 68, copyright [2003] Elsevier)
32
Although iron-imido species were implicated as nitrene transfer intermediates,25 it
was not until the year 2000 that Lee and co-workers isolated the first stable and
structurally characterized terminal iron(IV)-imido complex.70 The reaction of ferric
chloride and lithium t-butylamide gave rise to a tetranuclear iron cluster in very low
yield. This tetranuclear iron cluster contains three iron(III) and one iron(IV) centers.
These four iron centers are bridged by four t-butylimide ligands and the iron(IV) center
has a terminally bonded t-butylimide ligand (Figure 1.3).
Since then, several stable, structurally characterized examples of terminal ironimido complexes have been reported (Figure 1.3).71 Similar to the synthesis of
mononuclear cobalt-imido species,72 Peters and co-workers reported the first example of
a mononuclear iron(III)-imido complex, featuring a tetrahedral iron center supported by
bulky tris(phosphino)borate ligand.73 This iron(III)-imido complex was prepared via twoelectron oxidative nitrene group transfer from an aryl azide, using a low-valent iron(I)
complex. Subsequently, the Peters group and the Smith group reported mononuclear
iron(IV)-imido
complexes,
featuring
tetrahedral
iron
centers
supported
by
bis(phosphine)-pyrazolylborate74 and tris(carbene)borate ligands,75 respectively. These
two iron complexes were prepared in a fashion similar to Peters’ iron(III)-imido complex.
The iron(I) precursors were treated with aryl azides to give the corresponding iron(III)imido complexes, which were further oxidized to give iron(IV)-imido complexes. A
highly distorted square planar terminal iron(III)-imido complex [(iPrPDI)Fe=NAr] (iPrPDI
= {2,6-iPr2C6H3N=CMe}2C5H3N) was reported by Chirik and co-workers.76 And then
Power and co-workers reported a bis(imido)iron(V) complex with trigonal planar
33
geometry via the reaction of a sterically encumbered iron(I) precursor and aryl azide
N3(1-Ad).77
The iron(III)-imido complexes have been demonstrated to be able to undergo
nitrene transfer reactions and hydrogenation reactions, but no aziridination or C-H bond
amination reactivity. Treatment of the iron(III)-imido complex [(PhBP3)Fe≡N-p-tolyl]
with carbon monoxide (CO) at room temperature immediately and quantitatively gave ptolyl isocyanate O=C=N-p-tolyl and iron(I) byproduct [(PhBP3)Fe(CO)2] (eq. 1 in
Scheme 1.12).73 [(PhBP3)Fe≡N-p-tolyl] also represents the first example of a metal-imido
complex that can undergo hydrogenation reactions.78 It was found that the exposure of
[PhBP3]Fe≡N-p-tolyl to one atmosphere of hydrogen gas in benzene for three hours gave
an iron(II)-amido complex [PhBP3]Fe(NH-p-tolyl) as the major product at room
temperature. Prolonged hydrogenation of [PhBP3]Fe≡N-p-tolyl in benzene for three days
led to the formation of a new diamagnetic compound through the partial hydrogenation of
the benzene solvent (eq. 2 in Scheme 1.12). The iron(III)-imido complex (iPrPDI)Fe=NAr
was also found to react with hydrogen gas to give an iron-dihydrogen species
(iPrPDI)Fe(H2), with aniline as organic product (eq. 3 in Scheme 1.12).76
34
t
Bu
0 or +
N
t
Fe
N
N
Bu
t
Bu
t
Bu
Fe
Fe
N
Ph2P
Cl
Cl
Ph
PPh2
Ph
Fe
Fe
Cl
Ad
N
Ar
N
P
Bu
Lee's iron-imido cubane
R = H, Me
Peters' iron(III)-imido
Peters' iron(III)- and iron(IV)-imido
0 or +
Ad
N
Ad
Ad
N
Ar
N
N
Ar
N
Ar Fe
N
Fe
N
Ar N
N Ar
Fe
N
N N
B
Bu t
Bu
P tBu
Ph
Ar = p-tolyl
Bu
t
B
R
Ph
t
P
N
N
B
N
Fe
t
R
Ar
Ar
iPr
iPr
N
Ar
Ph
Ar = 2, 6-iPr2C6H3
Ar = 2, 4, 6-iPr2C6H3
Chirik's iron(III)-imido
(iPrPDI)Fe=NAr
Power's bis(imido)iron(V)
Ar = Mes
Smith's iron(III)- and iron(IV)-imido
Figure 1.3. Isolated and structurally characterized iron-imido complexes.70,71,73-77
Ar
N
OC
Ph
PPh2
Ph
P
Ph2P
CO
Fe
Fe
Ph
CO(g)
P
Ph2P
p-TsN3
Ph
PPh2
ArNCO
(eq. 1)
B
B
Ar = p-tolyl
Ph
Ph
H
Ar
Ar
N
Fe
Ph
Ph2P
P
H
NH
Fe
Ph
PPh2
1 atm. H2
rt, 3h
benzene
B
Ph2P
P
1 atm. H2
rt, 3d
benzene
B
Ar = p-tolyl
Ph
Fe
Ph
PPh2
Ph
Ph
Ph2P
P
B
Ph
Ph
Ph
PPh2
ArNH2
(eq. 2)
NH2
1 atm. H2
N
Ar N
Fe
NAr
N Ar
N
Ar N
Fe
H
H
N Ar
(eq. 3)
Rn
Scheme 1.12. Reactions of isolated iron-imido species (Adapted with permission from
ref. 71, copyright [2011] Springer).71,73,76,78
35
The hydrogen atom transfer (HAT) reactivity of iron-imido complexes has been
less well investigated than their oxo counterparts.79 Recently, Holland and co-workers
reported the first isolated iron(III)-imido complex that was able to accomplish both
intramolecular and intermolecular HAT reactions, suggested by large substrate kinetic
isotope effects.80 The terminal iron(III)-imido species [(MeL)Fe(NAd)(tBupy)] (MeL = βdiketiminate ligand, 2,4-bis{2,6-diisopropylphenylimido}pentyl) was decomposed to
form an iron(III)-amido species [(Me*L)Fe(NHAd)(tBupy)] within a few hours at room
temperature. The ligand was proposed to undergo intramolecular C-C bond coupling via
HAT reaction (eq. 1 in Scheme 1.13). Treatment of [(MeL)Fe(NAd)(tBupy)] with 1,4cyclohexadiene rapidly afforded an iron(II)-amido species [(MeL)Fe(NHAd)(tBupy)] and
benzene at -51 oC (eq. 2 in Scheme 1.13). The intermolecular HAT reaction of
[(MeL)Fe(NAd)(tBupy)] was limited to those substrates that contain weak C-H bonds.
When hydrocarbons with stronger C-H bonds such as toluene (benzylic C-H BDE ~89
kcal/mol) were present, intramolecular HAT reactivity was observed instead of an
intermolecular reaction.
Borovik and co-workers isolated an iron(III)-amido species, formed from the
reaction of an iron(II) complex with p-tolyl azide (p-tolN3) in dimethylacetamide (DMA).
This iron(III)-amido species was proposed to form from the intermolecular hydrogen
atom abstraction of DMA solvent with the putative iron(IV)-imido intermediate (Scheme
1.14).81 Although iron-imido complexes mentioned above displayed reactivities toward
hydrogen atom transfer and/or nitrene group transfer, the studies of iron-imido
intermediates involved in iron catalyzed C-N bond formation reactions are rare. Que and
36
co-workers reported an aromatic amination reaction on the ligand when they treated
tridentate
iron(II)
complex
[(6-PhTPA)Fe(NCMe)2](ClO4)2
(TPA
=
tris{2-
pyridylmethyl}amine) with solid PhI=NTs.82 The amination reaction was proposed to
proceed via a high valent iron(IV)-imido intermediate, which then gave an iron(III)amido complex after hydrogen atom abstraction (Scheme 1.15).
37
Scheme 1.13. Intramolecular (eq.1) and intermolecular (eq. 2) Hydrogen Atom Transfer
(HAT) reactivity of an isolable iron(III)-imido complex [(MeL)Fe(NAd)(tBupy)] (Adapted
with permission from ref. 80, Copyright [2011] American Chemical Society).
Scheme 1.14. Hydrogen atom abstraction reaction of a putative iron(IV)-imido species.81
Scheme 1.15. Aromatic C-H bond functionalizations by [(6-PhTPA)Fe(NCMe)2]2+.82
38
Only recently was the isolation and structural characterization of a reactive
iron(III)-imido complex, which was proved to be the key intermediate in catalyzed
amination and aziridination reactions, described by Betley and co-workers.16 They found
that treatment of [(ArL)FeCl] (ArL, 1,9-Ar2-5-mesityl-dipyrromethene, Ar = 2,4,6Ph3C6H2) with aryl azide p-tBuC6H4N3 afforded a terminal iron(III)-imido complex
[(ArL)Fe(N(p-tBuC6H4)Cl] (Scheme 1.16). Theoretical analyses of the iron(III)-imido
species [(ArL)Fe(N(p-tBuC6H4)Cl] suggested that this species contains a high spin
iron(III) (S = 5/2) center, which is antiferromagnetically coupled to an imido-based
radical (S = 1/2). Therefore the total spin of this iron species is S = 2. [(ArL)Fe(N(pt
BuC6H4)Cl] was found to be able to effectively insert the nitrene fragment into the C-H
bond of toluene as well as transfer the nitrene moiety to C=C bond of styrene (Figure
1.4). The unique reactivity of [(ArL)Fe(N(p-tBuC6H4)Cl], which is distinct from other
isolated iron-imido complexes, is presumably due to the high spin nature of the complex
and the radical character of the nitrene moiety. Catalytic amination of toluene and
aziridination of styrene were also achieved using the iron(II) precursor [(AdL)FeCl(OEt2)]
and adamantyl azide. The kinetic isotope effect study of C-H bond amination of toluene
provided kH/kD = 12.8(5). This KIE value suggested an H atom abstraction mechanism for
the C-H bond amination of toluene catalyzed by [(AdL)FeCl(OEt2)] (Figure 1.5).
39
Scheme 1.16. Synthesis of terminal iron(III)-imido complex [(ArL)Fe(N(p-tBuC6H4)Cl]
(Adapted with permission from ref. 16, Copyright [2011] American Chemical Society)
Figure 1.4. Reactions of [(ArL)Fe(N(p-tBuC6H4)Cl] with toluene and styrene (Adapted
with permission from ref. 16, Copyright [2011] American Chemical Society).
Figure 1.5. Proposed catalytic cycle for the amination of toluene by [(AdL)FeCl(OEt2)]
(Adapted with permission from ref. 16, Copyright [2011] American Chemical Society)
40
Besides iron-imido species, other imido complexes of metals such as cobalt and
nickel have also been isolated. Peters and co-workers isolated a terminal Co(III)-imido
complex, [(PhBP3)Co≡N-p-tolyl] supported by bulky tris(phosphino)borate ligand
PhBP3, by using the same synthetic strategy as for preparing the iron(III)-imido
complex.72 Notably, this Co(III)-imido species also transfers its imide group from cobalt
to CO gas, releasing the free isocyanate O=C=N-p-tolyl (eq. 1 in Scheme 1.17). Theopold
and co-workers were also able to isolate a stable terminal Co(III)-imido species
[(TptBu,Me)Co=NAd], by treating a THF solution of [(TptBu,Me)Co(N2)] with one
equivalent of adamantyl azide (AdN3) at room temperature. [(TptBu,Me)Co=NAd] was also
found to deliver the imide moiety to CO, forming free isocyanate O=C=NAd.
Interestingly, they found that heating a solution of [(TptBu,Me)Co=NAd] at 40ºC in the
presence of ethylene, the intramolecular insertion of the imide moiety NAd of
[(TptBu,Me)Co=NAd] into a C-H bond of one of the tert-butyl groups of the Tp ligand was
observed, while the olefin was not functionalized (eq. 2 in Scheme 1.17).83 Warren and
co-workers reported the isolation of diketiminate ligand supported terminal Co(III)-imido
complex [(Me2NN)Co≡NAd] (Ad = 1-adamantyl). However, in contrast to Peters and
Theopold’s terminal Co(III)-imido species, Warren’s imido complex exhibited no nitrene
transfer reactivity.84
Warren and co-workers demonstrated stoichiometric hydrogen atom transfer with
a isolated diketiminate supported terminal Ni(III)-imido complex, [(Me3NN)Ni=NAd].
[(Me3NN)Ni=NAd] rapidly reacts with 1,4-cyclohexadiene, giving a Ni(II)-amide
complex, [(Me3NN)Ni-NHAd]. [(Me3NN)Ni=NAd] was also found to be able to deliver
41
an imido group to various substrates such as CO, CNBut, and PMe3, affording
AdN=C=NBut and Me3P=NAd, respectively, in good yields (Scheme 1.18).85 Hillhouse
and co-workers reported the crystal structure of bulky diphosphine ligand supported
diamagnetic
Ni(II)-imido
complex
[(dtbpe)Ni=NAr]
(dtbpe
=
1,2-bis{di-tert-
butylphosphino}ethane; Ar = 2,6-di-isopropylphenyl). It is worth noting that this
diphosphine ligand was also found to stabilize isolobal phosphinidene and carbene
groups, forming analogous diamagnetic Ni(II) complexes, [(dtbpe)Ni=P(dmp)] (dmp =
2,6-dimesitylphenyl) and (dtbpe)Ni=CPh2, respectively. Significantly, they discovered
that these isolated imido, phosphinidene and carbene complexes of Ni(II) could undergo
group transfer to ethylene, forming the three-membered ring compounds, aziridine,
phosphirane and cyclopropane, respectively (Scheme 1.19).86
Scheme 1.17. Reaction of [(PhBP3)Co≡N-p-tolyl] with CO (eq.1), and intramolecular CH bond insertion of [(TptBu,Me)Co=NAd] (eq.2).72,83
42
Scheme 1.18. Reactivity of terminal Ni-imido complex [(Me3NN)Ni=NAd] (Adapted
with permission from ref. 85, Copyright [2005] American Chemical Society).
Scheme 1.19. Nitrene, phosphinidene and carbene transfer reactivities of diphosphine
ligand supported Ni(II) complexes (Adapted with permission from ref. 86, Copyright
[2003] American Chemical Society).
43
This work will focus on olefin aziridinations and C-H bond aminations catalyzed
by transition metal complexes. We employed N3-tripod scorpionate ligands to support
different transition metal centers. Therefore, complexes [(L)M(NCCH3)3](BF4)n (L =
tris{3,5-dimethylpyrazol-1-yl}methane, TpmMe,Me, M = Mn, Fe, Co, Ni, n = 2; L = tris{3phenylpyrazol-1-yl}methane, TpmPh, M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5dimethylpyrazol-1-yl}borate, TpMe,Me, M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5methylpyrazol-1-yl}borate, TpPh,Me, M = Mn, Co, Fe, Ni, n = 1) were prepared and
characterized. These complexes were utilized as metal catalysts for nitrene transfer from
phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in
olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide
range of organic products was obtained and fully characterized, and reaction mechanisms
were probed with Hammett and kinetic isotope effects.
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50
CHAPTER 2: SYNTHESIS AND CHARACTERIZATION OF TRANSITION METAL
SCORPIONATE COMPLEXES
Introduction
The family of hydrotris(pyrazolyl)borates (Tp) have been extensively employed
in bioinorganic, coordination and organometallic chemistry.1-4 Such versatile ligands
typically adopt κ2 or κ3 coordination modes toward a metal center, thus resembling the
action of a scorpion and therefore are nicknamed “scorpionate” ligands. Certain transition
metal complexes stabilized by Tp ligands were found to catalyze a variety of chemical
reactions, including C-H bond activation reactions, carbene transfer reactions and nitrene
transfer reactions. For instance, activation of aliphatic and aromatic C-H bonds has been
achieved by photolysis of TpMe,MeRh(CO)2, which proceeded with loss of CO.5 Pérez and
co-workers employed [TpBr3Cu(NCMe)] as a catalyst to effect C-H bond amination of
cyclohexane and benzene.6 A variety of TpRCu complexes were found to catalyze the
reaction of carbene precursor ethyl diazoacetate and nitrene precursor PhI=NTs with
olefins to form cyclopropanes and aziridines, respectively.7-10 Compared with anionic
scorpionate ligands Tp, the chemistry of metal complexes supported by the neutral
analogous tris(pyrazolyl)methanes (Tpm) remains underdeveloped.
Isoelectronic
TpmM2+ and TpM+ Lewis acid centers should show varying catalytic activities. The
greater positive charge on the metal center in the Tpm cases should cause TpmM2+ to be
more electrophilic than its less positively charged TpM+ analogue. Therefore, the
TpmM2+ fragment should exhibit greater catalytic reactivity toward nitrogen atom
transfer reactions. Pérez and co-workers reported the nitrene transfer ability of
51
[TpmRCu(NCMe)]BF4 in ionic liquid.11 On the other hand, despite Cu(I) complexes
supported by scorpionate ligands (TpR and TpmR) having been successfully employed as
catalysts in nitrene transfer reactions, the later first-row transition metal (Mn, Fe, Co, Ni)
analogs have not been investigated. In this present work, we describe the preparation and
characterization
of
labile
MeCN-coordinated
transition
metal
complexes,
[(L)M(NCMe)3](BF4)n (1M, L = tris{3,5-dimethylpyrazol-1-yl}methane, TpmMe,Me, M =
Mn, Fe, Co, Ni, n = 2; 2M, L = tris{3-phenylpyrazol-1-yl}methane, TpmPh, M = Mn, Fe,
Co, Ni, n = 2; 3M, L = hydrotris{3,5-dimethylpyrazol-1-yl}borate, TpMe,Me, M = Fe, Co,
Ni, n = 1; 4M, L = hydrotris{3-phenyl-5-methylpyrazol-1-yl}borate, TpPh,Me, M = Mn, Co,
Fe, Ni, n = 1).12,13 Such transition metal complexes could turn out to be potentially useful
catalysts toward nitrene transfer reactions, partially owing to the lability of the solvento
ligand CH3CN, which can be readily replaced by other nucleophiles.
Experimental Details
General Procedures. All manipulations were carried out under an inert
atmosphere of prepurified argon, either in a glovebox (MBraun Unilab) or using Schlenk
techniques. Tris(3,5-dimethylpyrazol-1-yl)methane (TpmMe,Me), tris(3-phenylpyrazol-1yl)methane (TpmPh) and hydrotris(pyrazol-1-yl)borate thallium complexes TlTpR,Me (R =
Me, Ph) were prepared by local modification of literature procedures (Caution! Thallium
salts are extremely toxic and must be properly handled and disposed of).14-16 Metal salts,
[M(NCMe)n](BF4)2 (M = Mn, n = 4; M = Fe, Co, Ni, n = 6), were prepared by literature
procedures as described below.17 Complexes [(L)M(NCMe)3](BF4)n (1M, L = TpmMe,Me,
M = Mn, Fe, Co, Ni, n = 2; 2M, L = TpmPh, M = Mn, Fe, Co, Ni, n = 2; 3M, L = TpMe,Me,
52
M = Fe, Co, Ni, n = 1; 4M, L = TpPh,Me, M = Mn, Co, Fe, Ni, n = 1) were prepared by
modification of literature procedures from reactions of [M(NCMe)n](BF4)2 and TpmMe,Me,
TpmPh and TlTpR,Me (R = Me, Ph), respectively, in CH3CN/CH2Cl2.12 Manganese metal
chips, iron powder, cobalt powder, and nickel powder were purchased from Aldrich and
used without further purifications. Dichloromethane (CH2Cl2) and acetonitrile (CH3CN)
were degassed and distilled over calcium hydride (CaH2) before use. Diethyl ether (Et2O)
was degassed and distilled over sodium/benzophenone (Na/Ph2CO). Deuterated solvents
chloroform-d and acetonitrile-d3 were vacuum-transferred from CaH2 and degassed by
the freeze-pump-thaw method prior to use. 1H NMR data were recorded on a Varian
Unity 500 spectrometer and processed using the MestReNova software suite (Mestrelab
Research, Santiago de Compostela, Spain); spectra were referenced internally to the
residual CH3CN solvent resonance (1.94 ppm). Solution magnetic moments of
[(L)M(NCMe)3](BF4)n (1M-4M) were determined by the Evans NMR method in CD3CN at
295 K.18 FT-IR spectra were recorded from KBr pellets on a Thermo-Electron Nicolet
380 spectrophotometer. UV–visible-NIR spectra were recorded on an Agilent HP-8453
diode-array spectrophotometer; heating and cooling were controlled by a VMR bath.
Elemental analyses were performed by Atlantic Microlabs, Inc. (Norcross, GA); as
previously noted, analytical data for the scorpionate complexes were not successful due
to solvento ligand loss.12,13
Preparation of [M(CH3CN)6](BF4)2 (M = Fe, Co, Ni).17 In general, 1.0 g of
NOBF4 (8.64 mmol) and powdered metal (M= Fe, Co, Ni) (0.59 g, 0.63 g, 0.62 g,
repectively, 10.64 mmol) were loaded into a 500 mL Schlenk flask in a glovebox.
53
Distilled CH3CN (80 mL) was added, and the mixture was stirred at room temperature
and the flask was exposed to vacuum until the solution began to bubble vigorously. The
flask was then backfilled with nitrogen, and this process was repeated three additional
times to remove the liberated NO gas (Caution! NO gas is extremely toxic). The mixture
was allowed to stir at room temperature overnight and was then filtered through a frit.
Solvent was then evaporated under vacuum until the solution became cloudy, then Et2O
(50 mL) was added to complete the precipitation. The mixture was allowed to cool down
in a freezer (-37 ºC) to allow the solid to settle. The solid product was recovered by
filtration, washed with Et2O (20 mL) twice, and thoroughly dried under vacuum. Yields
were 1.40 g (2.94 mmol, 68%) for the white Fe(II) product, 1.72 g (3.59 mmol, 83%) for
the pink Co(II) solid, and 1.83 g (3.82 mmol, 89%) for the blue Ni(II) compound.
Preparation of [Mn(CH3CN)4](BF4)2.17 Manganese metal chips (1.60 g, 29.1
mmol, excess) and NOBF4 (1.64 g, 14.0 mmol) were added to a 500 mL Schlenk flask in
a glovebox. Distilled CH3CN (40 mL) was added with stirring and the NO(g) was
allowed to escape through a needle outlet placed in a septum. After stirring overnight, the
reaction mixture was filtered and the colorless filtrate was concentrated under vacuum to
about 5 mL. Et2O (40 mL) was added and the flask was cooled to -37 ºC to produce a
white precipitate. Solvent was removed and the solid was washed with Et2O (20 mL)
twice and dried under vacuum to yield a white crystalline product. Yield 2.32 g (5.90
mmol, 84%).
Preparation of [TpmMe,MeMn(NCMe)3](BF4)2 (1Mn). To the solution of
[Mn(NCMe)4](BF4)2 (196.4 mg, 0.5 mmol) in CH3CN (20 mL), was added dropwise a
54
solution of TpmMe,Me (149.2 mg, 0.5 mmol) in CH2Cl2 (20 mL) with stirring at room
temperature. The mixture was allowed to stir overnight and solvents were removed under
vacuum to yield a light yellow solid residue. CH3CN (10 mL) was added to dissolve the
solid residue, the solution was allowed to stir for about 10 min, then solvent was removed
and the resulting light yellow solid was dried under vacuum overnight. Colorless
crystalline material was obtained by vapor diffusion of diethyl ether into a concentrated
solution of 1Mn in CH3CN at room temperature. Yield: 291 mg (0.45 mmol, 90%). Anal.
Calc’d. (found) for C22H31B2F8MnN9: C, 40.65 (40.04); H, 4.81 (4.81); N, 19.39 (18.97).
µ eff = 5.90 µ B. FT-IR (KBr, cm-1): 2313, ν (C≡N); 2281, ν (C≡N).
Preparation of [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe).12 The light yellow complex
was prepared as for 1Mn above using [Fe(NCMe)6](BF4)2 (237.9 mg, 0.5 mmol) and
TpmMe,Me (149.2 mg, 0.5 mmol). Yield: 321 mg (0.49 mmol, 98%). 1H NMR (CD3CN,
295 K; δ, ppm): 55.9 (3H, 4-pz); 46.5 (9H, 3-Me); 14.9 (9H, 5-Me); -58.4 (1H, C-H). µ eff
= 5.87 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 863 (6.1). FT-IR (KBr, cm-1):
2313, ν (C≡N); 2283, ν (C≡N).
Preparation of [TpmMe,MeCo(NCMe)3](BF4)2 (1Co).12 The orange complex was
prepared as for 1Mn above using [Co(NCCH3)6](BF4)2 (239.4 mg, 0.5 mmol) and
TpmMe,Me (149.2 mg, 0.5 mmol). Yield: 314 mg (0.48 mmol, 96%). 1H NMR (CD3CN,
295 K; δ, ppm): 106.5 (1H, C-H); 55.8 (3H, 4-pz); 44.0 (9H, 5-Me); -70.2 (9H, 3-Me).
µ eff = 4.99 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 467 (32.6), 516 (16.1, sh), 972
(2.8). FT-IR (KBr, cm-1): 2314, ν (C≡N); 2287, ν (C≡N).
55
Preparation of [TpmMe,MeNi(NCMe)3](BF4)2 (1Ni). The blue-purple complex was
prepared as for 1Mn above using [Ni(NCMe)6](BF4)2 (239.3 mg, 0.5 mmol) and TpmMe,Me
(149.2 mg, 0.5 mmol). Yield: 318 mg (0.486 mmol, 97%). 1H NMR (CD3CN, 295 K; δ,
ppm): 58.5 (3H, 4-pz); -3.0 (9H, 5-Me); -9.0 (10H, 3-Me + C-H). µ eff = 3.14 µ B. UV-Vis
(CH3CN, λmax, nm; ε, mM-1 cm-1): 581 (16.6), 743 (3.1), 925 (5.5). FT-IR (KBr, cm-1):
2319, ν (C≡N); 2291, ν (C≡N).
Preparation of [TpmPhMn(NCMe)3](BF4)2 (2Mn). The light yellow complex was
prepared as for 1Mn above using [Mn(NCMe)4](BF4)2 (196.4 mg, 0.5 mmol) and TpmPh
(221.3 mg, 0.5 mmol). Yield: 315 mg (0.397 mmol, 79%). Anal. Calc’d. (found) for
C34H31B2F8MnN9: C, 51.42 (50.55); H, 3.93 (3.88); N, 15.87 (15.51). µ eff = 5.94 µ B. FTIR (KBr, cm-1): 2308, ν (C≡N); 2280, ν (C≡N).
Preparation of [TpmPhFe(NCMe)3](BF4)2 (2Fe).12 The light yellow complex was
prepared as for 1Mn above using [Fe(NCMe)6](BF4)2 (237.9 mg, 0.5 mmol) and TpmPh
(221.3 mg, 0.5 mmol). Yield: 390 mg (0.49 mmol, 98%). 1H NMR (CD3CN, 295 K; δ,
ppm): 47.6 (3H, 4-pz); 27.4 (6H, 3-o-Ph); 12.8 (6H, 3-m-Ph); 5.9 (3H, 3-p-Ph); -4.5 (3H,
5-pz); -53.4 (1H, C-H). µ eff = 5.75 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 905
(10.6). FT-IR (KBr, cm-1): 2308, ν (C≡N); 2282, ν (C≡N).
Preparation of [TpmPhCo(NCMe)3](BF4)2 (2Co).12 The orange complex was
prepared as for 1Mn using [Co(NCMe)6](BF4)2 (239.4 mg, 0.5 mmol) and TpmPh (221.3
mg, 0.5 mmol). Yield: 387 mg (0.485 mmol, 97%). 1H NMR (CD3CN, 295 K; δ, ppm):
110.8 (1H, C-H); 75.3 (3H, 5-pz); 47.3 (3H, 4-pz); -4.4 (9H, 3-m-Ph + 3-p-Ph); -57.3
56
(6H, 3-o-Ph). µ eff = 4.96 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 470 (40.9), 512
(31.4, sh), 992 (2.8). FT-IR (KBr, cm-1): 2315, ν (C≡N); 2290, ν (C≡N).
Preparation of [TpmPhNi(NCMe)3](BF4)2 (2Ni). The blue-purple complex was
prepared as for 1Mn above using [Ni(NCMe)6](BF4)2 (239.3 mg, 0.5 mmol) and TpmPh
(221.3 mg, 0.5 mmol). Yield: 356 mg (0.445 mmol, 89%). Anal. Calc’d. (found) for
C34H31B2F8NiN9: C, 51.18 (50.32); H, 3.92 (4.01); N, 15.80 (16.18). 1H NMR (CD3CN,
295 K; δ, ppm): 49.6 (3H, 4-pz); 40.2 (3H, 5-pz); 7.9 (6H, 3-o-Ph); 7.5 (6H, 3-m-Ph); 6.9
(3H, 3-p-Ph); -7.3 (1H, C-H). µ eff = 3.01 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1):
588 (24.4), 972 (5.9). FT-IR (KBr, cm-1): 2318, ν (C≡N); 2290, ν (C≡N).
Preparation
of
[TpMe,MeFe(NCMe)3]BF4
(3Fe).
To
the
solution
of
[Fe(NCMe)6](BF4)2 (237.9 mg, 0.5 mmol) in CH3CN (20 mL), was added dropwise a
solution of TlTpMe,Me (250.8 mg, 0.5 mmol) in CH2Cl2 (20 mL) with stirring at room
temperature. The mixture was allowed to stir overnight, and then solvents were removed
under vacuum. The resulting orange solid was extracted into CH2Cl2 (20 mL). The
extracts were then filtered and evaporated to yield an orange solid. After drying the solid
for 2 hours, 10 mL CH3CN was added to dissolve the solid. Then the resulting orange
solution was stirred for 10 min and solvents were removed under vacuum to yield an
orange solid. Light orange crystals were obtained by vapor diffusion of diethyl ether into
concentrated CH3CN solution of 3Fe at room temperature. Yield: 196 mg (0.35 mmol,
70%). 1H NMR (CD3CN, 295 K; δ, ppm): 57.3 (3H, 4-pz); 48.4 (9H, 3-Me); 16.8 (9H, 5Me); -60.6 (1H, B-H). µ eff = 5.62 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 478
(93.0), 830 (9.5). FT-IR (KBr, cm-1): 2540, ν (B-H); 2311, ν (C≡N); 2278, ν (C≡N).
57
Preparation of [TpMe,MeCo(NCMe)3]BF4 (3Co). The orange complex was prepared
as for 3Fe above using [Co(NCMe)6](BF4)2 (239.4 mg, 0.5 mmol) and TlTpMe,Me (250.8
mg, 0.5 mmol). The orange complex turned purple after drying under vacuum. Yield: 184
mg (0.325 mmol, 65%). 1H NMR (CD3CN, 295 K; δ, ppm): 77.9 (1H, B-H); 56.9 (3H, 4pz); 39.5 (9H, 5-Me); -56.1 (9H, 3-Me). µ eff = 4.80 µ B. UV-Vis (CH3CN, λmax, nm; ε,
mM-1 cm-1): 483 (45.7), 503 (45.4, sh), 527 (46.9, sh), 581 (40.3), 621 (29.6, sh), 1021
(10.8). FT-IR (KBr, cm-1): 2526, ν (B-H); 2303, ν (C≡N); 2277, ν (C≡N).
Preparation of [TpMe,MeNi(NCMe)3]BF4 (3Ni). The blue complex was prepared as
for 3Fe above using [Ni(NCMe)6](BF4)2 (239.3 mg, 0.5 mmol) and TlTpMe,Me (250.8 mg,
0.5 mmol). The blue complex turned green after drying under vacuum. Yield: 175 mg
(0.31 mmol, 62%). 1H NMR (CD3CN, 295 K; δ, ppm): 63.2 (3H, 4-pz); -2.3 (9H, 5-Me);
-7.7 (9H, 3-Me); -12.0 (1H, B-H). µ eff = 2.81 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm1
): 375 (30.0), 597 (21.3), 757 (4.0), 943 (10.6). FT-IR (KBr, cm-1): 2523, ν (B-H); 2323,
ν (C≡N); 2298, ν (C≡N).
Preparation of [TpPh,MeMn(NCMe)3]BF4 (4Mn). The colorless complex was
prepared as for 3Fe above using [Mn(NCMe)4](BF4)2 (196.4 mg, 0.5 mmol) and TlTpPh,Me
(343.9 mg, 0.5 mmol). Yield: 286 mg (0.38 mmol, 76%). µ eff = 5.90 µ B. FT-IR (KBr, cm1
): 2550, ν (B-H); 2308, ν (C≡N); 2280, ν (C≡N).
Preparation of [TpPh,MeFe(NCMe)3]BF4 (4Fe). The colorless complex was
prepared as for 3Fe above using [Fe(NCMe)6](BF4)2 (237.9 mg, 0.5 mmol) and TlTpPh,Me
(343.9 mg, 0.5 mmol). Yield: 323 mg (0.43 mmol, 86%). Anal. Calc’d. (found) for
C32H31B2F4FeN7 [4Fe·(-CH3CN)2]: C, 57.61 (56.12); H, 4.68 (4.94); N, 14.70 (14.40). 1H
58
NMR (CD3CN, 295 K; δ, ppm): 55.4 (3H, 4-pz); 29.6 (6H, 3-o-Ph); 21.1 (9H, 5-Me);
10.9 (6H, 3-m-Ph); 6.8 (3H, 3-p-Ph); -56.3 (1H, B-H). µ eff = 5.27 µ B. UV-Vis (CH3CN,
λmax, nm; ε, mM-1 cm-1): 839 (5.4). FT-IR (KBr, cm-1): 2548, ν (B-H); 2310, ν (C≡N);
2281, ν (C≡N).
Preparation of [TpPh,MeCo(NCMe)3]BF4 (4Co).13 The orange complex was
prepared as for 3Fe above using [Co(NCMe)6](BF4)2 (239.4 mg, 0.5 mmol) and TlTpPh,Me
(343.9 mg, 0.5 mmol). The orange complex turned dark purple after drying under
vacuum. Yield: 300 mg (0.4 mmol, 80%). 1H NMR (CD3CN, 295 K; δ, ppm): 69.5 (1H,
B-H); 57.1 (3H, 4-pz); 42.1 (9H, 5-Me); 5.2 (3H, 3-p-Ph); 2.7 (6H, 3-m-Ph); -37.3 (6H,
3-o-Ph). µ eff = 4.82 µ B. UV-Vis (CH3CN, λmax, nm; ε, mM-1 cm-1): 468 (38.4), 519 (48.4),
551 (42.5), 989 (6.7). FT-IR (KBr, cm-1): 2547, ν (B-H); 2314, ν (C≡N); 2287, ν (C≡N).
Preparation of [TpPh,MeNi(NCMe)3]BF4 (4Ni).13 The blue complex was prepared as
for 3Fe above using [Ni(NCMe)6](BF4)2 (239.3 mg, 0.5 mmol) and TlTpPh,Me (343.9 mg,
0.5 mmol). The blue complex turned green after drying under vacuum. Yield: 240 mg
(0.32 mmol, 64%). 1H NMR (CD3CN, 295 K; δ, ppm): 63.8 (3H, 4-pz); 8.0 (6H, 3-o-Ph);
7.0 (9H, 3-m-Ph + 3-p-Ph); 1.6 (9H, 5-Me); -10.8 (1H, B-H). µ eff = 2.94 µ B. UV-Vis
(CH3CN, λmax, nm; ε, mM-1 cm-1): 605 (21.5), 757 (6.1), 839 (8.1). FT-IR (KBr, cm-1):
2546, ν (B-H); 2316, ν (C≡N); 2290, ν (C≡N).
Preparation of [(TpMe,Me)2Mn].19 The preparation of the half-sandwich complex
[TpMe,MeMn(NCMe)3]BF4 was unsuccessful, instead, a bis-ligand sandwich complex
[(TpMe,Me)2Mn] was obtained by using [Mn(NCMe)4](BF4)2 (196.4 mg, 0.5 mmol) and
59
TlTpMe,Me (250.8 mg, 0.5 mmol). Yield: 139 mg (0.22 mmol, 88%). Anal. Calc’d. (found)
for C30H44B2MnN12: C, 55.49 (55.56); H, 6.83 (6.78); N, 25.89 (26.05).
X-ray
Crystallographic
[TpmPhMn(NCMe)3](BF4)2
(2Mn),
Analyses.
Diffraction-quality
[TpmPhNi(NCMe)3](BF4)2•NCMe
crystals
of
(2Ni•NCMe),
[TpMe,MeFe(NCMe)3](BF4)•½NCMe (3Fe•½NCMe), [TpMe,MeCo(NCMe)3](BF4)•½NCMe
(3Co•½NCMe) and [TpPh,MeFe(NCMe)3](BF4)•½NCMe (4Fe•½NCMe) were grown by
vapor diffusion of diethyl ether into concentrated CH3CN solutions. X-ray structural
determinations were performed by Prof. Jeffrey L. Petersen at West Virginia University.
Crystals of appropriate size were washed with perfluoropolyether PFO-XR75 and sealed
under nitrogen in a glass capillary. Each sample was optically aligned on the four-circle
of a Siemens P4 diffractometer equipped with a graphite monochromator, a monocap
collimator, a Mo Kα radiation source (λ = 0.71073 Å), and a SMART CCD detector. The
program SMART (version 5.6)20 was used for diffractometer control, frame scans,
indexing, orientation matrix calculations, least-squares refinement of cell parameters, and
the data collection. All crystallographic raw data frames were read by the program
SAINT (version 5/6.0) and integrated using 3D profiling algorithms. A semi-empirical
absorption correction was applied using the SADABS routine available in SAINT.20 The
data were corrected for Lorentz and polarization effects. Data preparation was carried out
by using the program XPREP.20 The structures were solved by a combination of the
Patterson heavy atom method and difference Fourier analysis with the use of SHELXTL
6.1.21 Idealized positions for the hydrogen atoms were included as fixed contributions
using a riding model with isotropic temperature factors set at 1.2 (B-H, methine and
60
aromatic hydrogens) or 1.5 (methyl hydrogens) times that of the adjacent carbon atom.
The positions of the methyl hydrogen atoms were optimized by a rigid rotating group
refinement with idealized angles. Both anions in the structure of 2Mn exhibited two-site
disorder (ca. 0.43:0.57 and 0.27:0.73) involving ca. 60° rotation about one B-F bond. The
B-F bonds and the interatomic F···F separations were constrained to 1.35 ± 0.01 and 2.20
± 0.01 Å, respectively and the anisotropic ellipsoids for the F atoms were refined using
the ISOR option. One anion was similarly disordered in the structure of 2Ni•NCMe, and
the lattice NCMe molecule was poorly resolved. The anion was refined using a two-site
disorder model (ca. 0.81:0.19), with the B-F bonds and the interatomic F···F separations
constrained to 1.35 ± 0.02 and 2.15 ± 0.01 Å, respectively; the F atoms of the major site
were refined anisotropically. 2Ni•NCMe is isomorphous to the previously reported iron
and cobalt analogs. 3Fe•½NCMe and 3Co•½NCMe are isomorphous; in both lattices the
NCMe molecule was disordered over an inversion center and was treated as a diffuse
electron density contribution with the aid of the SQUEEZE routine in the program
PLATON.22 In 4Fe•½NCMe, the anion exhibited two-site disorder (ca. 0.55:0.45), and the
lattice NCMe molecule was disordered over an inversion center. The B-F bonds,
interatomic F···F separations, C≡N and C-C bonds were constrained to 1.35, 2.10, 1.10
and 1.45 ± 0.01 Å, respectively. The linear absorption coefficient, atomic scattering
factors, and anomalous dispersion corrections were calculated from values found in the
International Tables of X-ray Crystallography.23 Tables showing crystal and refinement
data are given in Appendices 31-35; thermal ellipsoid plots are shown in Figures 2.1-2.5;
relevant bond lengths and angles are listed in Tables 2.1-2.5.
61
Results and Discussion
We prepared and characterized a series of scorpionate ligand supported trisacetonitrile complexes [(L)M(NCMe)3](BF4)n (1M, L = TpmMe,Me, M = Mn, Fe, Co, Ni, n
= 2; 2M, L = TpmPh, M = Mn, Fe, Co, Ni, n = 2; 3M, L = TpMe,Me, M = Fe, Co, Ni, n = 1;
4M, L = TpPh,Me, M = Mn, Co, Fe, Ni, n = 1), as potential nitrene transfer reaction
catalysts. [TpmMe,MeM(NCMe)3](BF4)2 (1M) and [TpmPhM(NCMe)3](BF4)2 (2M; M = Mn,
Fe, Co, Ni) complexes were directly prepared by the treatment of the appropriate metal
salts, [MII(NCMe)n](BF4)2 (n = 4, M = Mn; n = 6, M = Fe, Co, Ni), with TpmMe,Me and
TpmPh, respectively, using CH3CN and CH2Cl2 as solvents. [TpMe,MeM(NCMe)3]BF4 (3M;
M = Fe, Co, Ni) and [TpPh,MeM(NCMe)3]BF4 (4M; M = Mn, Fe, Co, Ni) complexes were
prepared by similar procedures using scorpionate thallium complexes, TlTpMe,Me and
TlTpPh,Me, repectively (Scheme 2.1). Formation of thermally stable bis-ligand complexes,
[(TpmR)2M](BF4)2 and [(TpR)2M] was prevented by introducing sterically bulky
substituents on the 3-position of the pyrazole rings. The using of MeCN coordinated
metal salts was also important to limit the formation of bis-ligand complexes. Despite
these precautions, the bis-ligand sandwich complex [(TpMe,Me)2Mn]19 was inevitably
formed instead of [TpMe,MeMn(NCMe)3]BF4. These complexes are so labile as to be
stable only in the presence of excess MeCN. With drying under vacuum, significant color
changes were observed for complexes 3M and 4M (M = Co, Ni). Elemental analyses on
isolated products were consistent with elimination of MeCN equivalents. Meanwhile,
dissolution of complexes 3M and 4M in non-coordinating CH2Cl2 also resulted in partial
solvento ligand loss. Edwards and co-workers previously reported the syntheses of
62
[TpmMe,MeM(NCMe)3](BF4)2 and [TpmPhM(NCMe)3](BF4)2 (1M and 2M; M = Fe, Co),12
while Akita and co-workers reported the preparation of [TpPh,MeM(NCMe)3]OTf (M =
Co, Ni).13 In addition, crystal structures of [MII(NCMe)6]2+ (M = Mn, Fe, Co, Ni)
precursors have been reported previously. 24-27
Scheme 2.1. Synthesis of complexes 1M-4M (M = Mn, Fe, Co, Ni).
63
Characterization of [(L)M(NCMe)3](BF4)n
A. X-ray Crystallography
The solid-state structures of complexes 2Mn, 2Ni, 3Fe, 3Co and 4Fe were determined
by X-ray crystallography. Attempts to solve the solid state structures of 1Mn and 1Ni failed
due to structural disorder of the BF4- counteranion. Crystallographic data collections of
3Ni and 4Mn were also unsuccessful due to loss of lattice solvent. Thermal ellipsoid plots
of the cationic parts of 2Mn, 2Ni, 3Fe, 3Co and 4Fe are shown in Figures 2.1-2.5. Selected
metal to nitrogen (M-N) bond distances and angles of 2Mn, 2Ni, 3Fe, 3Co and 4Fe are given
in Tables 2.1-2.5. Structure data of 2Mn, 2Ni, 3Fe, 3Co and 4Fe, as well as reported data of
1M-2M (M = Fe, Co),12 [TpPh,MeM(NCMe)3]OTf (4′M, M = Co, Ni)13 and metal salts
[M(NCCH3)6]2+ (M = Mn, Fe, Co, Ni)24-27 are summarized and compared in Tables 2.62.7 and Figure 2.6.
All complexes show similar core structure with ideal C3v symmetry: the metal
center is sandwiched by a scorpionate ligand in a κ3-coordination fashion and three
MeCN molecules ligated trans to nitrogen donor atoms of the scorpionate ligands. The
M-N bond lengths are consistent with high spin states (S = 5/2, 2, 3/2, 1, respectively, for
Mn, Fe, Co, Ni). The average M-Npz and M-NNCMe bond lengths decrease in the order
Mn > Fe > Co > Ni, consistent with their ionic radius. The M-Npz bond lengths are
significantly correlated with the sterics of the 3-pz substituents: scorpionates bearing
phenyl substituents induce longer M-N(pz) bond distances, in the order TpmPh > TpPh,Me
> TpmMe,Me > TpMe,Me. However, the ligand charge has a greater effect on M-NNCMe bond
distances than the sterics: the M-NNCMe bond distances of neutral scorpionate supported
64
complexes are shorter than those of complexes supported by anionic scorpionate ligands,
in the order TpmPh < TpmMe,Me < TpPh,Me < TpMe,Me (Figure 2.6).
As indicated in Table 2.6, the Npz-M-Npz angles of the neutral scorpionate
supported complexes are constrained to a range of 81.0-85.9º by the bite of the TpmMe,Me
and TpmPh chelate, while the Npz-M-Npz angles, constrained by the bite of anionic
scorpionates TpMe,Me and TpPh,Me, fall in a range of 87.6-88.5º. The C/B-N-N-M torsion
angles are significantly correlated with the sterics of the 3-pz substituent: for TpmMe,Me
supported complexes 1Fe and 1Co, the torsion angles average 11.62 and 9.86º,
respectively, while the torsion angles increase to -14.14 and -13.19º in the corresponding
TpmPh supported complexes 3Fe and 3Co, respectively. The size of the metal center also
affects C/B-N-N-M torsion angles as by comparing 1Fe and 1Co. On the other hand, with
the same 3-pz substituents (TpmMe,Me vs TpMe,Me; TpmPh vs TpPh,Me), the C···M nonbonded distances of neutral scorpionate complexes are longer than the B···M non-bonded
distances of the anionic scorpionate complexes, while with the same ligand, the C/B···M
distances decrease as the size of the metal ion decreases, in the order of Mn > Fe > Co >
Ni, as seen in the TpmPh supported complexes 2M. Overall, the increases of both C/B-NN-M torsion angles and C/B···M distances are important ways to accommodate larger
metal ions.
As indicated in Table 2.6 and Table 2.7, the M-NNCMe bond lengths of
[TpmPhM(NCMe)3](BF4)2 (2M, M = Mn, Fe, Co, Ni), averaging 2.219, 2.151, 2.112 and
2.073 Å, respectively, are comparable to the corresponding M-N bond lengths of metal
salts [M(NCCH3)6]2+ (2.222, 2.160, 2.114 and 2.071 Å, respectively, for Mn, Fe, Co and
65
Ni).24-27 However, the M-Npz bond lengths of 2M, averaging 2.297, 2.200, 2.169 and
2.138 Å, respectively, are all longer than the M-N bond lengths of [M(NCCH3)6]2+. This
indicates that the TpmPh ligand is a weaker ligand than MeCN. This conclusion affected
the catalytic reactivity of 2M, as well as the assignment of 1H NMR spectra of 2M (Figure
2.17), since the ligand dissociates from the metal center even in the presence of MeCN.
In addition, the sterics of the 3-pz substituents have a great effect on the
orientation of the MeCN ligands. The comparison of TpMe,Me-supported complex 3Fe with
TpPh,Me-supported complex 4Fe is depicted in Figure 2.7: the MeCN ligands of 3Fe are
bending toward the TpMe,Me ligand, with the Fe-N≡C angles averaging 166.5º; while with
TpPh,Me as the supporting ligand, the MeCN ligands of 4Fe are bending away from the
TpPh,Me ligand, and the Fe-N≡C angles average 176.0º, which is 17.5º smaller than that of
3Fe. Meanwhile, as depicted in Figure 2.7, the sterics of the 3-pz substituents (methyl vs
phenyl) of 3Fe and 4Fe force a rotation of the tris-acetonitrile tripod.
66
Figure 2.1. Thermal ellipsoid plot of the cationic part of 2Mn (30% probability). Hydrogen
atoms are omitted for clarity.
Table 2.1. Selected bond distances (Å) and angles (deg) of 2Mn.
[TpmPhMn(NCMe)3](BF4)2 (2Mn)
d(Mn–Npz), Å
Mn(1)-N(1)
2.307(2)
d(Mn–NNCMe) , Å
Mn(1)-N(7)
2.209(2)
Mn(1)-N(3)
2.292(2)
Mn(1)-N(8)
2.217(2)
Mn(1)-N(5)
2.291(2)
Mn(1)-N(9)
2.231(2)
∠Npz–Mn–Npz, deg
∠NNCMe–Mn–NNCMe, deg
N(5)-Mn(1)-N(1)
81.90(6)
N(7)-Mn(1)-N(8)
90.27(7)
N(3)-Mn(1)-N(1)
80.77(6)
N(7)-Mn(1)-N(9)
86.01(8)
N(5)-Mn(1)-N(3)
80.32(6)
N(8)-Mn(1)-N(9)
85.88(8)
∠Npz–Mn–NNCMe (cis), deg
∠Npz–Mn–NNCMe (trans), deg
N(8)-Mn(1)-N(1)
88.65(7)
N(7)-Mn(1)-N(1)
172.26(7)
N(9)-Mn(1)-N(1)
101.55(7)
N(8)-Mn(1)-N(3)
168.96(6)
N(7)-Mn(1)-N(3)
100.64(7)
N(9)-Mn(1)-N(5)
172.07(7)
N(9)-Mn(1)-N(3)
93.12(7)
N(7)-Mn(1)-N(5)
90.81(7)
N(8)-Mn(1)-N(5)
101.42(7)
67
Figure 2.2. Thermal ellipsoid plot of the cationic part of 2Ni (30% probability). Hydrogen
atoms are omitted for clarity.
Table 2.2. Selected bond distances (Å) and angles (deg) of 2Ni.
[TpmPhNi(NCMe)3](BF4)2 (2Ni)
d(Ni–Npz) , Å
d(Ni–NNCMe) , Å
Ni(1)-N(1)
2.136(2)
Ni(1)-N(7)
2.063(2)
Ni(1)-N(3)
2.139(2)
Ni(1)-N(9)
2.075(3)
Ni(1)-N(5)
2.139(2)
Ni(1)-N(8)
2.080(2)
∠Npz–Ni–Npz, deg
∠NNCMe–Ni–NNCMe, deg
N(1)-Ni(1)-N(3)
86.06(8)
N(7)-Ni(1)-N(9)
86.49(10)
N(1)-Ni(1)-N(5)
87.05(8)
N(7)-Ni(1)-N(8)
87.21(9)
N(3)-Ni(1)-N(5)
84.72(8)
N(9)-Ni(1)-N(8)
89.78(10)
∠Npz–Ni–NNCMe (cis), deg
∠Npz–Ni–NNCMe (trans), deg
N(8)-Ni(1)-N(1)
87.73(8)
N(7)-Ni(1)-N(1)
173.93(8)
N(9)-Ni(1)-N(1)
96.85(9)
N(9)-Ni(1)-N(5)
172.80(8)
N(7)-Ni(1)-N(3)
99.08(8)
N(8)-Ni(1)-N(3)
173.61(9)
N(9)-Ni(1)-N(3)
89.50(9)
N(7)-Ni(1)-N(5)
90.18(9)
N(8)-Ni(1)-N(5)
96.44(9)
68
Figure 2.3. Thermal ellipsoid plot of the cationic part of 3Fe (30% probability). Hydrogen
atoms are omitted for clarity.
Table 2.3. Selected bond distances (Å) and angles (deg) of 3Fe.
[TpMe,MeFe(NCMe)3](BF4) (3Fe)
d(Fe–Npz), Å
Fe(1)-N(1)
2.1423(14)
d(Fe–NNCMe), Å
Fe(1)-N(3)
2.232(2)
Fe(1)-N(1)#1
2.1423(14)
Fe(1)-N(3)#1
2.232(2)
Fe(1)-N(1)#2
2.1423(14)
Fe(1)-N(3)#2
2.232(2)
∠Npz–Fe–Npz, deg
∠NNCMe–Fe–NNCMe, deg
N(1)#1-Fe(1)-N(1)#2
88.45(5)
N(3)-Fe(1)-N(3)#1
87.96(7)
N(1)#1-Fe(1)-N(1)
88.45(5)
N(3)-Fe(1)-N(3)#2
87.96(7)
N(1)#2-Fe(1)-N(1)
88.45(5)
N(3)#1-Fe(1)-N(3)#2
87.96(7)
∠Npz–Fe–NNCMe (cis), deg
N(1)-Fe(1)-N(3)
91.33(6)
N(1)-Fe(1)-N(3)#1
92.26(6)
∠Npz–Fe–NNCMe (trans), deg
N(1)-Fe(1)-N(3)#2
179.26(6)
69
Figure 2.4. Thermal ellipsoid plot of the cationic part of 3Co (30% probability). Hydrogen
atoms are omitted for clarity.
Table 2.4. Selected bond distances (Å) and angles (deg) of 3Co.
[TpMe,MeCo(NCMe)3](BF4) (3Co)
d(Co–Npz), Å
Co(1)-N(1)
2.116(2)
d(Co–NNCMe), Å
Co(1)-N(3)
2.182(2)
Co(1)-N(1)#1
2.116(2)
Co(1)-N(3)#1
2.182(2)
Co(1)-N(1)#2
2.116(2)
Co(1)-N(3)#2
2.182(2)
∠Npz–Co–Npz, deg
∠NNCMe–Co–NNCMe, deg
N(1)#1-Co(1)-N(1)
88.35(7)
N(3)#2-Co(1)-N(3)#1
87.75(9)
N(1)#1-Co(1)-N(1)#2
88.35(7)
N(3)#2-Co(1)-N(3)
87.75(9)
N(1)-Co(1)-N(1)#2
88.35(7)
N(3)#1-Co(1)-N(3)
87.75(9)
∠Npz–Co–NNCMe (cis), deg
N(1)-Co(1)-N(3)
92.55(8)
N(1)-Co(1)-N(3)#2
91.37(8)
∠Npz–Co–NNCMe (trans), deg
N(1)-Co(1)-N(3)#1
179.05(8)
70
Figure 2.5. Thermal ellipsoid plot of the cationic part of 4Fe (30% probability). Hydrogen
atoms are omitted for clarity.
Table 2.5. Selected bond distances (Å) and angles (deg) of 4Fe.
[TpPh,MeFe(NCMe)3](BF4) (4Fe)
d(Fe–Npz), Å
Fe(1)-N(1)
2.150(2)
d(Fe–NNCMe) ), Å
Fe(1)-N(7)
2.204(2)
Fe(1)-N(3)
2.194(2)
Fe(1)-N(8)
2.190(2)
Fe(1)-N(5)
2.190(2)
Fe(1)-N(9)
2.202(2)
∠Npz–Fe–Npz, deg
∠NNCMe–Fe–NNCMe, deg
N(1)-Fe(1)-N(3)
88.50(7)
N(8)-Fe(1)-N(9)
87.48(7)
N(1)-Fe(1)-N(5)
85.57(6)
N(8)-Fe(1)-N(7)
83.13(8)
N(5)-Fe(1)-N(3)
90.32(6)
N(9)-Fe(1)-N(7)
88.29(7)
∠Npz–Fe–NNCMe (cis), deg
∠Npz–Fe–NNCMe (trans), deg
N(1)-Fe(1)-N(8)
91.31(7)
N(1)-Fe(1)-N(7)
171.55(7)
N(1)-Fe(1)-N(9)
97.85(7)
N(3)-Fe(1)-N(8)
176.24(6)
N(3)-Fe(1)-N(7)
97.46(8)
N(5)-Fe(1)-N(9)
176.46(7)
N(3)-Fe(1)-N(9)
88.83(7)
N(5)-Fe(1)-N(7)
88.41(7)
N(5)-Fe(1)-N(8)
93.41(7)
71
Table 2.6. Selected average bond distances (Å) and angles (deg) for tris-acetonitrile complexes.
Compound d(M–Npz), Å d(M–NNCMe), Å d(C/B···M), Å ∠Npz–M–Npz, deg
∠C/B-N–N–M
(torsion, deg)
∠M–N≡C, deg
Ref.
1Fe
2.165
2.165
3.132
84.9
11.62
168.8
12
1Co
2.125
2.122
3.117
85.4
9.86
170.8
12
2Mn
2.297
2.219
3.261
81.0
5.42
165.3
2Fe
2.200
2.151
3.143
84.5
-14.14
171.0
12
2Co
2.169
2.112
3.127
84.9
-13.19
171.8
12
2Ni
2.138
2.073
3.088
85.9
12.78
171.5
3Fe
2.142
2.232
3.125
88.5
-9.27
166.5
3Co
2.116
2.182
3.120
88.4
-8.82
167.2
4Fe
2.178
2.199
3.131
88.1
-18.13
176.0
4′Co
2.150
2.149
3.137
87.6
-17.22
166.8
13
4′Ni
2.110
2.105
3.107
88.5
17.37
166.2
13
Table 2.7. Average M-N bond distances (Å) of metal salts [M(NCCH3)6]2+.24-27
Compound
d(M–N), Å
[Mn(NCCH3)6]2+
[Fe(NCCH3)6]2+
[Co(NCCH3)6]2+
[Ni(NCCH3)6]2+
2.222
2.160
2.114
2.071
72
Figure 2.6. Effectss of scorpionate ligands on metal to nitrogen bond
ond lengths.
73
Figure 2.7. Molecular structures of cationic parts of 3Fe (left) and 4Fe (right) and a spacefilling overlay plot of 3Fe and 4Fe (center), emphasizing the steric effects of 3-pyrazole
substituents (Me vs. Ph) on the rotation of the MeCN ligands.
Table 2.8. Fe-N≡C angles (deg) of complexes [TpMe,MeFe(NCMe)3]BF4 (3Fe) and
[TpPh,MeFe(NCMe)3]BF4 (4Fe).
∠Fe-N≡C of 3Fe and 4Fe
3Fe
4Fe
Fe(1)-N(3)-C(6)
166.53(2)
Fe(1)-N(7)-C(31)
176.27(2)
Fe(1)-N(3)-C(6)
166.53(2)
Fe(1)-N(8)-C(33)
176.11(2)
Fe(1)-N(3)-C(6)
166.53(2)
Fe(1)-N(8)-C(35)
175.51(2)
166.5
Average
Average
bending toward Tp
Me,Me
ligand
bending away from Tp
176.0
Ph,Me
ligand
74
B. Electronic Spectroscopy
Strictly speaking, d-d ligand field transitions are forbidden for centrosymmetric
(octahedral) complexes (Laporte selection rule), but relatively weak absorption of
octahedral complexes can occur due to structural distortions and reduction of symmetry.28
Thus, electronic spectra of complexes 1M-4M (except 3Mn; M = Mn, Fe, Co, Ni) were
investigated by UV-Vis spectroscopy. Electronic absorption data are summarized in
detail in Tables 2.9-2.11. The UV-Vis spectra of C3v symmetric complexes 1M-4M
exhibited electronic absorptions consistent with divalent transition metal ions in ideal
octahedral ligand field environments. The electronic absorptions are comparable to those
of the reported metal salts [MII(NCMe)n](BF4)2 (M = Mn, Fe, Co, Ni) (Table 2.17).
Manganese(II) complexes. According to the d5 Tanabe-Sugano diagram, there are
no spin allowed d-d transitions for high spin Mn(II).28 Moreover, when a high spin
Mn(II) center is coordinated by an organic ligand, it is rarely possible to identify the
weak spin-forbidden d-d transition bands of such a complex, since even the weak UV
organic absorption tailing into the visible could obscure them.28 This effect is seen in
featureless spectra of the Mn(II) complexes 1Mn, 2Mn and 4Mn (Figure 2.8), compared with
[Mn(NCMe)4](BF4)2 (Table 2.17).17
Iron(II) complexes. According to the d6 Tanabe-Sugano diagram, a single spinallowed (5Eg ← 5T2g) d-d transition is allowed for high spin Fe(II). The UV-Vis-NIR
spectra of the Fe(II) complexes (1Fe-4Fe) exhibit such a band in the range at 839 – 905 nm
(ε = 3.4 – 10.6 M-1 cm-1), see Figure 2.9 and Table 2.9. Additional bands were observed
in the visible range at 478 nm (ε = 93.0 M-1 cm-1) and 580 nm (shoulder, ε = 18.1 M-1 cm-
75
1
) for the TpMe,Me-supported complex 3Fe. The relatively small extinction coefficient of
the absorption band at 580 nm indicates that it is a d-d transition, while the relatively
strong band at 478 is assigned to a Fe → NCCH3 MLCT. Solutions of high spin d6 Fe(II)
compounds are commonly colorless, while the MeCN solution of 3Fe shows a visibly
orange color. Therefore, based on the precedent studies of TpmR supported sandwich
octahedral Fe(II) complexes possessing spin-state crossover,29-31 we propose that this
band indicates the presence of low-spin 3Fe in MeCN solution, assigned to the spinallowed 1T1g ← 1A1g transition (Table 2.9).31 However, there is no evidence of spin
crossover in the solid state of 3Fe, since the Fe-Npz bond lengths of 3Fe average to 2.14 Å
(Table 2.6), consistent with a high spin configuration of the octahedral Fe center, while
the typical Fe-N bond distance for low spin octahedral FeN6 complexes is 1.97 Å.32
In order to further elucidate the spin equilibrium of 3Fe, the absorption bands of
3Fe in acetonitrile solution were monitored by UV-Vis spectroscopy at a variety of
temperatures. A moderate bleaching of the absorption band at 478 nm was observed as
the solution temperature was increased from 20-60 ºC (Figure 2.10). This appeared to be
reversible as cooling down the solution to room temperature gave an absorption band
with similar intensity as the measured before heating. This experiment shows an
unambiguous onset of the spin crossover in solution; the conversion from high spin to
low spin is incomplete at this temperature range.
76
Figure 2.8. UV-Vis spectra of Mn(II) complexes 1Mn (solid gray line), 2Mn (dashed gray
line) and 4Mn (dashed black line) recorded in CH3CN at 295 K.
77
Figure 2.9. UV-Vis spectra (CH3CN, 295 K) of Fe(II) complexes 1Fe (solid gray line), 2Fe
(dashed gray line), 3Fe (solid black line) and 4Fe (dashed black line).
Table 2.9. UV-Vis spectra data for Fe(II) complexes 1Fe-4Fe .
Complex
λ, nm
ε, M-1 cm-1 Comment
Assignment
[TpmMe,MeFe(CH3CN)3](BF4)2
863
6.1
5
Eg ← 5T2g
[TpmPhFe(CH3CN)3](BF4)2
905
10.6
5
Eg ← 5T2g
[TpMe,MeFe(CH3CN)3]BF4
830
9.5
5
Eg ← 5T2g
580
18.1
478
93.0
[Tp
Ph,Me
Fe(CH3CN)3]BF4
839
5.4
low spin
1
T1g ← 1A1g
MLCT
5
Eg ← 5T2g
78
Figure 2.10. UV-Vis spectra of 3Fe [TpMe,MeFe(NCMe)3]BF4 in CH3CN showing the onset
of spin crossover behavior.
79
Cobalt(II) complexes. Typically, the Tanabe-Sugano diagram indicates three spin
allowed d-d transitions for high spin d7 Co(II), namely 4T2g(F) ← 4T1g(F), 4A2g ← 4T1g(F)
and 4T1g(P) ← 4T1g(F).28 The Co(II) complexes (1Co-4Co) exhibit a low energy transition
in the near IR, 4T2g(F) ← 4T1g(F), ranging from 970 – 1020 nm (ε = 2.8 – 10.8 M-1 cm-1)
(Figure 2.11, Table 2.10). In addition, for each of these four Co(II) complexes, an
asymmetric band with distinct multiple splitting is observed in the visible region (λmax =
467 – 483 nm; ε = 32.6 – 45.7 M-1 cm-1). The asymmetric structure of this absorption
band in the visible region is typical for octahedral Co(II) complexes and cannot be easily
assigned. The multiple splitting within the absorption band could arise both from trigonal
ligand field distortion (Oh → C3v), as well as appearance of doublet states (2T1g, 2T2g) via
spin-orbit coupling. In addition, the 4A2g and 4T1g(P) excited states are usually close in
energy, making the band assignment of high spin Co(II) complexes rather difficult.28,33-35
The UV-Vis spectrum of [TpMe,MeCo(NCMe)3]BF4 (3Co) is shown in Figure 2.12.
Compared with spectra of the other three Co(II) complexes, 3Co shows more splitting.
This may be due to the exceptional trigonal distortion of 3Co indicated by comparison of
the average Co–Npz and Co–NNCMe bond distances (Table 2.6).
Nickel(II) complexes. The UV-Vis spectra of tris-acetonitrile Ni(II) complexes
(1Ni-4Ni) showed spectral features consistent with octahedral coordination of d8 Ni(II) ion
(Figure 2.13).28,35-37 The listing of major bands and assignments are given in detail in
Table 2.11. The four Ni(II) complexes (1Ni-4Ni) all exhibited weak, single absorption
bands at 839 – 972 nm (ε = 5.5 – 10.6 M-1 cm-1) and at 581 – 605 nm (ε = 16.6 – 24.4 M-1
cm-1). They were respectively assigned to the spin allowed 3T2g(F) ← 3A2g and 3T1g(F) ←
80
3
A2g transitions under parent Oh symmetry, by comparison to [Ni(NCMe)6](BF4)2 (Table
2.17).17 Relatively weak peaks at 743 – 757 nm (ε = 3.1 – 6.1 M-1 cm-1) were observed
for these Ni(II) complexes except for compound 2Ni, [TpmPhNi(NCMe)3](BF4)2. These
weak shoulder absorption bands can be assigned to the spin forbidden 1Eg ← 3A2g
transition.37 A high-energy absorption band of complex 3Ni at 375 nm (ε = 30.0 M-1 cm-1)
is assigned to the spin allowed 3T1g(P) ← 3A2g transition (Figure 2.14); this high-energy
absorption is usually obscured by UV tailing, as seen for tris-acetonitrile Ni(II)
complexes 1Ni, 2Ni and 4Ni (Figure 2.13).
81
Figure 2.11. UV-Vis spectra (CH3CN, 295 K) of Co(II) complexes 1Co (solid gray line),
2Co (dashed gray line), 3Co (solid black line) and 4Co (dashed black line).
Figure 2.12. UV-Vis spectrum (CH3CN, 295 K) of 3Co [TpMe,MeCo(NCMe)3]BF4.
82
Table 2.10. UV-Vis spectra data for Co(II) complexes 1Co-4Co .
Complex
[TpmMe,MeCo(CH3CN)3](BF4)2
[TpmPhCo(CH3CN)3](BF4)2
[TpMe,MeCo(CH3CN)3]BF4
[TpPh,MeCo(CH3CN)3]BF4
λ, nm
ε, M-1 cm-1
972
2.8
516 (sh)
16.1
467
32.6
992
2.8
512 (sh)
31.4
470
40.9
1021
10.8
621 (sh)
29.6
581
40.3
527
46.9
503 (sh)
45.4
483
45.7
989
6.7
551 (sh)
42.5
519
48.4
468
38.4
Assignment
4
T2g(F) ← 4T1g(F)
4
T2g(F) ← 4T1g(F)
4
T2g(F) ← 4T1g(F)
4
T2g(F) ← 4T1g(F)
83
Figure 2.13. UV-Vis spectra (CH3CN, 295 K) of Ni(II) complexes 1Ni (solid gray line),
2Ni (dashed gray line), 3Ni (solid black line) and 4Ni (dashed black line).
Figure 2.14. UV-Vis spectrum of 3Ni [TpMe,MeNi(NCMe)3]BF4 recorded in CH3CN at 295
K showing the absorption band assignments.
84
Table 2.11. UV-Vis spectra data for Ni(II) complexes 1Ni-4Ni.
Complex
[TpmMe,MeNi(CH3CN)3](BF4)2
λ, nm
ε, M-1 cm-1 Comment
925
5.5
743
3.1
581
16.6
3
972
5.9
588
24.4
[TpPh,MeNi(CH3CN)3](BF4)
Eg ← 3A2g
3
T1g(F) ← 3A2g
3
T1g(P) ← 3A2g
3
T2g(F) ← 3A2g
3
obscured
[TpMe,MeNi(CH3CN)3](BF4)
T2g(F) ← 3A2g
1
obscured
[TpmPhNi(CH3CN)3](BF4)2
Assignment
T1g(F) ← 3A2g
3
T1g(P) ← 3A2g
3
T2g(F) ← 3A2g
943
10.6
757
4.0
597
21.3
3
T1g(F) ← 3A2g
375
30.0
3
T1g(P) ← 3A2g
839
8.1
3
T2g(F) ← 3A2g
757
6.1
605
21.5
1
1
obscured
Eg ← 3A2g
Eg ← 3A2g
3
T1g(F) ← 3A2g
3
T1g(P) ← 3A2g
85
C. 1H NMR Spectroscopy
Complexes 1M-4M (M = Fe, Co, Ni) all exhibited broad well-resolved 1H NMR
spectra at room temperature in CD3CN solution, as expected for their paramagnetic high
spin electron configurations (S = 2, 3/2, 1, respectively, for Fe, Co, Ni; Figures 2.152.18).16 Chemical shifts are summarized in detail in Tables 2.12-2.13.
In an octahedral ligand field, the ground state of the Ni(II) complex is an orbitally
nondegenerate 3A2g state. This state would not be expected to give rise to significant
dipolar (through-space) hyperfine shifts.38 The shifts found for Ni(II) complexes 1Ni-4Ni
are dominated by through-bond interaction (contact shift). The C(B)-H, 3-Me (3-Ph) and
5-Me pyrazolyl resonances of complexes 1Ni-4Ni are all close to the diamagnetic region
(5-H pyrazolyl resonance of 3Ni is shifted downfield to 40.2 ppm), while all the 4-H
pyrazolyl resonances are significantly shifted downfield to 58.5, 49.6, 63.2 and 63.8 ppm,
respectively, indicating the spin is delocalized through the π orbital. On the other hand,
the ground states of Fe(II) and Co(II) complexes have holes in t2g orbitals under an
octahedral ligand field; such ground states would give rise to considerable through-space
dipolar shift. Therefore, we consider the shifts in Fe(II) complexes 1Fe-4Fe and Co(II)
complexes 1Co-4Co to arise from both contact shift and dipolar shift (opposite sign for
Fe(II) and Co(II) complexes). The dipolar effect on the shifts of the TpmMe,Me ligand of
1Co and 1Fe will be discussed as examples. Compared with the shift pattern of 1Ni, the CH resonance for 1Co is significantly downfield to 106.5 ppm, the 5-Me resonance is also
downfield to 44.0 ppm, while the 3-Me resonance is shifted upfield to -70.2 ppm.
However, the 4-H pyrazolyl resonance is barely shifted compared with that of 1Ni,
86
resonating at 55.8 ppm. Based on literature precedent, a three-dimensional double-cone
graph can be used to interpret the shift pattern of 1Co (Figure 2.19).38-43 The direction of
the double-cone (z axis of the magnetic field) is along the H-C···Co axis. The 5-Me and
C-H protons are always in the positive section of the double cone, therefore, these
resonances are significantly shifted to downfield area. The 3-Me protons are in the
negative section, shifting the resonance at upfield. On the other hand, the overall dipolar
shifting of 1Fe is reversed, making the C-H proton fall upfield, while the 3-Me and 5-Me
protons fall downfield.39,41
In addition, resonances of free TpmPh ligand protons were observed in the 1H
NMR spectra of the TpmPh-supported complexes 2M (M = Fe, Co, Ni). After carefully
comparing the M-Npz bond lengths of 2M with the M-N bond lengths of the
corresponding metal salts, [M(NCMe)6](BF4)2, we found that the average M-Npz bond
lengths of 2M are longer than the M-N bond lengths of the corresponding metal salts
(Figure 2.6). Therefore, dissociation of the weakly coordinated TpmPh ligand in CD3CN
solution was observed in the 1H NMR spectra of 2M (Figure 2.17).
87
Table 2.12. Chemical shifts for TpmMe,Me and TpMe,Me-supported complexes 1M and 3M
(M = Fe, Co, Ni) recorded in CD3CN at 295 K.
Proton
position
TpmMe,Me (δ, ppm) (1M)
Fe
Co
Ni
TpMe,Me (δ, ppm) (3M)
Fe
Co
Ni
4-H
55.9
55.8
58.5
57.3
56.9
63.2
3-Me
46.5
-70.2
-9.0
48.4
-56.1
-7.7
5-Me
14.9
44.0
-3.0
16.5
39.5
-2.3
C-H
-58.4
106.5
-9.0
–
–
–
B-H
–
–
–
-60.6
77.9
-12.0
Table 2.13. Chemical shifts for TpmPh and TpPh,Me-supported complexes 2M and 4M (M =
Fe, Co, Ni) recorded in CD3CN at 295 K.
Proton
position
TpmPh (δ, ppm) (2M)
Fe
Co
Ni
TpPh,Me (δ, ppm) (4M)
Fe
Co
Ni
4-H
47.6
47.3
49.6
55.4
57.1
63.8
3-Ph, para
5.9
-4.4
6.9
6.8
5.2
7.0
3-Ph, meta
12.8
-4.4
7.5
10.9
2.7
7.0
3-Ph, ortho
27.4
-57.3
7.9
29.6
-37.6
8.0
5-H
-4.5
75.3
40.2
–
–
–
C-H
-53.4
110.8
-7.3
–
–
–
5-Me
–
–
–
21.1
42.1
1.6
B-H
–
–
–
-56.3
69.5
-10.8
88
H
Me
Me
C
5
H
N
4
N
N
N
Me
H
N
H
N
3
Me
Me
M
N
N
Me
Me
N
Me
Me
Figure 2.15. 1H NMR spectra (CD3CN, 295 K) of TpmMe,Me-supported
supported complexes 1Fe, 1Co
and 1Ni. Peaks due to CH3CN are marked “s”; lattice solvents (CH2Cl2) are denoted with
an asterisk (*).
89
H
Me
Me
B
5
H
N
4
N
N
N
Me
H
N
H
N
Me
3
Me
M
N
N
Me
Me
N
Me
Me
Figure 2.16. 1H NMR spectra (CD3CN, 295 K) of TpMe,Me-supported
supported complexes 3Fe, 3Co
and 3Ni. Peaks due to CH3CN are marked “s”; lattice solvents (CH2Cl2) are denoted with
an asterisk (*).
90
H
H
H
C
5
H
H
N
4
N
N
H
H
N
H
Ph
M
N
Ph
N
N
Me
H
H
N
3
H
H
N
Me
Me
Figure 2.17. 1H NMR spectra (CD3CN, 295 K) of TpmPh-supported
supported complexes 2Fe, 2Co
and 2Ni. Peaks due to CH3CN are marked “s”; lattice solvents (CH2Cl2) are denoted with
an asterisk (*); resonances of free TpmPh ligand are denoted as TpmPh.
91
H
Me
Me
B
5
H
H
N
4
N
N
H
H
N
H
Ph
M
N
Ph
N
N
Me
H
Me
N
3
H
H
N
Me
Me
Figure 2.18. 1H NMR spectra (CD3CN, 295 K) of TpPh,Me-supported
supported complexes 4Fe, 4Co
and 4Ni. Peaks due to CH3CN are marked “s”; lattice solvents (CH2Cl2) are denoted with
an asterisk (*).
92
Figure 2.19. Graphical representation of complex 1Co in a dipolar double cone.
93
D. FT-IR Spectroscopy
Complexes 1M-4M (M = Mn, Fe, Co, Ni) were all characterized by infrared
spectroscopy using KBr as a matrix (Figures 2.20-2.23). The results are summarized in
Tables 2.14-2.15. The κ3 coordination fashion of TpR ligands of 3M-4M was confirmed by
the νB-H absorptions in the range of 2523 – 2550 cm-1.16,44 The IR spectra of 1M-4M
display two νCN bands in a range of 2278 – 2298 cm-1 and 2303 – 2323 cm-1, respectively,
with medium intensity. Absorptions in this spectral region are typical for coordinated
MeCN. The two νCN absorptions can be straightforwardly assigned to the fundamental ν2CN stretching mode and the combination mode (ν3 + ν4), similar to the assignment of free
MeCN.45,46 The νCN absorptions are also comparable to those of known metal salts,
[MII(NCMe)n](BF4)2 (n = 4, M = Mn; n = 6, M = Fe, Co, Ni) (Table 2.17).17,46 The
emergence of two absorption bands of MeCN is due to the Fermi resonance between the
ν2-CN fundamental band and the ν3 + ν4 combination bands.47 The presence of additional
νCN absorption bands for 3Ni is presumably owing to the presence of a second Ni(II)
species due to the solvento loss of 3Ni (Figure 2.22).
Without exception, the energies of the two νCN absorptions for the coordinated
MeCN of complexes 1M-4M (M = Mn, Fe, Co, Ni) are higher than those of the free MeCN
(2253 cm-1 and 2293 cm-1). This is presumably because: the nitrogen atom long pair of
the nitrile has some C-N σ-antibonding character; the donation of this electronic density
to an empty orbital of a metal ion will strengthen the C-N σ-bond, thus increasing the
stretching frequency of C≡N.48 With complexes 1M-4M (M = Mn, Fe, Co, Ni), the
energies of both νCN absorption bands increase from Mn to Ni: the two νCN absorptions of
94
4M (M = Mn, Fe, Co, Ni) increase from 2280 cm-1 to 2290 cm-1, and from 2308 cm-1 to
2316 cm-1, respectively, as the metal center changes from Mn to Ni. This trend
qualitatively coordinates with the ligand field stabilization energy of Mn to Ni.45 This
observation further supports the discussion above that the increase of the stretching
frequency of CN is due to σ donation of electron density from the nitrogen atom long pair
of nitrile. On the other hand, the scorpionate ligands show much less of an effect on the
stretching frequency of CN than the metal ions, as indicated by the comparison of νCN
absorption bands of 2Ni and 4Ni (Figure 2.24).
95
Table 2.14. FT-IR νCN absorption bands of [(L)M(NCMe)3](BF4)2 (1M-2M; L = TpmMe,Me ,
TpmPh; M= Mn, Fe, Co, Ni) as KBr pellets.
Metal ion
TpmMe,Me (1M)
νCN, cm-1
TpmPh (2M)
νCN, cm-1
Mn
2313
2281
2308
2280
Fe
2313
2283
2308
2282
Co
2314
2287
2315
2290
Ni
2319
2291
2318
2290
Table 2.15. FT-IR νCN and νB-H absorption bands of [(L)M(NCMe)3]BF4 (3M-4M; L =
TpMe,Me , TpPh,Me; M= Mn, Fe, Co, Ni) as KBr pellets.
Metal ion
TpMe,Me (3M)
νB-H, cm-1
νCN, cm-1
νB-H, cm-1
TpPh,Me (4M)
νCN, cm-1
Mn
–
–
–
2550
2308
2280
Fe
2540
2311
2278
2548
2310
2281
Co
2526
2303
2287
2547
2314
2287
Ni
2523
2323
2298
2546
2316
2290
96
Figure 2.20. FT-IR spectra of [TpmMe,MeM(NCMe)3](BF4)2 (1M, M = Mn, Fe, Co, Ni)
showing the νCN absorption bands.
97
Figure 2.21. FT-IR spectra of [TpmPhM(NCMe)3](BF4)2 (2M, M = Mn, Fe, Co, Ni)
showing the νCN absorption bands.
98
Figure 2.22. FT-IR spectra of [TpMe,MeM(NCMe)3]BF4 (3M, M = Fe, Co, Ni) showing the
νCN and νB-H absorption bands.
99
Figure 2.23. FT-IR spectra of [TpPh,MeM(NCMe)3]BF4 (4M, M = Mn, Fe, Co, Ni) showing
the νCN and νB-H absorption bands.
100
Figure 2.24. FT-IR spectra of [TpmPhNi(NCMe)3](BF4)2 (2Ni, solid line) and
[TpPh,MeNi(NCMe)3]BF4 (4Ni, dashed line), emphasizing the effect of ligand on the νCN
absorption bands.
101
E. Magnetic Properties
The room temperature effective magnetic moments of complexes 1M-4M (M =
Mn, Fe, Co, Ni) were determined in CD3CN solution at room temperature by the Evans
NMR method.18 The results are summarized in Table 2.16. The observed µ eff values of
tris-acetonitrile Mn(II) complexes 1Mn, 2Mn and 4Mn are in a range of 5.90 - 5.94 µ B,
consistent with the expected spin only value (S = 5/2, 5.92 µ B).49 These values are also
comparable with 5.90 µ B, reported for [Mn(NCMe)4](BF4)2 (Table 2.17).17 The observed
µ eff values of neutral scorpionate ligand supported Fe(II) complexes 1Fe and 2Fe and
Co(II) complexes 1Co and 2Co are 5.87 µ B, 5.75 µ B, 4.99 µ B and 4.96 µ B, respectively,
while for anionic scorpionate ligand coordinated Fe(II) complexes 3Fe and 4Fe and Co(II)
complexes 3Co and 4Co, the observed moments are 5.62 µ B, 5.27 µ B, 4.80 µ B and 4.82 µ B,
respectively. These Fe(II) and Co(II) complexes all have µ eff values exceeding the spin
only values (FeII: S = 2, 4.90 µ B; CoII: S = 3/2, 3.87 µ B), but are within the range of what
is commonly observed for octahedral Fe(II) and Co(II) complexes.49,50 They are also
comparable with 5.59 µ B and 5.18 µ B, reported for [Fe(NCMe)6](BF4)2 and
[Co(NCMe)6](BF4)2, respectively (Table 2.17).17 The neutral scorpionate ligand
supported Fe(II) and Co(II) complexes have higher observed µ eff values than the
corresponding anionic scorpionate ligand supported analogues. This trend is also true for
the Ni(II) complexes 1Ni-4Ni, wherein the observed moments are 3.14 µ B, 3.01 µ B, 2.81 µ B
and 2.94 µ B, respectively. These observed values are slightly less than the reported value
for [Ni(NCMe)6](BF4)2 (3.22 µ B), but are still in good agreement with the spin only
values for two unpaired electrons (S = 1, 2.83 µ B).17,49
102
Table 2.16. Effective magnetic moments (µ eff) of complexes 1M-4M (M = Mn, Fe, Co, Ni)
in CD3CN at 295 K by Evans NMR method.
Complexes
Spin
µ eff, µ B
Multiplicity (observed)
µ eff, µ B
(typical values)
µ eff, µ B
(spin only)
1Mn
5/2
5.90
5.6 – 6.1
5.92
1Fe
2
5.87
5.0 - 5.9
4.90
1Co
3/2
4.99
4.7 - 5.5
3.87
1Ni
1
3.14
2.8 – 3.5
2.83
2Mn
5/2
5.94
5.6 – 6.1
5.92
2Fe
2
5.75
5.0 - 5.9
4.90
2Co
3/2
4.96
4.7 - 5.5
3.87
2Ni
1
3.01
2.8 – 3.5
2.83
3Fe
2
5.62
5.0 - 5.9
4.90
3Co
3/2
4.80
4.7 - 5.5
3.87
3Ni
1
2.81
2.8 – 3.5
2.83
4Mn
5/2
5.90
5.6 – 6.1
5.92
4Fe
2
5.27
5.0 - 5.9
4.90
4Co
3/2
4.82
4.7 - 5.5
3.87
4Ni
1
2.94
2.8 – 3.5
2.83
103
Table 2.17. UV-Vis, Magnetic Susceptibility and FT-IR data for [MII(NCMe)n](BF4)2 (n
= 4, M = Mn; n = 6, M = Fe, Co, Ni) (literature values).17
MII
ν(CN), cm-1
µ eff, µ B.
Mn
2312(m), 2284(m)
5.90
Fe
2310(m), 2287(m)
5.59
Co
2316(m), 2292(m)
5.18
Ni
2316(m), 2292(m)
3.22
λ, nm
ε, M-1 cm-1
536
0.3
408
1.2
912
2.8
1017a
3.2
492
11.3
476
11.0
958
3.1
3
T2g(F) ← 3A2g
582
2.5
3
T1g(F) ← 3A2g
358
10.8
3
T1g(P) ← 3A2g
Assignment
4
T1g(G) ← 6A1g
4
Eg(G) ← 6A1g
5
4
Eg ← 5T2g
T2g(F) ← 4T1g(F)
Infrared: Samples were prepared as nujol mulls placed between KBr plates.
UV-Vis: MeCN was used as solvent. a Data was recorded by SL.
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108
CHAPTER 3: NITRENE TRANSFER CATALYSIS MEDIATED BY TRANSITION
METAL SCORPIONATE COMPLEXES
Transition metal catalyzed nitrene transfer reactions are among the most attractive
methodologies for the syntheses of valuable nitrogen-containing compounds such as
aziridines and amines.1-5 Various transition metals including manganese,6-8 cobalt,9
copper,4,10,11 silver,4,12,13 gold,14,15 ruthenium,16 and rhodium17 complexes have been
shown to induce these transformations. Among them, copper- or rhodium-mediated
aziridination and amination reactions are the well-established protocols for C-N bond
formation. However, precious or toxic metals are commonly involved in these reactions.
In contrast, earth-abundant 3d metals are inexpensive and may be more biocompatible,
yet have received sparse attention as potential practical catalysts for olefin aziridination
or C-H bond amination.
Mansuy and co-workers were the first to report an iron catalyzed intermolecular
alkene aziridination using [Fe(TTP)Cl] as catalyst and PhI=NTs as a nitrene precursor.6
A disparate range of iron complexes induce the conversion of alkenes to the
corresponding
aziridines:
Hossian’s
Lewis
acidic
iron(II)
complex,
[(η5-
C5H5)Fe(CO)2(THF)]BF4;18 Latour’s mixed-valent diiron complex bearing a hexadentate
phenol ligand;19 Zhou’s iron phthalocyanine complex;20 Halfen’s polyamine ligands
supported iron complexes;21 Che’s iron complex [Fe(Cl3terpy)2]22 and Bolm’s Fe(OTf)2
systems.23 More recently, Jenkins and co-workers also observed catalytic reactivity using
a macrocyclic tetracarbene iron complex, which catalyzed the aziridination of a wide
variety of aliphatic alkenes with aryl azides.24
109
On the other hand, iron-mediated C-H bond amination reactions are less well
developed than the analogous olefin aziridinations. Breslow and co-workers reported the
first example of an iron complex induced nitrene C-H bond insertion. [Fe(TTP)Cl]
catalyzed the conversion of cyclohexane to cyclohexane sulfonamide with only 3.1%
yield.25 Zhou and co-workers have shown that iron phthalocyanine is capable of
catalyzing intermolecular amination of organic substrates containing benzylic, tertiary or
allylic C-H bonds,20 while Che and co-workers evaluated the intramolecular C-H bond
nitrene insertion reactions of sulfamate esters and PhI(OAc)2 with the iron complex
[Fe(Cl3terpy)2].22 Recently, Betley and co-workers reported the first isolated iron(III)imido complex (ArL)Fe(N(p-tBuC6H4)Cl that is able to transfer the imido moiety to
benzylic C-H bond of toluene.26
In the pursuit of efficient and inexpensive transition metal catalysts for C-N bond
formation reactions, we employ the scorpionate ligand-supported tris-acetonitrile metal
complexes [(L)M(NCMe)3](BF4)n (1M, L = TpmMe,Me, M = Mn, Fe, Co, Ni, n = 2; 2M, L =
TpmPh, M = Mn, Fe, Co, Ni, n = 2; 3M, L = TpMe,Me, M = Fe, Co, Ni, n = 1; 4M, L =
TpPh,Me, M = Mn, Co, Fe, Ni, n = 1) as catalysts for the aziridination of alkenes and
amination of C-H bonds of hydrocarbons in the present work. The inspiration for our
investigation is the scorpionate-supported Cu(I) complexes recently employed by Pérez
and co-workers as a family of efficient metal catalysts for the aziridination of olefins and
C-H bond amination reactions of inert hydrocarbons.4,27,28 Our scorpionate-supported
metal complexes 1M-4M might exhibit similar reactivities toward olefin C=C bond
aziridination, as well as aromatic and benzylic C-H bond amination.
110
Aziridination Reactions of Olefins
We presented the synthesis and characterizations of 1M-4M (M = Mn, Fe, Co, Ni)
in the previous chapter. In our initial investigation of reactivity, scorpionate complexes
1M-4M as well as the Fe(II) salt [Fe(NCMe)6](BF4)2 were examined as potential catalysts
for the aziridination of styrene using PhI=NTs as nitrene precursor. In all cases, the
reactions were carried out at room temperature using 5 mol% metal catalyst and a styrene
to PhI=NTs (0.2 mmol) ratio of 5:1. The results are summarized in Table 3.1. It was
found that the Fe(II) complexes gave the desired aziridine 2 in good yield ranging from
51% to 94%, with complete consumption of PhI=NTs in less than 5 min (Table 3.1,
entries 2, 6, 9, 13). Interesting, when TpmPh or TpPh,Me (bearing phenyl substituents on 3position of pyrazole rings) coordinated Fe(II) complexes (2Fe, 4Fe) were used as catalyst,
the yield of the aziridine 2 was found to be much lower than those of the analogous Fe(II)
complexes 1Fe and 3Fe supported by TpmMe,Me and TpMe,Me ligands (bearing methyl
substituents on 3-position of pyrazole rings), respectively. This is presumably due to the
intramolecular aromatic C-H bond amination of the phenyl groups on the ligands,29-31
which in turn, lowers the catalytic activities of these metal catalysts. The desired aziridine
product 2 was also obtained when Mn(II), Co(II) or Ni(II) analogues were introduced as
nitrene transfer catalyst, although the yields were much lower than those of Fe(II)
analogues (Table 3.1). Therefore, among the various metal catalysts summarized in Table
3.1, [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) was found to be the most efficient catalyst for the
aziridination reaction of styrene with PhI=NTs.
111
Table 3.1. Complexes 1M-4M and [Fe(CH3CN)6](BF4)2 catalyzed aziridination of styrene
with PhI=NTs.
Entry
Catalyst
Reaction time
Yield (%)a
1
[TpmMe,MeMn(CH3CN)3](BF4)2
120 min
18
2
[TpmMe,MeFe(CH3CN)3](BF4)2
30 minb
94
3
[TpmMe,MeCo(CH3CN)3] (BF4)2
60 min
19
4
[TpmMe,MeNi(CH3CN)3](BF4)2
120 min
16
5
[TpmPhMn(CH3CN)3](BF4)2
100 min
17
6
[TpmPhFe(CH3CN)3](BF4)2
30 minb
63
7
[TpmPhCo(CH3CN)3](BF4)2
40 min
30
8
[TpmPhNi(CH3CN)3](BF4)2
100min
16
9
[TpMe,MeFe(CH3CN)3]BF4
30 minb
89
10
[TpMe,MeCo(CH3CN)3]BF4
60 min
42
11
[TpMe,MeNi(CH3CN)3]BF4
140 min
30
12
[TpPh,MeMn(CH3CN)3]BF4
120 min
18
13
[TpPh,MeFe(CH3CN)3]BF4
30 minb
51
14
[TpPh,MeCo(CH3CN)3]BF4
60 min
42
15
[TpPh,MeNi(CH3CN)3]BF4
120 min
15
16
[Fe(CH3CN)6](BF4)2
30min
--
17c
[Fe(CH3CN)6](BF4)2
30min
71
Ratio of substrate to PhINTs is 5:1. a Isolated yield. b Complete dissolution of PhINTs is less than
5 min. c CH3CN as solvent.
112
Encouraged by these results, we then further optimized the catalytic activity of the
iron(II) complex [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) toward the aziridination reaction of
styrene with PhI=NTs in CH2Cl2 at room temperature. Without catalyst, no aziridine
product was observed even after 24 h, as indicated in Figure 3.1 and Table 3.2 (entry 1).
When 0.5 mol% 1Fe was loaded with the same amount of styrene and PhI=NTs (5:1
ratio), the conversion of styrene to 2-phenyl-N-tosylaziridine 2 was achieved in 62%
yield (Table 3.2, entry 2). However, the yield of aziridine 2 dropped to only 33% with 1.0
equivalent of styrene relative to PhI=NTs (Table 3.2, entry 3). The best result (94% yield)
was obtained when 5 mol% of 1Fe was used with a styrene to PhI=NTs mole ratio of 5:1
(Table 3.2, entry 5). Such a degree of conversion achieved by 1Fe exceeds those previous
described for Fe(II) mediated aziridination of styrene with PhI=NTs,6,18,20,21 and it is also
better than the aziridination of styrene using the analogous Cu(I) catalyst
[TpmRCu(NCMe)]BF4 in ionic liquid reported by Pérez and co-workers.28 Notably, the
solid nitrene precursor PhI=NTs was consumed in less than 5 min, which is much faster
than reported metal mediated aziridinations, except for an analogous aziridination
reported by Halfen and co-workers,21 with the Fe(II) complexes [(Me5dien)Fe(OTf)2] and
[(iPr3TACN)Fe(OTf)2] as catalysts. With the same styrene to PhI=NTs mole ratio (5:1), a
reasonable yield of aziridine 2 was still obtained when only 1 mol% of 1Fe was used
(Table 3.2, entry 4).
113
A
*
B
*
C
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
δ (ppm)
4.5
4.0
3.5
3.0
2.5
2.0
Figure 3.1. 1H NMR spectra of aziridination of styrene with PhI=NTs (ratio of 5:1;
CDCl3, 295 K): (A), without catalyst 1Fe, no aziridine product was observed after 24 h;
(B), with 5 mol% of 1Fe, observation of aziridine product; (C), pure aziridine. Peaks due
to residual solvent are marked “*”.
114
Table 3.2. [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) catalyzed aziridinations of styrene with
PhI=NTs.
Entry
substratea
mol.% cat.b
Reaction time
Yield (%)d
1
5
0
24 h
0
2
5
0.5
60 minf
62
3
1
0.5
120 mine
33
4
5
1
30 minc
75
5
5
5
30 minc
94
6
5
10
30 minc
85
a
Number of equiv. of substrate to PhINTs. b vs. PhINTs. c Complete dissolution of PhINTs is less
than 5 min. d Isolated yield, 100% conversion of PhINTs. e PhINTs was completely dissolved in
about 2 hours. f PhINTs was completely dissolved in 50 min.
115
Other nitrene precursors, such as tosylazide, chloramines-T and PhI=NNs, were
also tested for the aziridination of styrene using 1Fe as catalyst. Among them, TsN3 did
not exhibit any significant nitrene transfer reactivity at room temperature, while NaClNTs
and PhI=NNs led to the formation of unidentified products. Aziridination of styrene using
a phenyliodinane generated in situ was also studied. Thus, the reaction using 5 mol% of
1Fe and a combination of TsNH2 5 and PhI(OAc)2 6 as a potential nitrene source
proceeded smoothly, affording 2-phenyl-N-tosylaziridine 2 in 42% yield (Scheme 3.1).
Ts
N
O
O
S
NH 2
1
[Tpm*Fe(CH 3CN) 3](BF4 )2 (5 mol%)
CH3 CN, rt, 18h, PhI(OAc) 2 (6)
42%
5
O
2
O
S
in situ formation of nitrene precursor
N I
Scheme 3.1. Azirdination of styrene using TsNH2 5 and PhI(OAc)2 6 as nitrene source
catalyzed by [TpmMe,MeFe(CH3CN)3](BF4)2 (1Fe).
116
Having optimized the reaction conditions, the scope of olefin substrates was
further extended. Various other olefins 7-11 were examined for catalytic aziridination
using the most active complex 1Fe as catalyst. As summarized in Table 3.3, moderate to
good isolated yields (46-94%) of aziridine products were typically obtained at room
temperature in CH2Cl2, using 5 mol% of 1Fe and an olefin to PhI=NTs ratio of 5:1, with
complete consumption of PhI=NTs observed within 5 min. The use of styrene 1 led to
excellent yield of the corresponding aziridine 2 (Table 3.3, entry 1; Appendix 1).
Cyclohexene 7 and norbornene 8, as well as electron deficient trans-methyl cinnamate 11
also afforded moderate yields of the corresponding aziridines (Table 3.3, entries 2, 3, 6;
Appendices 7, 9, 4). When cyclohexene 7 was used, both the olefin aziridination product
12 (Appendix 7) and allylic C-H bond amination product 13 (Appendix 8) were observed
in 49% and 34% isolated yields, respectively. Notably, the aziridination reaction of transstilbene 10 gave no observed aziridine product; instead, an olefinic C-H bond amination
product 16 was isolated in 51% yield (Table 3.3, entry 5; Appendix 6), which was
confirmed by 1H,
13
C and COSY NMR spectra (Appendix 6). Aziridination of cis-
stilbene 9 led to the formation of a mixture of the aziridination product 15 (Appendix 5)
and the olefinic C-H bond amination product 16 in 2.5:1 ratio with 79% total yield (Table
3.3, entry 5). To the best of our knowledge, this is the first example of nitrene insertion
into the olefinic C-H bond of cis- or trans- stilbene.32
117
Table 3.3. Olefin aziridinations mediated by [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) with
PhI=NTs.
Entry
1
substratea
Reaction timeb
aziridines
Yield (%)c
30 min
94
NHTs
2
30 min
NTs
,
49, 34
12
3
13
30 min
51
NTs
14
4
30 min
,
57, 22
NTs
15
5
30 min
H
51
NHTs
16
6
a
30 min
CO2Me
NTs
17
Substrate to PhINTs is 5:1 b Complete dissolution of PhINTs in 5 min. c Isolated yield.
46
118
Aziridination of para-Substituented Styrenes
The relative rates of aziridination of a series of para-substituted styrenes (p-XC6H4CH2=CH; X = Me, H, Cl, CF3, NO2) were examined through competition
experiments. The experiments were conducted under reaction conditions in which a
mixture of equal amounts of styrene (0.2 mmol) and a para-substituted analog (0.2
mmol) was treated with PhINTs (0.2 mmol) for a period of 30 min at room temperature
in CH3CN, using 1Fe (5 mol%) as catalyst (Scheme 3.2). A 1H NMR example is shown in
Figure 3.3. The results are summarized in Table 3.4. A logarithmic plot of the quotient of
yields vs the Hammett parameter σp+ yields a linear relationship, from which a value of ρ+
= -0.93 is derived from the slope as indicated in Figure 3.2. The results reveal that
styrenes with electron-donating substituents are more reactive than unsubstituted styrene
toward aziridination reaction, while electron-withdrawing substituents retard rates of
aziridination. The observed ρ+ value of -0.93 is comparable to that aziridination reactions
of [RuVI(TPP)(NTs)2] (ρ+ = -1.1) reported by Che and co-workers,16 and it is 3.3-fold
larger in magnitude than styrene aziridination catalyzed by [TpMe,MeCu(C2H4)] (ρ+ =
-0.28), reported by Pérez and co-workers.33 Overall, the large negative ρ+ value reveals
that the aziridination reaction catalyzed by 1Fe is highly sensitive to the electronic effect
of the para-substituent of styrene; thus, an electrophilic intermediate, plausibly high
valent iron(IV)-imido complex, is involved in the aziridination reactions catalyzed by
[TpmMe,MeFe(NCMe)3](BF4)2 (1Fe).22
119
Scheme 3.2. Competition reaction of styrene and para-substituted styrene mediated by
[TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) with PhI=NTs.
Table 3.4. Experimental kY/kH and log(kY/kH) values.
X
σp
kY/kH
log(kY/kH)
Me
H
Cl
CF3
NO2
-0.17
0
0.23
0.54
0.78
2.2951
1
1.3204
0.3544
0.2876
0.3608
0
0.1207
-0.4505
-0.5412
0.6
0.4
Me
y = -0.9(2)x + 0.15(9)
R² = 0.8809
0.2
logkY/kH
Cl
0
H
-0.2
-0.4
CF3
NO2
-0.6
-0.8
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
σp
Figure 3.2. Hammett plot of experimentally determined log(kY/kH) value vs. Hammett
para-substituent constant σp.
3.04
3.02
2.98
2.95
1.00
0.27
0.71
2.43
2.42
2.38
2.36
2.26
3.84
3.83
3.82
3.81
3.78
3.76
3.76
3.74
3.93
1.55
7.35
6.79
2.28
7.33
7.28
7.26
7.24
7.21
7.20
7.19
8.21
0.36
7.87
7.84
2.03
0.45
0.72
8.15
8.12
120
Figure 3.3. 1H NMR spectrum (CDCl3, 295 K): Competition reaction of styrene and pnitrostyrene mediated by [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) with PhI=NTs; mesitylene
(0.1 mmol) as internal standard.
121
C-H bond Amination of Tetrahydrofuran
Encouraged by the results found for aziridination reactions of cyclohexene 7 and
trans-stilbene 10 using [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) as catalyst, in which nitrene
insertion into a C-H bond was observed, we then decided to examine the reactivity of
complexes 1M-4M, as well as metal salts [M(NCMe)6](BF4)2 (M = Mn, Fe, Co, Ni) toward
the amination of tetrahydrofuran 18. In a typical reaction, PhI=NTs (0.2 mmol) was
reacted with THF 18 (1 mL) at room temperature in CH3CN, in the presence of metal
catalyst (5 mol%) and 4 Å molecular sieves. The conversion yield of THF 18 to N(tetrahydro-2-furanyl)-toluenesulfonamide 19 was examined by 1H NMR (Appendix 20),
with mesitylene (0.1 mmol) as internal standard. The results are summarized in Table 3.5.
In all cases, the conversion of THF was achieved in yields from 32% to 99%. 1Fe gave the
best result (99% yield), comparable to that of amination of THF in ionic liquid using the
analogous Cu(I) catalyst [Tpm*,BrCu(NCMe)](BF4) reported by Pérez and co-workers.28
As indicated in Table 3.5, the anionic scorpionate ligand coordinated Fe(II) complexes
3Fe and 4Fe (Table 5, entries 9, 13) were found to be less active toward amination of THF
than those of neutral scorpionate ligand coordinated Fe(II) analogues 1Fe and 2Fe (Table
3.5, entries 2, 6). This is presumably due to 3Fe and 4Fe featuring electron rich anionic
scorpionate ligands, which reduces reactivity.4 The electrophilic amination using
[Fe(NCMe)6](BF4)2 was found to be more efficient than 3Fe and 4Fe (Table 3.5, entry 17),
which also supports the hypothesis described above. Not surprisingly, the use of
scorpionate ligands bearing phenyl groups on 3-pyrazolyl positions gave the amination
product in lower yield than the use of scorpionate ligands bearing methyl groups (Table
122
3.5, entry 2 vs 6; entry 9 vs 13). This is presumably due to the same hypothesis depicted
for the analogous aziridination reaction in which intramolecular amination of the phenyl
group on the scorpionate ligand reduces the catalytic activity of the catalyst. The
analogous Mn(II) catalysts were found to be the least reactive catalysts which gave yields
of amination product 19 lower than 40% (Table 3.5, entries 1, 5, 12, 16). As summarized
in Table 3.5, the Mn(II), Co(II) and Ni(II) salts all show comparable or better reactivity
than the analogous scorpionate ligand complexes. The catalytic ability of these metal
catalysts for C-H amination reactions is also clearly reflected by the necessary reaction
times. Reasonable conversion of THF 18 to 19 (71% yield) was still achieved when only
5 equivalents of THF relative to PhI=NTs was applied, with 1Fe as catalyst (Table 3.5,
entry 20).
In order to probe the rate-determining step of the C-H bond amination reaction of
THF catalyzed by 1Fe, a competition experiment employing a 1:1 ratio of THF to THF-d8
provided a kinetic isotope effect, kH/kD, of 1.4 for 1Fe (Figure 3.4). The KIE value is much
smaller than the classical KIE value for hydrogen atom transfer (6.5)26 and is thus
indicates that C-H bond cleavage step is not the rate-determining step in the amination
reaction of THF.
123
Table 3.5. Complexes 1M-4M catalyzed amination of THF with PhI=NTs.
Entry
Catalyst
Reaction timea
Yield (%)b
1
[TpmMe,MeMn(CH3CN)3](BF4)2
60 min
32
2
[TpmMe,MeFe(CH3CN)3] (BF4)2
30 min
99
3
[TpmMe,MeCo(CH3CN)3] (BF4)2
30 min
69
4
[TpmMe,MeNi(CH3CN)3] (BF4)2
30 min
74
5
[TpmPhMn(CH3CN)3] (BF4)2
60 min
33
6
[TpmPhFe(CH3CN)3] (BF4)2
30 min
68
7
[TpmPhCo(CH3CN)3] (BF4)2
30 min
60
8
[TpmPhNi(CH3CN)3] (BF4)2
30min
65
9
[TpMe,MeFe(CH3CN)3] BF4
30 min
67
10
[TpMe,MeCo(CH3CN)3] BF4
30 min
64
11
[TpMe,MeNi(CH3CN)3] BF4
50 min
66
12
[TpPh,MeMn(CH3CN)3] BF4
60 min
38
124
13
[TpPh,MeFe(CH3CN)3] BF4
30 min
36
14
[TpPh,MeCo(CH3CN)3] BF4
30 min
29
15
[TpPh,MeNi(CH3CN)3] BF4
40 min
60
16
[Mn(CH3CN)6] (BF4)2
30 min
34
17
[Fe(CH3CN)6] (BF4)2
30 min
82
18
[Co(CH3CN)6] (BF4)2
30 min
63
19
[Ni(CH3CN)6] (BF4)2
30 min
79
20c
[TpmMe,MeFe(CH3CN)3] (BF4)2
30 min
71
With 2 mL THF and 0.2 mmol PhINTs. a Complete dissolution of PhINTs varies. b 1H NMR yield
(with mesitylene as internal standard) based on the amount of PhINTs. C with THF to PhINTs in
5:1 ratio.
8.5
8.0
7.5
7.0
6.5
5.0
4.5
4.0
δ (ppm)
3.5
3.0
1.92
1.89
1.87
1.84
1.83
1.81
1.80
1.79
1.77
2.13
1.13
2.5
3.21
2.44
5.93
5.12
0.55
5.5
3.72
3.70
3.68
5.33
1.01
6.0
2.00
5.66
5.64
5.63
1.45
7.32
7.29
4.06
3.77
7.83
7.81
125
2.0
1.5
1.0
0.5
Figure 3.4. 1H NMR spectrum (CDCl3, 295 K): C-H bond amination prodcuts of
competition reaction of THF and THF-d8 catalyzed by 1Fe with PhI=NTs.
0.0
126
Having successfully achieved the C-H bond amination of THF which contains
weak C-H bond, we then decided to use 1Fe as catalyst to examine the C-H bond
amination of less reactive hydrocarbon substrates containing strong C-H bonds. Cyclic
alkane substrates cyclohexane 20 and cyclopentane 21 were first introduced in such
amination reactions. As depicted in Table 3.6, the C-H bond amination of cyclohexane 20
and cyclopentane 21 mediated by 5 mol% 1Fe in CH2Cl2 were found to give the
corresponding products (22, 23; Appendix 18, 19) in low isolated yields (40% and 30%,
respectively) after 5 hours. The conversion yields are much lower than the analogous
amination of tetrahydrofuran with 1Fe (Table 3.5, entry 2). And the amination yield of
cyclohexane 20 is also lower than that achieved by using of [TpBr3Cu(NCMe)] as catalyst
reported by Pérez and co-workers.27 The differences in activity shown between
cyclohexane or cylcopentane and tetrahydrofuran might be due to their C-H bond
dissociation energies, since cyclohexane and cyclopentane have higher bond dissociation
energies than that of tetrahydrofuran.4
Table 3.6. [TpmMe,MeFe(CH3CN)3] (BF4)2 (1Fe) catalyzed amination of cyclic alkane
substrates with PhI=NTs.
Reaction time
amines
Yield (%)b
Entry
substratea
a
1
30 min
45
2
30 min
60
2 mL Substrate and 0.2 mmol PhINTs, and 4 mL CH2Cl2 as solvent, at R.T. b Isolated yield.
127
C-H bond Amination of Aromatic Substrates
Following the preliminary investigation of inert cyclic alkane substrates, we then
expanded the substrate scope to aromatic hydrocarbons. In our initial investigation of CH amination of aromatic hydrocarbons, we employed PhI=NTs (0.2 mmol) as the nitrene
source and benzene 24 (2 mL) as substrate. After the reaction was run in CH2Cl2 at room
temperature with 5 mol% of 1Fe and 4 Å molecular sieves for 30 min (with complete
dissolution of PhI=NTs observed within 5 min), benzene 24 was converted into Ntosylaminobenzene 32 in 45% isolated yield (Table 3.7, entry 1; Appendix 10).
Introducing a nitrogen functional group into benzene is currently achieved by indirect
methods which require the pre-installation of functional groups such as nitro, chloro or
hydroxyl substituents, while examples of the direct amination of benzene are sparse.27
This is presumably due to the relatively high bond dissociation energy of the benzene CH bonds.4 With regard to the use of nitrene insertion methodologies, Ayyangar and coworkers reported a noncatalytic method which the reaction of tosylazide with benzene at
160 oC gave a very low yield of nitrene insertion product,34 while Pérez and co-workers
reported the conversion of benzene into N-tosylaminobenzene 32 using catalytic amount
of Cu(I) catalyst [TpBr3Cu(NCMe)] in 40% yield at room temperature.27,35
Encouraged by the exceptional catalytic reactivity of 1Fe towards the amination of
aromatic C-H bonds in benzene, we then examined the catalytic reactivity and
chemoselectivity with substrates containing both aromatic and benzylic C-H bonds. Thus,
aromatic substrates 25-31 bearing one, two or three alkyl substituents were examined
using reaction conditions similar to those used for benzene. To our surprise, the reaction
128
of PhI=NTs with mesitylene 31 in CH2Cl2 gave the aromatic C-H bond insertion product
45 in 81% yield at room temperature, with only a trace amount of the benzylic amination
product (Table 3.7, entry 8; Appendix 11). This behavior was not limited to mesitylene
31, since other mono- or di- methyl substituted benzene substrates were also found to
show excellent chemoselectivities toward aromatic C-H bonds in moderate to good
reaction yields (Table 3.7, entry 2, 5, 6, 7). The use of toluene 25 as substrate led to the
formation of a mixture of two products, the para and ortho derivatives (33, 34; 1.4:1
ratio, 60% overall yield; Appendix 17), as the result of the nitrene insertion into the para
and ortho C-H bonds of the benzene ring (Table 3.7, entry 2). Again, only a trace amount
of the benzylic C-H bond amination product was observed. Not surprisingly, the reactions
of PhI=NTs with o-xylene 29 or m-xylene 30 also gave the expected mixture of products
derived from the activation of aromatic C-H bonds (Table 3.7, entry 6, 7; Appendix 13,
14). The use of p-xylene 28 led to the formation of both aromatic and benzylic C-N bond
formation products 39 and 40 in 6.2:1 ratio (Table 3.7, entry 5; Appendix 12), which is
presumably due to the fact that the benzylic C-H bonds of p-xylene 28 are activated by
para methyl substituents, thus a considerable amount of product 40 was obtained.
However, when ethylbenzene 26 or isopropyl-benzene 27 containing secondary or
tertiary C-H bonds were used as the substrate, high percentages of benzylic C-H bond
nitrene insertion products 36 and 38 were observed (Table 3.7, entry 3, 4 Appendix 16,
17). As indicated in entry 3 and 4 in Table 3.7, nearly equal amounts of benzylic and
aromatic C-H insertion products were obtained.
129
He and co-worker reported a similar transformation of mesitylene using AuCl3 as
catalyst in which the nitrene fragment was exclusively inserted into aromatic C-H
bonds.15 However, when tertiary benzylic C-H sites are available, both aromatic and
benzylic tertiary C-H bond were functionalized. When less substituted benzenes or
benzene itself were studied as substrates, less than 5% yield of products derived from the
insertion of the nitrene fragment into the aromatic C-H bonds was obtained.15 As
mentioned above, the direct amination of benzene has been achieved by nitrene insertion
with [TpBr3Cu(NCMe)], as reported by Pérez and co-workers.27,35 However, they found
that when benzylic C-H bonds were available, such as in toluene and mesitylene, the C-H
bond amination ractions exclusive took place at the alkyl substitutents sites, with no
functionalization of aromatic C-H bonds.
Therefore, [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) shows unique reactivity and
chemoselectivity toward aromatic C-H bonds over primary benzylic C-H bonds, and it
also induces the functionalization of weak benzylic C-H sites as for p-xylene,
ethylbenzene or isopropylbenzene, along with the functionalization of aromatic C-H sites.
130
Table 3.7. Intermolecular C-H bond amination reaction of aromatic substrates mediated
by [TpmMe,MeFe(NCMe)3](BF4)2 (1Fe) with PhI=NTs.
Entry
substratea
Reaction timec
amines
Yield (%)b
1
30 min
45
CH3
2
Ts
N
H
30 min
,
60
33
1:1.4
3
30 min
,
62
1.1 : 1
4
H
H
27
CH3
H
CH3
30 min
,
57
1.1 : 1
CH3
5
30 min
Ts
N
H
,
39
66
CH3
6.1: 1
6
30 min
,
63
4: 1
7
30 min
,
H
Ts
N
CH3
74
H3C
44
4.9: 1
H
H
8
H3C
a
H
CH2
31
CH3
CH2
30 min
H3C
Ts
N
H
81
CH3
45
1 mL substrate or 2 mL substrate (for benzene and toluene substrates) and 0.2 mmol PhINTs, 4
mL CH2Cl2 as solvent, at R.T.. b Isolated yield. c Complete dissolution of PhINTs in 5 min.
131
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134
CHAPTER 4: MASKED LEWIS ACID [Fe(NCMe)6](BF4)2 CATALYZED
CYCLOADDITION REACTIONS
Nitrogen-containing heterocycles are commonly found in biologically active
compounds, natural products and pharmaceuticals,1-3 which play important roles in
modern medicinal and synthetic chemistry due to their specific biological behaviors and
remarkable structural diversities. Therefore, the search for innovative approaches toward
the synthesis of heterocyclic compounds is of great importance, as strained threemembered rings aziridines are versatile building blocks due to their facial ring opening
reactions with nuclophiles.4-6 These reactions have led to the formation of various
nitrogen-containing compounds. Among these, Lewis acid promoted formal [3+2]
cycloaddition reactions of aziridines to dipolarophiles have shown increasing promise
toward the formation of five-membered nitrogen-containing heterocycles, since such
heterocycles can be created in one step with high efficiency, chemoselectivity and atom
economy.7 Intense efforts have been contributed to the advancement of [3+2]
cycloaddition reactions involving azomethine ylides generated from the C-C bond
cleavage of aziridines.8,9 In contrast, the analogous transformations of aziridines to fivemembered nitrogen-containing heterocycles through C-N bond cleavage of aziridines are
less well explored. Mann and co-workers recently reported a uncommon zwitterionic 1,3dipole generated from 2-phenyl-N-tosylaziridine via C-N bond cleavage induced by the
addition of a stoichiometric amount of the Lewis acid BF3·Et2O.10 Since then, Lewis acid
promoted formal [3+2] cycloaddition reactions of aziridines via C-N bond cleavage with
alkenes,11 alkynes,12,13 aldehydes/ketones or organic nitriles,14-17 leading to the formation
135
of five-membered nitrogen-containing heterocycles, have been explored. Although this
reaction pattern frequently emerges in current reports, catalytic examples for the
synthesis of five-membered nitrogen-containing heterocycles are rare. Mann and coworkers reported the formation of pyrrolidine derivatives achieved by the cycloaddition
of 2-phenyl-N-tosylaziridine to alkenes using a stoichiometic amount of the Lewis acid
BF3·Et2O.10 The analogous transformation of aziridines to substituted pyrrolidines was
also induced by addition of catalytic amount of Sc(OTf)3 as reported by Yadav and coworkers.11 Formation of oxazoline derivatives through cycloadditions of aziridines to
carbonyl compounds using a stiochiometric amount of Cu(OTf)2 or catalytic quantity of
Sc(OTf)3 was reported by the Ghorai16 and Nguyen groups,14 respectively. More recently,
FeCl3 and AgSbF6 have been shown to act as efficient catalysts in the cycloaddition
reactions of aziridines with alkynes.12,13 However, many transformations of aziridines
require the presence of a stoichiometric amount of the Lewis acid (BF3·Et2O, Cu{OTf}2)
or heavy and rare metal catalysts (Sc{OTf}3, AgSbF6) to achieve the cycloaddition
products in good yields. On the other hand, iron is one of the most abundant metals on
earth and consequently is one of the most economical and environmentally friendly
metals.
Despite
its
advantages,
iron
catalysts
remain
surprisingly relatively
underdeveloped compared to other transition metals.18 As just mentioned, Wang and coworkers reported the formation of 2-pyrrolines via [3+2] cycloaddition of azridines with
arylalkynes catalyzed by FeCl3. However, no reactions were reported for aziridines and
other substrates such as alkenes.12
136
In the present chapter, we describe the in situ formation of a pyrrolidine derivative
generated from the reaction of styrene and PhI=NTs in CH2Cl2, a [2+1+2] cycloaddition
process induced by the presence of a catalytic amount of masked Lewis acid
[Fe(NCMe)6](BF4)2. We propose that a zwitterionic 1,3-dipole intermediate is produced
in this process via the C-N bond cleavage of 2-phenyl-N-tosylaziridine as reported by
Mann and co-workers.10 Inspired by the in situ formation of pyrrolidine derivatives with
styrene, we extend our reaction substrates to a variety of alkenes, aldehydes, ketones and
alkynes. We present various transformations of 2-phenyl-N-tosylaziridine to fivemembered nitrogen-containing heterocycles such as pyrrolidines, oxazolidines and 2pyrrolines in the presence of a catalytic amount of [Fe(NCMe)6](BF4)2.
The aziridination of styrene with PhI=NTs catalyzed by [Fe(NCMe)6](BF4)2 gave
71% isolated yield of aziridine product 2 in CH3CN as solvent (Table 3.1, entry 17),
while under the same reaction conditions, no aziridine was obtained in CH2Cl2 (Table 3.1,
entry 16). In fact, when a mixture of styrene (1.0 mmol), PhI=NTs (0.2 mmol) and
[Fe(NCMe)6](BF4)2 (5 mol%) in CH2Cl2 was stirred for 30 min at room temperature, we
noticed the formation of two diastereomeric products. After purification by column
chromatography on silica gel, the
1
H and
13
C NMR spectra of the inseparable
diastereomers were consistent with 2,4-diphenyl-1-tosyl-pyrrolidine 3 as cis and trans
isomers in a ratio of nearly 1:1 (Appendix 21).19 Based on the literature precedent, we
conclude that [Fe(NCMe)6](BF4)2 initially catalyzes the aziridination reaction of styrene
with PhI=NTs to form 2-phenyl-N-tosylaziridine 2, and then 2 further reacts in situ with
styrene to give rise to a pyrrolidine derivative 3 through a formal [3+2] cycloaddition
137
reaction induced by [Fe(NCMe)6](BF4)2 in CH2Cl2 (Scheme 4.1).10,11,20 We propose that
formation of a zwitterionic 1,3-dipole intermediate 2a is induced by [Fe(NCMe)6](BF4)2
in CH2Cl2, then the olefinic π system of styrene attacks at the benzylic position of the 1,3dipole intermediate 2a, giving rise to a stable benzylic carbocation 3a, which is then
attacked by the adjacent amide nucleophilie to form the pyrrolidine derivative 3 (Scheme
4.1). Significantly, this reaction provided pyrrolidine 3 as the only detectable
regioisomer, with no observation of pyrrolidine 4, presumably owing to the poor stability
and sterics of intermediate 4a. The use of different solvents was shown to lead to the
formation of different products; therefore, the formation of substituted pyrrolidine 3
suggested that [Fe(NCMe)6](BF4)2 may behave as an unmasked Lewis acid in CH2Cl2.
When CH3CN is used as the reaction medium, the Fe(II) center is protected by the
coordinated CH3CN molecules and loses its Lewis acidity. Therefore, the aziridine
product 2 is obtained, with no observation of [3+2] cycloaddition product 3. The
conversion of olefins into aziridines in CH3CN at 85 ºC using Fe(OTf)2 as catalyst and
PhI=NTs as nitrene source was reported by Bolm and co-workers. Without adding ligand,
only 23% yield of 2-phenyl-N-tosylaziridine 2 was obtained with styrene as substrate;
however, the formation of pyrrolidine derivatives was not observed.21 Therefore,
[Fe(NCMe)6](BF4)2 is unmasked as a Lewis acid, and to the best of our knowledge, our
reaction system is the first example of catalysis inducing the formation of pyrrolidine
derivatives arising from the reaction of simple alkenes with PhI=NTs as nitrene source.
138
Scheme 4.1. [2+1+2] cycloaddition reaction of styrene with PhI=NTs in CH2Cl2
catalyzed by [Fe(NCMe)6](BF4)2
139
[2+1+2] Cycloaddition of Alkenes with PhI=NTs
We initially investigated the scope and the generality of the in situ formation of
substituted pyrrolidines. The reactions were conducted in CH2Cl2 at room temperature in
the presence of 5 mol% of [Fe(NCMe)6](BF4)2 (Scheme 4.2). A variety of parasubstituted styrenes (0.5 mmol) bearing electron-donating and electron-withdrawing
groups were employed as the reaction substrates and PhI=NTs (0.2 mmol) was
introduced as the nitrene source. As indicated in Table 4.1, when the para substituent is
H-, methyl- or chloro-, a cis and trans mixture of substituted pyrrolidine isomers was
obtained in a ratio of nearly 1:1, which were inseparable on TLC (Table 4.1, entries 1-3).
The presence of an electron-donating methyl substituent on the para position of styrene
46 was shown to favor the cycloaddition reaction, with the reaction finished in 30 min,
and the corresponding pyrrolidine product 50 obtained in 70% yield (Appendix 22). In
contrast, the chloro substituent on the para position of styrene 47 appeared to retard the
reaction, with the product 51 obtained in 69% yield only after 2.5 hours (Appendix 23).
The para-substituted styrenes bearing strong electron-withdrawing groups such as NO249 and CF3- 48 gave the corresponding aziridination products 53 and 52 in moderate
yields, but no pyrrolidine derivatives were observed (Table 4.1, entries 4, 5; Appendices
2, 3). Therefore, the para substituents have significant effects on the formation of
pyrrolidine derivatives from styrenes. As indicated in Scheme 4.2, when para-substituted
styrene 1′ was used as substrate towards the [2+1+2] cycloaddition reaction with nitrene
precursor PhI=NTs, a [2+1] aziridination reaction occurred initially to generate a 2phenyl-N-tosylaziridine derivative 2′ in situ, in the presence of [Fe(NCMe)6](BF4)2 as
140
catalyst. Then 2′ was activated by [Fe(NCMe)6](BF4)2 in the non-coordinating solvent
CH2Cl2 to form a zwitterionic 1,3-dipole intermediate 2a′ via C-N bond cleavage, which
was then attacked by the olefinic π system of para-substituted styrene at the benzylic
position of 2a′, giving rise to benzylic cation 3a′. At last, intramolecular ring closure of
3a′ with the adjacent amide gives the substituted pyrrolidine product 3′. Overall, this
reaction process constitutes a [2+1+2] cycloaddition reaction to generate pyrrolidine
derivatives. As indicated in Scheme 4.2, the two charges of the zwitterionic 1,3-dipole
intermediate 2a′ are stabilized in an exo by both the tosyl and phenyl groups. Thus, an
electron-donating substituent on the para position of the phenyl ring stabilizes the
zwitterionic intermediate, while this intermediate is destabilized by an electronwithdrawing substituent on the para position of the phenyl ring. Therefore, parasubstituted styrene substrates with electron-donating groups lead to the formation of the
desired pyrrolidine products, while the analogous para-substituted styrene substrates
bearing electron-withdrawing groups disfavored the desired [2+1+2] cycloaddition
reactions, and only the [2+1] aziridination reactions were achieved (Table 4.1, entries 45).
Under similar reaction conditions, other alkenes were also introduced as
substrates to examine the formation of pyrrolidine derivatives (Table 4.1, entries 6-7).
Unfortunately, both trans-stilbene 10 and cyclohexene 7 showed no reactivity towards
formation of pyrrolidine derivatives. The reactions of trans-stilbene 10 and cyclohexene
7 with PhI=NTs catalyzed by [Fe(NCMe)6](BF4)2 in CH2Cl2 showed similar results as
those described in the previous chapter using [TpmMe,Me(NCMe)3](BF4)2 (1Fe) as catalyst.
141
The reaction of trans-stilbene 10 with PhI=NTs gave the olefinic C-H bond amination
product 16 in 40% yield (Appendix 6). The formation of 2,3,4,5-tetraphenyl-pyrrolidine
from trans-stilbene is presumably disfavored by the steric hindrance. Both aziridination
product 12 and C-H bond amination product 13 were obtained in 17% overall yield with
cyclohexene 7 as substrate (Appendices 7, 8). This result shows that the formation of a
zwitterionic 1,3-dipole intermediate from a nonactivated alkene (as for cyclohexene) is
not favorable.
The results described above demonstrate that the formation of pyrrolidine
derivatives via [2+1+2] cycloaddition reactions of alkenes and PhI=NTs catalyzed by
unmasked Lewis acid [Fe(NCMe)6](BF4)2 in CH2Cl2, is controlled by the electronic
nature and steric effect of the alkene substrates.
142
Table 4.1. [2+1+2] cycloaddition of olefins with PhI=NTs in the presence of unmasked
Lewis acid [Fe(NCMe)6](BF4)2 in CH2Cl2.
Entry
substratea
1
2
H3C
Reaction time c
Yield (%)b
product
30 min
55 (d.r. 1:1.1)
30 min
70 (d.r. 1:1.2)
2.5 h
69 (d.r. 1:1)
46
3
4
5h
65
5
5h
64
6
3h
40
F3C
48
10
NHTs
7
80 min
NTs ,
12
a
17
13
1.0 mmol substrate and 0.2 mmol PhINTs, with 3 mL CH2Cl2 as solvent, at R.T. b Isolated yield.
c
Complete dissolution of PhINTs in 5 min.
143
R
Ts
N
PhI=NTs
1'
R
R Fe(CH3CN)6(BF4)2
CH2Cl2
R = Me, H, Cl, CF3, NO2
1'
2'
Fe(CH3CN)6(BF4)2
R
CH2Cl2
N
Ts
R
3'
C-N breaking
R
R
N
Ts
1'
R
N
Ts
2a'
R
3a'
Scheme 4.2. [2+1+2] cycloaddition reaction of para-substituted styrene with PhI=NTs in
CH2Cl2 mediated by unmasked Lewis acid [Fe(NCMe)6](BF4)2.
144
[3+2] Cycloadditon of Aziridine with Alkenes, Aldehydes, Ketones and Alkynes
The cycloaddition reaction of aziridines with dipolarophiles represents an
innovative approach to the formation of heterocycles such as pyrrolidine,10,11
pyrroline,12,13 oxazolidine15 and imidaolines.15-17 Encouraged by the catalytic reactivity of
the unmasked Lewis acid [Fe(NCMe)6](BF4)2 in [2+1+2] cycloaddition of alkenes with
PhI=NTs, we examined its catalytic reactivity in the formal [3+2] cycloaddition reaction
of pre-formed 2-phenyl-N-tosylaziridine with various dipolarophiles, including
arylalkenes, aldehydes, ketones, alkynes and nitriles (Scheme 4.3). Table 4.2 outlines the
scope of [Fe(NCMe)6](BF4)2 catalyzed condensation reactions of 2-phenyl-Ntosylaziridine 2 to various dipolarophile substrates in CH2Cl2 at room temperature. Under
optimized reaction conditions, a wide variety of nitrogen-containing heterocycles was
obtained with high regioselectivity and moderate to good isolated yields.
Cycloadditions of 2-phenyl-N-tosylaziridine 2 with p-methylstyrene 46 and pchlorostyrene 47 in CH2Cl2 at room temperature were shown to produce substituted
pyrrolidines 60 (Appendix 24) and 61 in a cis/trans ratio of approximately 1:1, in 80%
and 67% yields, respectively (Table 4.2, entries 1-2). Unlike the in situ formation of
pyrrolidine derivatives via cycloaddition of para-substituted styrenes and PhI=NTs,
which were carried out with low catalyst loading (5 mol%, Table 4.1, entries 1-3), the
reactions of 2-phenyl-N-tosylaziridine 2 with p-methylstyrene 46 and p-chlorostyrene 47
require higher catalyst loading (10 mol%) in order to obtain high conversions and yields.
145
Scheme 4.3. Formal [3+2] cycloaddition of aziridine 2 with various dipolarophiles
mediated by [Fe(NCMe)6](BF4)2.
Scheme 4.4. Hydrolysis of 1,3-oxazolidine derivative 64 to 1,2-amino alcohol 69.
146
The complete conversion of 2-phenyl-N-tosylaziridine into 1,3-oxazolidines was
achieved with aldehyde or ketone substrates using 20 mol% of [Fe(NCMe)6](BF4)2.
Interestingly, the diastereoselectivity of the 1,3-oxazolidine products largely depends on
the reaction time and the amount of catalyst. When reaction of 2-phenyl-N-tosylaziridine
2 (0.2 mmol) with benzaldehyde 54 (0.5 mmol) was conducted in CH2Cl2 at room
temperature using 10 mol% [Fe(NCMe)6](BF4)2 as catalyst, the diastereomeric ratio of 62
was 5.7:1 (cis:trans) with 90% conversion of 2-phenyl-N-tosylaziridine 2 after 60 min.
However, when the reaction was carried out with 20 mol% [Fe(NCMe)6](BF4)2, the 2phenyl-N-tosylaziridine 2 was all consumed after 2 hours and a cis and trans mixture of
1,3-oxazolidine 62 in a 1:1.2 ratio were obtained (Table 4.2, entry 3; Appendix 25). This
observation is presumably due to isomerization of the kinetically formed cis isomer to the
trans isomer via C-O bond cleavage of 1,3-oxazolidine induced by [Fe(NCMe)6](BF4)2.
This cis to trans isomerization process of 1,3-oxazolidines has also been observed by the
Nguyen14 and Ghorai groups16, respectively. Meanwhile, reactions of 2-phenyl-Ntosylaziridine 2 with 4-methylbenzaldehyde 55 and acetophenone 56 also gave the
desired 1,3-oxazolidine derivatives 63 and 64, respectively, in the presence of 20 mol%
of [Fe(NCMe)6](BF4)2 (Table 4.2, entries 4-5; Appendices 26-27). Interestingly, when the
isolated 1,3-oxazolidine derivative 64 was kept in an NMR tube in CDCl3 for about 30
days, hydrolysis of 64 to the corresponding 1,2-amino alcohol 69 (Appendix 28) was
observed (Scheme 4.4).16
The formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine was also examined
with alkynes as dipolarophiles using 20 mol% of [Fe(NCMe)6](BF4)2 (Table 4.2, entries
147
6-7). Reactions were conducted in CH2Cl2 at room temperature with an alkyne to 2phenyl-N-tosylaziridine mole ratio of 3:1. In order to achieve high conversion of 2phenyl-N-tosylaziridine, longer reaction times were required for the reactions with
alkynes, compared with the reactions with alkenes, aldehydes and ketones as
dipolarophiles. The reaction of 2-phenyl-N-tosylaziridine 2 with 1-phenyl-1-propyne 58
afforded substituted 2-pyrroline 67 as the only regioisomer in 68% isolated yield after 4
hours (Table 4.2, entry 7; Appendix 30). A 1.4:1 mixture of two regioisomeric 2pyrroline derivatives 65 and 66 was obtained from the reaction of 2-phenyl-Ntosylaziridine 2 with phenylacetylene 57 after 4 hours (Table 4.2, entry 6; Appendix 29).
Analysis of the NMR spectrum of the major product 65 was consistent with 2,4-diphenyl2-pyrroline reported by Wender and co-workers.13 The structure of the minor product was
assigned to 2,5-diphenyl-2-pyrroline 66 based on a COSY experiment; the J-coupling
excludes the formation of 70 and 71 (Scheme 4.5). Our proposed mechanism for the
observation of two regioisomeric products of the reaction of 2 and 58 is shown in Scheme
4.5. As indicated in Scheme 4.5, two C-N bonds of 2-phenyl-N-tosylaziridine 2 are
theoretically in competition. Thus, it is proposed that the reaction involves two possible
zwitterionic 1,3-dipole intermediates 2a and 2b. 2a and 2b are attacked by
phenylacetylene 58, generating two stable benzylic like carbocations 65a and 66a,
respectively, which then undergo intramolecular cyclizations, giving rise to the desired 2pyrroline derivatives 65 and 66. As expected, the more stable zwitterionic 1,3-dipole
intermediate led to the formation of 65 as the major product.
148
As expected, the formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine 2 with
acetonitrile 59 using masked Lewis acid [Fe(NCMe)6](BF4)2 as catalyst did not form the
desired substituted imidazoline product 68 (Table 4.2, entry 8). This is presumably due to
the coordination of nitrile to the iron(II) center, thus disabling its catalytic reactivity.
In conclusion, we have discovered that unmasking of the Lewis acid
[Fe(NCMe)6](BF4)2 effects the construction of substituted pyrrolidines from the reaction
of arylalkenes with nitrene precursor PhI=NTs. This iron(II) catalyst has also been
employed to induce the formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with
various dipolarophiles such as alkenes, carbonyls and alkynes, for the synthesis of fivemembered nitrogen-containing heterocycles; excellent yields and regioselectivity has
been achieved in these cycloaddition reactions.
149
Table 4.2. [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with various dipolarophiles
in the presence of unmasked Lewis acid [Fe(NCMe)6](BF4)2 in CH2Cl2.
Entry
substratea
mol.% cat.
Reaction time
product
Yield (%)b
1
10
40 min
80
2
10
2h
67c
3
20
2h
87
4
20
2h
90
5
20
2h
79
6
20
4h
64
NTs
65
1.4:1
N
Ts
66
CH3
7
20
4h
68
20
4h
~0
58
8
a
0.5 mmol substrate and 0.2 mmol aziridine, and 3 mL CH2Cl2 as solvent, at R.T. b Isolated yield.
c
70% conversion of aziridine.
150
N
H
Ts
N
65
Ts
H
70
not observed
more stable
Ts
N
N
H
N
Fe(CH3CN)6(BF4)2
CH2Cl2
2
2a
58
Ts
Ts
N
Ts
H
H
H
65a
C-N breaking
stable cation
favorable
70a
unstable cation
unfavorable
less stable
Ts
N
2
58
2b
H
N
N
Fe(CH3CN)6(BF4)2
CH2Cl2
C-N breaking
Ts
Ts
71a
N
Ts
H
H
H
66a
stable cation
favorable
H
N
unstable cation
unfavorable
Ts
66
N
71
Ts
H
not observed
Scheme 4.5. Proposed mechanism showing the formation of 2-pyrroline derivatives from
the cycloaddition of aziridine 2 and phenylacetylene 57 with [Fe(NCMe)6](BF4)2.
151
Experimental Procedures for Chapter 3 and Chapter 4
General methods: All materials purchased from commercial suppliers were ACS
reagent-grade or better and used without further purification unless noted. Liquid organic
substrates were ACS reagent-grade or better and purified by either vacuum distillation
over calcium hydride or drying over 4 Å molecular sieves, and followed by the freezepump-thaw method prior to use. Dichloromethane and acetonitrile were degassed and
distilled over CaH2 before use. All reactions were performed in oven-dried glassware
under an Argon atmosphere. Organic solutions were concentrated under reduced pressure
by rotary evaporation. Thin layer chromatography plates were visualized by ultraviolet
light. Flash chromatography was carried out by using forced-flow method on 32–63D
60Å silica gel. 1H, 13C NMR and 2D NMR (COSY) spectra were recorded with a Bruker
Avance 300 MHz NMR spectrometer and were referenced internally according to the
TMS resonance.
Preparation of N-tosyliminophenyliodinane (PhI=NTs): PhI=NTs was prepared
based on a literature procedure.22 Iodosobenzene diacetate (9.60 g, 30 mmol) was
gradually added to a methanol solution (120 ml) of p-toluene-sulfonamide (5.12 g, 30
mmol), potassium hydroxide (KOH) (4.20 g, 75 mmol) below 10 ºC with stirring. The
resulting yellow homogeneous solution was stirred for three hours at room temperature.
After the reaction, the mixture was poured into distilled water to precipitate a yellow
colored solid on standing overnight, which was recrystallized from hot methanol to give
PhI=NTs in 5.6 g (yield: 50%).
152
Typical procedure for aziridination: To a stirred solution of alkene (1.0 mmol)
and metal catalyst in anhydrous CH2Cl2 (3 mL) was added solid PhI=NTs (0.2 mmol) in
one portion at room temperature under argon. The reaction mixture was then allowed to
stir for a certain time based on the dissolution of solid PhI=NTs. Upon completion the
reaction mixture was filtered through a plug of silica gel eluting with ethyl acetate and
the filtrate was concentrated under vacuum. Then the residue was applied to column
chromatography to afford the purified product.
Competition experiment for Hammett plot: To a stirred solution of styrene (0.2
mmol), para-substituted styrene (0.2 mmol) and [TpmMe,MeM(CH3CN)3](BF4)2 1Fe (5
mol%) in anhydrous CH3CN (3 mL) was added solid PhI=NTs (0.2 mmol) in one portion
at room temperature under argon. The reaction mixture was then stirred for 30 min at
room temperature. Upon completion the reaction mixture was filtered through a plug of
silica gel eluting with ethyl acetate and the filtrate was concentrated under vacuum. The
yields of aziridines were then analyzed by 1H NMR with mesitylene (0.1 mmol) as
internal standard to determine the amount of unreacted styrene and para-substituted
styrene.
Calculations:
kY/kH = log(Yf/Yi) / log(Hf/Hi)
Yf and Yi: the final and initial quantities of para-substituted styrene.
Hf and Hi: the final and initial quantities of styrene.
Typical procedure for C-H bond amination reactions: To a stirred solution of
organic substrate and [TpmMe,MeM(CH3CN)3](BF4)2 1Fe (5 mol%) in anhydrous CH2Cl2
153
(4 mL) with 4 Å molecular sieves was added solid PhI=NTs (0.2 mmol) in one portion at
room temperature under argon. The solid PhI=NTs was completely dissolved in less than
5 min. Then the reaction mixture was stirred for 30 min at room temperature. Upon
completion the reaction mixture was filtered through a plug of silica gel eluting with
ethyl acetate and the filtrate was concentrated under vacuum. Then the residue was
applied to column chromatography to afford the purified product. The THF C-H bond
amination product tosylamino tetrahydrofuran 19 was not further purified by column
chromatography, the crude product was analyzed by 1H NMR with mesitylene (0.1
mmol) as internal standard to determine the yield of 19.
General procedure of [Fe(CH3CN)6](BF4)2 mediated [2+1+2] cycloaddition of
nitrene to alkenes: To a stirred solution of alkene (1.0 mmol) and [Fe(CH3CN)6](BF4)2 (5
mol%) in anhydrous CH2Cl2 (3 mL) was added solid PhI=NTs (0.2 mmol) in one portion
at room temperature under argon. The reaction mixture was then allowed to stir for 30
min – 5h based on the alkene substrates used. Upon completion the reaction mixture was
the filtered through a plug of silica gel eluting with ethyl acetate and filtrate was
concentrated under vacuum. Then the residue was applied to column chromatography to
afford the purified product.
General procedure of [Fe(CH3CN)6](BF4)2 mediated [3+2] cycloaddition of 2phenyl-N-tosylaziridine to dipolarophiles: Iron(II) salt Fe[(CH3CN)6](BF4)2 (10-20
mol%) was added into CH2Cl2 solution (3 mL) with 2-phenyl-N-tosylaziridine 2 (54.7
mg, 0.2 mmol) and dipolarophile (0.5 mmol alkene, aldehyde, ketone, alkyne or
acetonitrile) under argon. The reaction mixture was then stirred at room temperature.
154
Upon complete formation of the aziridine 2 (determined by 1H NMR), the reaction
mixture was filtered through a plug of silica gel eluting with ethyl acetate and the filtrate
was concentrated under vacuum. Then the residue was applied to column
chromatography to afford the purified product.
References
(1) Butler, M. S. J. Nat. Prod. 2004, 67, 2141-2153.
(2) O'Hagan, D. Nat. Prod. Rep. 2000, 17, 435-446.
(3) Hili, R.; Yudin, A. K. Nat. Chem. Biol. 2006, 2, 284-287.
(4) Yudin, A. K. Aziridines and Epoxides in Organic Synthesis 2006.
(5) Hu, X. E. Tetrahedron 2004, 60, 2701-2743.
(6) Krake, S. H.; Bergmeier, S. C. Tetrahedron 2010, 66, 7337-7360.
(7) Dauban, P.; Malik, G. Angew. Chem., Int. Ed. 2009, 48, 9026-9029.
(8) Coldham, I.; Hufton, R. Chem. Rev. 2005, 105, 2765-2809.
(9) Pandey, G.; Banerjee, P.; Gadre, S. R. Chem. Rev. 2006, 106, 4484-4517.
(10) Ungureanu, I.; Klotz, P.; Mann, A. Angew. Chem., Int. Ed. 2000, 39, 4615-4617.
(11) Yadav, J. S.; Reddy, B. V. S.; Pandey, S. K.; Srihari, P.; Prathap, I. Tetrahedron
Lett. 2001, 42, 9089-9092.
(12) Fan, J. M.; Gao, L. F.; Wang, Z. Y. Chem. Commun. 2009, 5021-5023.
(13) Wender, P. A.; Strand, D. J. Am. Chem. Soc. 2009, 131, 7528-7529.
(14) Kang, B. M.; Miller, A. W.; Goyal, S.; Nguyen, S. T. Chem. Commun. 2009, 3928.
(15) Gandhi, S.; Bisai, A.; Prasad, B. A. B.; Singh, V. K. J. Org. Chem. 2007, 72, 21332142.
155
(16) Ghorai, M. K.; Ghosh, K. Tetrahedron Lett. 2007, 48, 3191-3195.
(17) Prasad, B. A. B.; Pandey, G.; Singh, V. K. Tetrahedron Lett. 2004, 45, 1137-1141.
(18) Beller, M.; Bolm, C., Transition Metals for Organic Synthesis. 2nd ed.; WileyVCH: Weinheim, 2004.
(19) Kelleher, S.; Quesne, P. Y.; Evans, P. Beilstein J. Org. Chem. 2009, 5.
(20) Ungureanu, I.; Bologa, C.; Chayer, S.; Mann, A. Tetrahedron Lett. 1999, 40, 53155318.
(21) Nakanishi, M.; Salit, A. F.; Bolm, C. Adv. Synth. Catal. 2008, 350, 1835-1840.
(22) Yamada, Y.; Yamamoto, T.; Okawara, M. Chem. Lett. 1975, 361-362.
156
CHAPTER 5: OXENE AND NITRENE CHEMISTRY OF Ni(0) MEDIATED BY
TRIS(3,5-DIMETHYLPYRAZOL-1-YL)METHANE
The oxo wall formalism rationalizes the scarcity of tetragonal oxo complexes for
transition metals to the right of the iron triad to occupancy of π* orbitals, which reduces
metal-oxo bond order.1 Nonetheless, a few late transition metal oxo complexes have been
reported.2-7 Also of interest in this regard are isolobal CR2, NR, or PR moieties stabilized
in linear Ni(II),8 trigonal Ni(II)9-12 and trigonal Ni(III) complexes.13,14 Having prepared a
number of pseudotetrahedral nickel(II) complexes supported by anionic hydrotris(pyrazol-1-yl)borates (i.e., TpNi-X),15 we noted isolobal and isoelectronic relationships to
a hypothetical oxo-Ni(II) complex supported by tris(3,5-dimethylpyrazol-1-yl)methane
(i.e., [TpmMe,MeNiII{O}]), a neutral carbon-collared Tp analog.16 Dimeric [TpNiIII(µ-O)]2
complexes have been isolated,17-21 so it seemed plausible that a monomeric TpmMe,Mesupported analog could be obtained in a pseudotetrahedral geometry and subsequently
oxidized to Ni(III) or Ni(IV) complexes stabilized by enhanced oxonickel bond order.22
Similar high-valent species have been invoked as intermediates in peroxide-driven
epoxidations and hydroxylations.23-26
We reasoned the most straightforward approach to [(TpmMe,Me)NiII(O)] or an
isolobal imido analog [(TpmMe,Me)NiII(NR)] would be addition of TpmMe,Me to
[Ni0(COD)2],27 followed by oxo atom or nitrene group transfer. Therefore, metachloroperoxybenzoic acid (mcpba), phenyl-N-tosylimidoiodinane (PhINTs; Ts = tosyl,
SO2C6H4-4-CH3) or 2-(tert-butylsulfonyl)iodosylbenzene (ArIO) were added to
[Ni0(COD)2] (COD = 1,5-cyclooctadiene) in THF in the presence of one equivalent of
157
TpmMe,Me. Our strategy was partially successful in that oxidation of [Ni0(COD)2] and
assembly of TpmMe,Me-supported nickel(II) complexes occurred readily. However, the
targeted pseudotetrahedral species were not isolated. The TpmMe,Me ligand exhibited a
marked propensity to support octahedral complexes arising from multiple ligand
additions, and the products obtained from the reagents just enumerated include
[TpmMe,MeNiII(OH2)(3-ClC6H4CO2)2] (6Ni), [(TpmMe,Me)2NiII][NiII(NHTs)4] (7Ni), and
[TpmMe,MeNiII(OH)2(OH2)] (8Ni), respectively. The syntheses and characterizations of
these novel products are described herein, which adds to the small extant body of nickeltris(pyrazolyl)methane coordination chemistry.16,28-36
Experimental
General procedures. All materials obtained from commercial vendors were ACS
reagent-grade or better and used as received, except for drying of solvents by routine
techniques. The TpmMe,Me ligand,37 phenyl-N-tosyliminoiodinane (PhINTs),38 and 2-(tertbutylsulfonyl)iodosylbenzene (ArIO)39 were prepared by literature procedures. All
manipulations were carried out under an inert atmosphere of prepurified argon, either in a
glovebox (MBraun Unilab) or using Schlenk techniques. 1H NMR data were recorded on
a Varian Unity 500 spectrometer and processed using the MestReNova 5.1 software suite
(Mestrelab Research, Santiago de Compostela, Spain); spectra were referenced internally
to the residual solvent resonance(s). UV-visible-NIR spectra were recorded on an Agilent
HP-8453 diode-array spectrophotometer. Elemental analyses were performed by Atlantic
Microlabs, Inc. (Norcross, GA).
158
Preparation of [TpmMe,MeNiII(OH2)Cl2] (5Ni).36 Anhydrous NiCl2 (195 mg, 1.50
mmol) dissolved in MeOH (15 mL) was added to a solution of TpmMe,Me (450 mg, 1.51
mmol) in CH2Cl2 (20 mL). After brief stirring, removal of solvent under vacuum gave 5Ni
as a green microcrystalline powder, which was recrystallized by slow evaporation of a
CH3CN solution. Yield: 590 mg (1.32 mmol, 88%). Anal. Calc’d. (Found) for
C16H25Cl2N6NiO1.5, 5Ni•½H2O: C, 42.23 (42.15); H, 5.54 (5.57); N, 18.47 (18.53). 1H
NMR (CD3CN, 295 K, δ ppm): 51.8 (3H, 4-H); -2.6 (9H, 5-Me); -8.7 (10H, 3-Me+CH).
1
H NMR (D2O, 295 K, δ ppm): 54.6 (3H, 4-H); -2.3 (9H, 5-Me); -8.0 (1H, CH); -10.1
(9H, 3-Me).
Preparation of [TpmMe,MeNiII(OH2)(3-ClC6H4CO2)2] (6Ni). A 1:1 mixture of mchloroperoxybenzoic acid (51.8 mg, 0.30 mmol) and m-chlorobenzoic acid (47.0 mg,
0.30 mmol) were dissolved together in THF (10 mL) and slowly added to a solution of
[Ni0(COD)2] (82.5 mg, 0.30 mmol) and TpmMe,Me (90.0 mg, 0.30 mmol) together in THF
(15 mL). The combined solutions turned light green. The solvent was stripped and the
residue was washed with Et2O. Green crystals of 6Ni•CH2Cl2•0.5C6H14 were obtained by
dissolving the remaining solids in CH2Cl2 and layering with hexanes. Yield: 106 mg
(0.13 mmol, 43% yield). Anal. Calc’d. (Found) for C30H32Cl2N6NiO5, 6Ni: C, 52.51
(53.22); H, 4.70 (4.63); N, 12.25 (11.79). 1H NMR (CD3CN, 295 K, δ ppm): 44.6 (3H, 4H); 13.9 (2H, mcba); 10.9 (2H, mcba); 9.9 (2H, mcba); 7.6 (2H, mcba); -1.2 (9H, 5-Me);
-5.6 (1H, CH); -11.9 ppm (9H, 3-Me). 1H NMR (CD2Cl2, 295 K, δ ppm): 45.8 (3H, 4-H,
species b); 43.6 (3H, 4-H, species a); 12.8 (2H, mcba, a); 10.9 (2H, mcba, a); 10.1 (sh,
2H, mcba, a); 9.5 (2H, mcba, b); 8.79 (4H, mcba, b); 7.9 (2H, mcba, a); 7.6 (2H, mcba,
159
b); -1.3 (9H, 5-Me, a); -2.2 (9H, 5-Me, b); -5.5 (1H, CH, a); -6.4 (1H, CH, b); -8.9 ppm
(9H+9H, 3-Me, a+b).
Preparation
of
[(TpmMe,Me)2NiII][NiII(NHTs)4]
(7Ni).
A 1:1
mixture of
[Ni0(COD)2] (110 mg, 0.39 mmol) and TpmMe,Me (120.0 mg, 0.40 mmol) were dissolved
together in THF (15 mL) and added slowly to a suspension of PhINTs (187 mg, 0.50
mmol) in THF (15 mL) at room temperature. The PhINTs eventually dissolved and the
solution turned purple. After stirring 20 min, a brown precipitate began to appear. After
stirring 4 h, solvent was removed under vacuum. The purple-brown solid was extracted
into CH2Cl2 (3 mL). The extracts were filtered, layered with diethyl ether and allowed to
stand at -37 °C. Purple crystals of 7Ni were isolated by filtration. Yield: 115 mg (0.08
mmol, 42 %).
Anal. Calc’d. (Found) for C60H80N16Ni2O10S4, 7Ni•2H2O:
C, 50.36
(50.53); H, 5.63 (5.55); N, 15.66 (15.48). 1H NMR (CD3CN, 295 K, δ ppm): 54.4 (6H, 4H); 10.4 (8H, Ts); 8.8 (8H, Ts); 3.7 (12H, Ts); -2.8 (18H, 5-Me); -9.8 (18 H, 3-Me); -13.9
(2H, CH), -99.4 (4H, NHTs).
Preparation of [TpmMe,MeNiII(OH)2(OH2)] (8Ni). A 1:1 mixture of [Ni0(COD)2]
(110 mg, 0.40 mmol) and TpmMe,Me (120 mg, 0.40 mmol) were dissolved together in THF
(15 mL) and slowly added to a suspension of 2-(tert-butylsulfonyl)iodosylbenzene
(153mg, 0.45 mmol) in THF (2 mL) at room temperature. The resulting pale yellowgreen solution was allowed to stir at room temperature for 4 hours. Solvent was then
stripped and the pale yellow-green solid was dissolved in a minimal amount of CH2Cl2
and layered with n-hexane. The sample was kept at -37 ºC until light purple crystals of
8Ni•CH2Cl2 formed.
Yield: 89 mg (0.18 mmol, 45%). Anal. Calc’d. (Found) for
160
C17H28Cl2N6NiO3, 8Ni•CH2Cl2: C, 41.33 (41.92); H, 5.71 (4.92); N, 17.01 (16.90).
1
H
NMR (CD3CN, 295 K, δ ppm): 54.3 (3H, 4-H); -2.8 (9H, 5-Me); -9.7 (10H, 3-Me+CH).
X-ray Crystallography. A colorless crystal of [{HC(C5H7N2)3}NiCl2(H2O)] (5Ni)
was washed with the perfluoropolyether PFO-XR75 (Lancaster) and sealed under
nitrogen in a glass capillary. The sample was optically aligned on the four-circle of a
Siemens P4 diffractometer equipped with a graphite monochromator, a monocap
collimator, a Mo Kα radiation source (λ = 0.71073 Å), and a SMART CCD detector held
at 5.082 cm from the crystal. The program SMART (version 5.6)40 was used for
diffractometer control, frame scans, indexing, orientation matrix calculations, leastsquares refinement of cell parameters, and the data collection. All 1650 crystallographic
raw data frames were read by program SAINT (version 5/6.0)41 and integrated using 3D
profiling algorithms. The resulting data were reduced to produce a total of 52862
reflections and their intensities and estimated standard deviations. A semi-empirical
absorption correction was applied using the SADABS routine available in SAINT.41,42
The data were corrected for Lorentz and polarization effects. A correction for secondary
extinction was unnecessary. No evidence of crystal decomposition was observed. Data
preparation was carried out by using the program XPREP,40 and the structure was solved
by a combination of direct methods and difference Fourier analysis with the use of
SHELXTL.43 The crystallographic asymmetric unit contains two independent molecules.
The hydrogen atoms bound to a carbon atom were included as fixed contributions using a
riding model with isotropic temperature factors set at 1.2 (methine and aromatic) or 1.5
(methyl protons) times that of the adjacent carbon atom. The positions of the hydrogen
161
atoms of the two coordinated water molecules were refined isotropically with the O-H
bond distances restrained to 0.85 ± 0.02 Å. The positions of the methyl hydrogen atoms
were optimized by a rigid rotating group refinement with idealized tetrahedral angles.
The linear absorption coefficient, atomic scattering factors, and anomalous dispersion
corrections were calculated from values found in the International Tables of X-ray
Crystallography.44 Crystal and refinement information are summarized in Appendix 36; a
thermal ellipsoid plot is shown in Figure 5.1 and relevant bond lengths and angles are
listed in the caption.
A blue crystal of [{HC(C5H7N2)3}Ni(C7H4ClO2)2(H2O)]•CH2Cl2•0.5C6H14 (6Ni)
was placed onto the tip of a 0.1 mm diameter glass capillary and mounted on a CCD area
detector diffractometer for data collection at 173(2) K.41 The data collection was carried
out using MoKα radiation (graphite monochromator) with a frame time of 15 seconds
and a detector distance of 4.9 cm. Final cell constants were calculated from strong
reflections from the actual data collection after integration (SAINT).41 The space group
P-1 was determined based on systematic absences and intensity statistics. The intensity
data were corrected for absorption and decay (SADABS).42 The structure was solved by
direct methods and refined using Bruker SHELXTL.43 All non-hydrogen atoms were
refined with anisotropic displacement parameters. All hydrogen atoms were placed in
ideal positions and refined as riding atoms with relative isotropic displacement
parameters. There was one dichloromethane per asymmetric unit that was ordered. There
was also a compositional disorder of at least two structural isomers of hexane on a
crystallographic inversion center; it appeared that n-hexane fills this site most of the time,
162
but 2-methyl-pentane was present as a substantial fraction. Attempts were made to model
this, but none was satisfactory. The disordered solvent was removed from the reported
structure by applying Platon/Squeeze.45 The ‘hexanes’ solvent filled 199.6 Å3 out of the
total 1893.3 Å3, or 10.54% of the unit cell volume. 51 electrons were found within this
space, which corresponds approximately to one solvent ‘hexanes’ molecule per unit cell.
The R1 improved from ~0.08 to 0.0495 following the application of Platon/Squeeze and
several cycles of least-squares refinement. The molecular formula is based on one hexane
per unit cell. Finally, the librational motion of the meta-chloro-benzoate group appears to
be an artifact of the hexane disorder. Crystal and refinement information are summarized
in Appendix 37; a thermal ellipsoid plot is shown in Figure 5.3 and relevant bond lengths
and angles are listed in the caption.
Violet crystals of [{HC(C5H7N2)3}2Ni][Ni(NH{SO2C6H4-4-CH3})4]•2MeCN (7Ni)
were obtained from a CD3CN solution on standing. A single crystal was selected and
placed onto the tip of a 0.1 mm diameter glass capillary and mounted on a CCD area
detector diffractometer for a data collection at 123(2) K.40 A preliminary set of cell
constants was calculated from reflections harvested from three sets of 20 frames. These
initial sets of frames were oriented such that orthogonal wedges of reciprocal space were
surveyed. This produced initial orientation matrices determined from 246 reflections. The
data collection was carried out using MoKα radiation (graphite monochromator) with a
frame time of 15 seconds and a detector distance of 4.8 cm. A randomly oriented region
of reciprocal space was surveyed to the extent of one sphere and to a resolution of 0.77
Å. Four major sections of frames were collected with 0.30º steps in ω at four different φ
163
settings and a detector position of -28º in 2θ. Final cell constants were calculated from
2969 strong reflections from the actual data collection after integration (SAINT).41 The
intensity data were corrected for absorption and decay (SADABS).42 The structure was
solved using Bruker SHELXTL43 and refined using Bruker SHELXTL.404 The space
group P21/n was determined based on systematic absences and intensity statistics. A
direct-methods solution was calculated which provided most non-hydrogen atoms from
the E-map. Full-matrix least squares / difference Fourier cycles were performed which
located the remaining non-hydrogen atoms. All non-hydrogen atoms were refined with
anisotropic displacement parameters. All hydrogen atoms were placed in ideal positions
and refined as riding atoms with relative isotropic displacement parameters. Both nickel
atoms were found on different crystallographic inversion centers. In addition, one
molecule of acetonitrile was found in a general position. In the dianion, the NHTs ligands
form a ring of four hydrogen bonds in a closed set; the two unique hydrogen atoms in
these hydrogen bonds were allowed to refine positionally with a common distance
restraint. Crystal and refinement information are summarized in Appendix 38; a thermal
ellipsoid plot is shown in Figure 5.6 and relevant bond lengths and angles are listed in the
caption.
Results and Discussion
X-ray structures were previously reported
for the sandwich dication
[(TpmMe,Me)2NiII]2+ (TpmMe,Me, tris{3,5-dimethylpyrazol-1-yl)}methane) as the bis(tetrafluoroborate),30 dibromide,31 and (NiCl4)2- salts,32 as well as the half-sandwich
complex
[TpmMe,MeNiII(κ2-NO3)(κ1-NO3)].33
Another
half-sandwich
complex
164
[TpmMe,MeNiII(OH2)Cl2] (5Ni) was previously reported, but its structure was not
determined.36 Therefore, we repeated the synthesis of 5Ni and obtained its structure
(Figure 5.1) for the purpose of comparison to analogous products obtained herein (vide
infra).
The
structure
of
5Ni
consists
of
two
independent
molecules
of
[TpmMe,MeNiII(OH2)Cl2] connected by intermolecular Cl···HO contacts in the range of
2.32(3)-2.52(3) Å, shorter than the sum of van der Waals radii. The metal-ligand bond
lengths are consistent with a d8 electron configuration (3A2g under ideal octahedral
symmetry) in which both dσ* (i.e., eg) orbitals are singly occupied. The Ni-N bonds fall
in a narrow range of 2.088(2)-2.167(2) Å; the nitrogen situated trans to the aquo ligand
exhibits a slightly shorter average bond length, 2.10(1) Å than the nitrogens trans to the
chlorides, 2.15(1) Å. The overall average Ni-N bond length of 2.13(3) Å can be
compared to an averaged value of 2.10(1) Å in various salts of [(TpmMe,Me)2NiII]2+,30-32
and a range of 2.010(3)-2.135(3) Å in [TpmMe,MeNiII(κ1-NO3)(κ2-NO3)].33 The Ni-OH2
and Ni-Cl bond lengths average 2.09(1) and 2.41(1) Å, respectively.
To further elucidate the structure of 5Ni, we define a plane that includes both
chlorides and the two trans pyrazole nitrogens (i.e., N3, N5 on Ni1 and N9, N11 on Ni2).
The nickel atoms in both molecules of 5Ni reside within 0.015 Å of the least-squares
mean. Within this “square” plane, the cis Cl-Ni-Cl bond angles are slightly opened,
93.16(2)° (Ni1) and 94.91(3)° (Ni2), while the N-Ni-N bond angles, constrained by the
bite of the TpmMe,Me chelate, are 83.06(8)° (at both Ni1 and Ni2). The cis Cl-Ni-N angles
fall in a range of 90.11(6)°-92.64(6)°; thus, the cis bond angles within the N2NiCl2 plane
165
sum to an average value of 359(1)°. The aquo ligand is essentially orthogonal to this
plane, with four cis O-Ni-N and O-Ni-Cl bond angles ranging from 88.64(8)°-91.71(5)°
with an average value of 90(1)°. However, the trans pyrazole nitrogen is also constrained
from optimal octahedral coordination by the ligand bite. The trans N-Ni-OH2 angle is
non-linear, 172.29(8)° (N1-Ni1-O1) and 173.67(8)° (N7-Ni2-O7), bending away from the
chlorides; the cis N-Ni-N and N-Ni-Cl bond angles range from 84.50(8)°-85.80(8)° and
93.44(6)°-96.42(6)°, respectively. Overall, all six cis N-Ni-N angles on the TpmMe,Me
ligand are constrained to a range of 83.06(8)-85.80(8). The trans N-Ni-Cl angles range
from 173.07(6)°-174.99(6)°. Compared to the anionic boron-collared TpMe,Me ligand,
which supports numerous 4- and 5-coordinate Ni(II) complexes with cis N-Ni-N angles
in excess of 90°,12 the constrained bite and neutral charge of the TpmMe,Me ligand appear
to favor distorted octahedral coordination. This conclusion impacted our synthetic
strategy of oxidizing [Ni0(COD)2] in the presence of TpmMe,Me with disparate oxene and
nitrene transfer reagents, which resulted in formation of a different octahedral TpmMe,Mesupported Ni(II) product complex in each case.
A 1:1 mixture of [Ni0(COD)2] and TpmMe,Me dissolved in d8-THF was examined
by 1H NMR spectroscopy at room temperature (Figure 5.2). Observed resonances were
assigned to intact [Ni0(COD)2], free TpmMe,Me and free COD. While partial solvation of
[Ni0(COD)2] was observed, no interaction with TpmMe,Me was evident. A similar result
was observed in a previous study for addition of Tpm to [Ni0(COD)2], used to promote
cross-coupling of aryl halides: Tpm was proposed to interact only with nickel(II)
generated by oxidative addition.46 We pursued a parallel strategy of adding mcbpa,
166
PhINTs or ArIO to the [Ni0(COD)2]/TpmMe,Me mixture, intending to generate
pseudotetrahedral oxene and nitrene complexes from simple atom or group transfer (i.e.,
[TpmMe,MeNiIIO]).
Addition of mcpba to the d8-THF solution of [Ni0(COD)2]/TpmMe,Me generated
multiple paramagnetic species as observed by 1H NMR spectroscopy. Co-addition of mchlorobenzoic acid gave cleaner conversion to [TpmMe,MeNiII(OH2)(3-ClC6H4CO2)2]
(6Ni). We expected that peroxidation of [Ni0(COD)2] would form [TpmMe,MeNiII(OH)(3ClC6H4CO2)] by oxidative addition (eqn. 1), with subsequent capture of the carboxylic
acid impurity giving rise to 6Ni (eqn. 2). However, 6Ni was still formed by adding the
carboxylic acid alone; hence, proton reduction by Ni(0) is competitive, leading to 6Ni by
subsequent capture of carboxylate anions and H2O (eqns. 3, 4).
L+ Ni0 + RC(O)OOH
LNiII(OH)(O2CR) + RCO 2H
LNiII(OH)(O2CR)
LNiII(OH 2)(O2 CR) 2
[1]
[2]
L+ Ni0 + 2 RC(O)OH
LNiII(O2 CR)2 + H2 O
LNiII(O2CR)2 + H2
[3]
II
LNi (OH2 )(O2CR)2
[4]
The structure of 6Ni determined by X-ray crystallography (Figure 5.3) is
analogous to that of 5Ni, with κ1-carboxylato ligands in place of the chlorides. The NiOH2 bond length in 6Ni, 2.080(2) Å is similar to that of 5Ni, as are the Ni-N bond lengths,
which range from 2.099(2)-2.153(2) Å. The Ni-N bond trans to the aquo ligand is
slightly shorter than the two Ni-N bonds disposed trans to the anionic carboxylates. The
Ni-OC(O)R bond lengths are 2.046(2) (Ni1-O1) and 2.064(2) Å (Ni1-O3). The cis N-Ni-
167
N angles average 85(2)° in 6Ni, compared to 84(1)° in 5Ni. As in the structural analysis of
5Ni, a least-squares plane can be defined by the carboxylate oxygens and trans nitrogens
(N2, N6, O1, and O3). However, the nickel atom in 6Ni is displaced 0.104 Å out of this
plane, towards the aquo ligand (O5) and away from the trans pyrazole (N4). Also unlike
5Ni, the trans N4-Ni1-O5 angle to the aquo ligand is nearly linear, 179.30(8)°, while the
trans N-Ni-O angles to the carboxylates are bent, 171.78° (N2-Ni1-O3) and 173.19(8)°
(N6-Ni1-O1). Again unable to fully span an octahedral face, the TpmMe,Me ligand is
displaced onto the N4-Ni1-OH2 axis in 6Ni, rather than into the orthogonal N2O2 plane, as
in 5Ni. This difference may reflect disparate hydrogen bonding of the aquo ligand. While
5Ni exhibits intermolecular Cl•••HO contacts, the carboxylato ligands of 6Ni support short
intramolecular hydrogen bonds between the unligated oxygens and the aquo protons,
1.82(3) Å (H5D•••O2) and 1.84(3) Å (H5E•••O4).
1
H NMR spectra of 5Ni and 6Ni in CD3CN solution are consistent with
paramagnetic (S = 1) electron configurations resulting from octahedral coordination of d8
nickel(II). The spectrum of 5Ni exhibits three signals in a 3:9:10 intensity ratio at 51.8, 2.6 and -8.7 ppm, respectively assigned to the 4-H, 5-Me, and 3-Me pyrazolyl resonances
respectively, with the latter overlapping the methine signal (Figure 5.4A). The spectrum
of 6Ni contains analogous TpmMe,Me ligand resonances at 44.6, -1.2 and -11.9 ppm, with a
resolved methine resonance at -5.6 ppm; four additional resonances at 13.9, 10.9, 9.9, and
7.6 ppm are assigned to the m-chlorophenyl substituents of the carboxylate ligands
(Figure 5.4B). The slight paramagnetic shifts indicate the carboxylates remain
coordinated to nickel(II), and the relative broadness of the two middle resonances is
168
consistent with assignment to the inequivalent ortho protons. Unlike 5Ni, complex 6Ni is
soluble in less polar solvents such as CD2Cl2, in which the spectrum exhibits a second,
somewhat broader set of resonances (labeled “b” in Figure 5.4C). This second species is
assigned as the intact complex [TpmMe,MeNiII(OH2)(3-ClC6H4CO2)2,], while the species
observed in CH3CN may result from solvation of the aquo ligand, resulting in a
dehydrated [TpmMe,MeNiII(3-ClC6H4CO2)2] derivative with at least one κ2-carboxylato
ligand.
Both 5Ni and 6Ni exhibit solution-phase UV-Vis spectra consistent with octahedral
coordination of a d8 Ni(II) ion (Figure 5).34 The spectrum of 5Ni in MeOH is very similar
to the previously reported aqueous spectrum (wherein solvolysis of the chlorides is
expected),36 with spin-allowed bands at 996 nm (3T2{F} ← 3A2) and 624 nm (3T1{F} ←
3
A2) and a spin forbidden band (1E ← 3A2) appearing as a weak shoulder at 741 nm.
Alignment on the Tanabe-Sugano diagram gives ∆O = 10,000 cm-1, B = 880 cm-1, and
places the third spin-allowed (3T1{P} ← 3A2) transition at 360 nm, where it is obscured
by the tail of strong UV bands. The spectrum of 6Ni in non-polar CH2Cl2 is modestly redshifted, consistent with its neutral charge and the spectrochemical series (ROH > RCO2-),
while a UV shoulder with partially resolved fine structure reflects the presence of the
aromatic substituents on the carboxylato ligands.
Oxidation of [Ni0(COD)2]/TpmMe,Me with a suspension of the nitrene precursor
PhINTs in THF gave a dark violet homogeneous solution that yielded a brown precipitate
on standing. This product was recrystallized and identified as [(TpmMe,Me)2NiII][NiII(NHTs)4] (7Ni). Proton reduction by [Ni(COD)2] is discounted in this reaction, since
169
the PhINTs reagent dissolved and a control mixture of 1:1:1 [Ni0(COD)2]:
TpmMe,Me:TsNH2 monitored in d8-THF by 1H NMR spectroscopy gave no evidence of
reactivity. Instead, the initial reaction of [Ni0(COD)2] and PhINTs may produce the
intended imido complex product, namely pseudotetrahedral [TpmMe,MeNiIINTs] (eqn. 5).
However, subsequent addition of free amine, initially present as an impurity in the nitrene
precursor or liberated by its hydrolysis, would form the neutral bis(amido) complex
[TpmMe,MeNiII(NHTs)2], a coordination isomer of the observed product salt (eqns. 6-8).
L+ Ni0 + PhINTs
PhINTs + H2O
LNiII(NTs) + PhI
PhIO + TsNH 2
[5]
[6]
LNiII(NTs) + TsNH2
2 LNiII(NHTs) 2
LNiII(NHTs) 2
[L2NiII][NiII(NHTs) 4]
[7]
[8]
The structure of the [(TpmMe,Me)2NiII]2+ dication determined by X-ray
crystallography is unremarkable (Figure 5.6). The pseudo-octahedral (ideally D3d) nickel
atom sits on an inversion center, so only half of the sandwich structure is unique. The
average Ni-N bond length is 2.106(6) Å and the intra- and inter-ligand cis N-Ni-N bond
angles are 85.3(6)° and 94.7(6)°, respectively, equivalent to three previous structures with
different counterions.30-32 In constrast, the square-planar [NiII(HNTs)4]2- dianion is quite
unique. A large number of Ni(II) complexes with N-substituted sulfonamidato donors
have been reported, but these are typically incorporated into chelating ligands;47-49 only
two previous examples feature primary monodentate [HNS(O)2R]- anions, and these were
neutral octahedra.50,51 The nickel atom sits on a separate inversion center. The two unique
170
Ni-N bond lengths are effectively equivalent, 1.922(2) Å (Ni2-N7) and 1.921(2) Å (Ni2N8), and the cis N-Ni-N bond angles are nearly square, 92.09(6)° (N7-Ni2-N8) and
87.91(6)° (N7-Ni2-N8′). The tosyl substituents also support a unique collar of NH•••O=S hydrogen bonds around the NiN4 plane, 2.11(2) (O2•••H8A) and 2.13(2) Å
(O3•••H7B).
The product salt 7Ni was soluble only in polar solvents. Observed paramagnetic
shifts of resonances for the [(TpmMe,Me)2NiII]2+ dication in CD3CN solution were
consistent with a previous report.31 Notwithstanding the square-planar structure observed
in the solid state, the 1H NMR resonances of the dianion were also consistent with
paramagnetism in CD3CN. The tosyl resonances (labeled “c” in Figure 5.4D) were
shifted slightly downfield (10.4, 8.8 and 3.7 ppm), while a pronounced upfield peak (at 99.4 ppm) was tentatively assigned to the amide protons. The UV-Vis-NIR spectrum in
CH3CN (Figure 5.5) appeared to be consistent with a superposition of two octahedral
species, presumably reflecting solvent coordination to the dianion. Similar to a previous
report,34 the lowest-energy ligand field transition (3T2{F} ← 3A2) of the dication
[(TpmMe,Me)2NiII]2+ was observed at 869 nm (11,500 cm-1), while the split band centered
roughly at 560 nm (17,900 cm-1) was assigned to the second ligand field band (3T1(F) ←
3
A2). A second set of bands arising from the dianion was evident, with a slight blue shift
to 759 nm (13,200 cm-1) and 442 nm (22,700 cm-1); the latter appeared to be split,
overlapping the higher energy peak of the dication as a shoulder.
No reaction was obtained from addition of insoluble PhIO to a 1:1 mixture of
[Ni0(COD)2]/TpmMe,Me in THF. However, the substituted analog 2-tBuSO2C6H4IO readily
171
dissolved and oxidized the [Ni0(COD)2]. A 1H NMR spectrum of the crude reaction
mixture extracted into CDCl3 (Figure 5.4E) revealed the presence of free COD and the
reduced aryl iodide. A major paramagnetic species was observed that exhibited
resonances similar to the other octahedral complexes already described (Figure 5.4A-C),
indicating that TpmMe,Me was bound to nickel(II) in a half-sandwich complex. Elemental
analysis of pale purple crystals isolated from the reaction mixture indicated a molecular
mass of 498(1) amu, extrapolated from the nitrogen analysis and normalized to the six
atoms of the TpmMe,Me ligand. The excess mass beyond the target complex
[TpmMe,MeNi(O)] (373 amu) was tentatively ascribed to addition of two H2O molecules
(eqns.
9-11)
and
a
lattice
CH2Cl2
molecule,
giving
a
formulation
of
[TpmMe,MeNiII(OH2)(OH)2]•CH2Cl2 (8Ni•CH2Cl2, 494 amu). Since 8Ni appears to be an
octahedral complex analogous to 5Ni or 6Ni, further structural characterization of this
product was not pursued.
L+ Ni0 + ArIO
LNiII(O) + H2O
LNiII(O) + ArI
LNiII(OH) 2
[9]
[10]
LNiII(OH)2 + H2O
LNiII(OH 2)(OH)2
[11]
The goal of this work was synthesis of hypothetical pseudotetrahedral species
[TpmMe,MeNiII=E] (E = O, NTs), by oxene atom or nitrene group transfer to
[TpmMe,MeNi0(COD)]. 1H NMR spectroscopy of a d8-THF reaction solution clearly
establishes that TpmMe,Me does not add to partial solvated [Ni0(COD)2]. Addition of
mcpba, PhINTs or ArIO results in two-electron oxidation and assembly of TpmMe,Me
172
complexes, but the reactivity does not yield the desired pseudotetrahedral products.
Instead, the TpmMe,Me ligand exhibits a marked propensity to favor octahedral nickel(II),
which seems to arise from a relatively constrained bite. This abets further addition of
fragments derived from the oxidizing precursors, either carboxylic acid, tosylamine, or
H2O, respectively. The obtained octahedral TpmMe,Me complexes, [TpmMe,MeNiII(OH2)(3ClC6H4CO2)2] (6Ni), [(TpmMe,Me)2NiII][NiII(NHTs)4] (7Ni), and [TpmMe,MeNiII(OH)2(OH2)]
(8Ni) respectively, add to the scope of nickel-tris(pyrazolyl)methane coordination
chemistry. Moreover, there is evidence that the desired oxidative oxene and nitrene
transfer chemistry may occur using hypervalent iodonium ylides. Thus, it will be worth
exploring in future work whether substitution of other oxidative substrates and
modification of the supporting scorpionate ligand would enable isolation of
pseudotetrahedral oxo and imido complexes as kinetic products of this reactivity.
173
Cl2
N1
N9
O2
Ni1
Cl1
N3
N11
Cl4
Ni2
N5
N7
O1
Cl3
Figure 5.1. Thermal ellipsoid plot (50% ellipsoids) of 5Ni. Bond lengths (Å): Ni1-N1,
2.088(2); Ni1-N3, 2.147(2); Ni1-N5, 2.167(2); Ni1-Cl1, 2.426(1); Ni1-C12, 2.420(1);
Ni1-O1, 2.078(2); C11···H2a, 2.316; C12···H2b, 2.518; Ni2-N7, 2.108(2); Ni2-N9,
2.136(2); Ni2-N11, 2.159(2); Ni2-Cl3, 2.400(1); Ni2-Cl4, 2.408(1); Ni2-O2, 2.093(2);
C13···H1a, 2.410; C14···H1b, 2.426. Bond angles (°): N1-Ni1-N3, 84.50(8); N1-Ni1-N5,
85.80(8); N1-Ni1-Cl1, 94.28(6); N1-Ni1-Cl2, 96.42(6); N3-Ni1-N5, 83.06(8); N3-Ni1O1, 89.54(8); N3-Ni1-Cl2, 92.64(6); N5-Ni1-O1, 88.64(8); N5-Ni1-Cl1, 91.17(6); O1Ni1-Cl1, 91.17(6); O1-Ni1-Cl2, 88.71(6); Cl1-Ni1-Cl2, 93.16(2); N1-Ni1-O1, 172.29(8);
N3-Ni1-Cl1, 174.17(6); N5-Ni1-Cl2, 174.97(6); N7-Ni2-N9, 84.87(8); N7-Ni2-N11,
85.49(8); N7-Ni2-Cl3, 93.44(6); N7-Ni2-Cl4, 94.29(6); N9-Ni2-N11, 83.06(8); N9-Ni2O2, 89.58(7); N9-Ni2-Cl4, 91.93(6); N11-Ni2-O2, 90.84(8); N11-Ni2-Cl3, 90.11(6); O2Ni2-Cl3, 91.71(5); O2-Ni2-Cl4, 88.92(6); Cl3-Ni2-Cl4, 94.91(3); N7-Ni2-O2, 173.67(8);
N9-Ni2-Cl3, 173.07(6); N11-Ni2-Cl4, 174.99(6).
174
(C)
s
s
(B)
(A)
10
9
8
7
6
5
4
3
2
1
0
δ (ppm)
Figure 5.2. 1H NMR spectra (d8-THF, 295 K): (A), 1:1 TpmMe,Me and [Ni0(COD)2]; (B),
free TpmMe,Me; (C), free COD. Peaks due to residual solvent are marked “s”.
175
O4
O2
O5
O3
O1
Ni1
N6
N4
N2
Figure 5.3. Thermal ellipsoid plot of 6Ni (50% probability). Bond lengths (Å): Ni1-N2,
2.129(2); Ni1-N4, 2.099(2); Ni1-N6, 2.153(2); Ni1-O1, 2.046(2); Ni1-O3, 2.064(2); Ni1O5, 2.080(2); O2··H5d, 1.823; O4··H5e, 1.838. Bond angles (°): N2-Ni1-N4, 84.25(8);
N2-Ni1-N6, 83.75(8); N2-Ni1-O1, 90.36(8); N2-Ni1-O5, 96.44(8); N4-Ni1-N6, 87.18(8);
N4-Ni1-O1, 88.83(8); N4-Ni1-O3, 88.16(8); N6-Ni1-O3, 92.75(8); N6-Ni1-O5, 92.72(8);
O1-Ni1-O3, 92.63(8); O1-Ni1-O5, 91.33(8); O3-Ni1-O5, 91.15(7); N2-Ni1-O3,
171.78(8); N4-Ni1-O5, 179.30(8); N6-Ni1-O1, 173.19(8).
176
e
~
d
ed
~~
s
(E)
c s
c
(D)
c
*
*
b
(C)
b a
a
b
s
a
b
ab
*
a+b
s
(B)
*
*
s
~
5
(A)
60
55
3
*
4
50
45
15
10
5
0
-5
-10
-15
δ (ppm)
Figure 5.4. 1H NMR spectra (295 K): (A), solvated 5Ni in wet CD3CN; (B), 6Ni in
CD3CN; (C), 6Ni in CD2Cl2; (D), 7Ni in CD3CN; (E), crude products including 8Ni from
reaction of 1:1:1 [Ni0(COD)2]:TpmMe,Me:2-tBuSO2C6H4IO in THF, extracted into CDCl3.
Peaks due to residual solvent are marked “s”; lattice solvents (CH2Cl2, hexane) are
denoted with an asterisk (*). In (A) and (E), tall peaks are truncated (~) for clarity. In (A),
pyrazole resonances of 5Ni are labeled by position. In (C), two independent sets of
resonances for 6Ni are labeled (a, b). In (D), resonances of tosyl substituents of 7Ni are
labeled (c). In (E), resonances of tBuSO2C6H4I and free COD are labeled (d) and (e),
respectively.
177
60
-1
-1
ε (M cm )
50
40
30
20
10
0
400
500
600
700
800
900
1000
λ (nm)
Figure 5.5. UV-Vis-NIR spectra (295 K) of solvated 5Ni in CH3OH (solid line), 6Ni in
CH2Cl2 (dashed line, ---) and 7Ni in CH3CN (dotted line, •••).
178
N2
N6
N7
N8
Ni2
Ni1
N2
N6
N7
N8
Figure 5.6. Thermal ellipsoid plot of 7Ni (50% probability). Hydrogen atoms omitted for
clarity, except for amides. Bond lengths (Å): Ni1-N2, 2.102(2); Ni1-N4, 2.113(1); Ni1N6, 2.102(1); Ni2-N7, 1.922(2); Ni2-N8, 1.921(2); O2•••H8A, 2.11(2); O3•••H7B,
2.13(2). Bond angles (°): N2-Ni1-N4, 85.37(5); N2-Ni1-N6, 85.94(6); N4-Ni1-N6,
84.65(5); N2-Ni1-N2′, 180; N2-Ni1-N4′, 94.63(5); N2-Ni1-N6′, 94.06(6); N4-Ni1-N4',
180; N4-Ni1-N6′, 95.35(5); N6-Ni1-N6′, 180; N7-Ni2-N8, 92.09(6); N7-Ni2-N8′,
87.91(6); N7-Ni2-N7′, 180; N8-Ni2-N8′, 180.
179
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184
APPENDIX 1: NMR SPECTRUM OF 2
2-phenyl-1-(toluene-4-sulfonyl)-aziridine1 2 (Table 3.3, entry 1)
1
H NMR (300 MHz, CDCl3): δ 7.85 (d, J = 8.1 Hz, 2H), 7.36 – 7.17 (m, 7H), 3.76 (dd, J
= 7.1, 4.5 Hz, 1H), 2.96 (d, J = 7.2 Hz, 1H), 2.41 (s, 3H), 2.37 (d, J = 4.4 Hz, 1H).
3.78
3.76
3.75
3.74
2.98
2.95
2.41
2.37
2.36
1.00
1.05
3.26
1.10
7.60
7.32
7.30
7.28
7.26
7.24
7.21
7.20
7.19
7.86
7.84
H NMR spectra for 2 (Table 3.3, entry 1)
1.99
1
185
APPENDIX 2: NMR SPECTRUM OF 52
1-(toluene-4-sulfonyl)-2-(4-trifluoromethyl-phenyl)-aziridine2 52 (Table 4.1, entry 4)
Yield: 65%; sticky solid.
1
H NMR (300 MHz, CDCl3): δ 7.85 (d, J = 8.2 Hz, 2H), 7.53 (d, J = 8.1 Hz, 2H), 7.32 (d,
J = 8.0 Hz, 4H), 3.79 (dd, J = 7.0, 4.4 Hz, 1H), 3.00 (d, J = 7.2 Hz, 1H), 2.42 (s, 3H),
2.35 (d, J = 4.3 Hz, 1H).
1
H NMR spectra for 52 (Table 4.1, entry 4)
186
APPENDIX 3: NMR SPECTRUM OF 53
2-(4-nitro-phenyl)-1-(toluene-4-sulfonyl)-aziridine1 53 (Table 4.1, entry 5)
Yield: 64%; white solid.
1
H NMR (300 MHz, CDCl3): δ 8.12 (d, J = 8.6 Hz, 2H), 7.84 (d, J = 8.2 Hz, 2H), 7.35
(dd, J = 15.4, 8.4 Hz, 4H), 3.82 (dd, J = 7.1, 4.3 Hz, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.42
(s, 3H), 2.35 (d, J = 4.2 Hz, 1H).
8.14
8.11
7.83
7.39
7.37
7.34
7.32
3.83
3.82
3.81
3.80
3.03
3.01
2.42
2.36
2.35
1.96
4.02
0.98
1.00
3.20
1.09
H NMR spectra for 53 (Table 4.1, entry 5)
1.99
1
187
APPENDIX 4: NMR SPECTRUM OF 17
3-phenyl-1-(toluene-4-sulfonyl)-aziridine-2-carboxylic acid, methyl ester1 17 (Table 3.3,
entry 6)
CO 2Me
NTs
Yield: 46%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.74 (d, J = 8.2 Hz, 2H), 7.32 – 7.17 (m, 7H), 4.41 (d, J =
3.9 Hz, 1H), 3.83 (s, 3H), 3.50 (d, J = 3.9 Hz, 1H), 2.38 (s, 3H).
7.29
7.28
7.26
7.23
4.41
4.40
3.83
3.50
3.49
2.38
7.25
0.96
2.97
0.99
3.17
7.76
7.73
H NMR spectra for 17 (Table 3.3, entry 6)
1.99
1
188
APPENDIX 5: NMR SPECTRUM OF 15
Cis-2,3-diphenyl-1-(toluene-4-sulfonyl)-aziridine1 15 (Table 3.3, entry 4)
White solid.
1
H NMR (300 MHz, CDCl3): δ 7.89 (d, J = 8.2 Hz, 2H), 7.28 (d, J = 8.2 Hz, 2H), 7.08 –
7.01 (m, 6H), 7.01 – 6.91 (m, 4H), 4.15 (s, 2H), 2.37 (s, 3H).
7.05
7.04
7.03
6.98
6.97
6.96
4.15
2.37
5.92
4.04
1.99
3.10
7.29
7.27
2.14
7.90
7.87
H NMR spectra for 15 (Table 3.3, entry 4)
1.97
1
189
APPENDIX 6: NMR Spectra OF 16
N-(1,2-diphenyl-vinyl)-4-methyl-benzenesulfonamide 16 (Table 3.3, entry 5)
Yield: 51%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.71 (d, J = 8.1 Hz, 2H), 7.38 – 7.29 (m, 5H), 7.26 – 7.18
(m, 3H), 7.09 (d, J = 7.7 Hz, 2H), 6.96 – 6.86 (m, 2H), 6.79 (d, J = 11.6 Hz, 1H), 6.26 (d,
J = 11.7 Hz, 1H), 2.44 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 144.0, 139.4, 136.8, 136.4, 129.9, 129.6, 129.4, 128.4,
128.2, 127.1, 126.8, 126.6, 126.2, 120.3, 21.6.
190
6.28
6.24
2.44
1.04
3.19
6.81
6.77
7.21
7.11
7.08
6.93
7.72
7.70
7.35
H NMR (top) and 13C NMR (bottom) spectra for 16 (Table 3.3, entry 5)
H
2.00
0.97
5.21
3.69
2.12
NHTs
1.96
1
H
NHTs
191
f1 (ppm)
COSY spectrum for 16 (Table 3.3, entry 5)
192
APPENDIX 7: NMR SPECTRUM OF 12
7-(toluene-4-sulfonyl)-7-aza-bicyclo[4.1.0]heptanes1 12 (Table 3.3, entry 2)
White solid.
1
H NMR (300 MHz, CDCl3): δ 7.84 (d, J = 8.1 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 3.00 (s,
2H), 2.46 (s, 3H), 1.81 (m, 4H), 1.42 – 1.25 (m, 4H).
2.46
3.39
4.98
3.00
2.03
1.83
1.81
1.79
1.44
1.39
1.25
7.36
7.33
2.16
4.26
7.85
7.83
H NMR spectra for 12 (Table 3.3, entry 2)
1.99
1
193
APPENDIX 8: NMR SPECTRUM OF 13
N-cyclohex-2-enyl-4-methyl-benzenesulfonamide3 13 (Table 3.3, entry 2)
White solid.
1
H NMR (300 MHz, CDCl3): δ 7.70 (d, J = 8.0 Hz, 2H), 7.23 (d, J = 7.9 Hz, 2H), 5.77 –
5.62 (m, 1H), 5.35 – 5.20 (m, 1H), 4.38 (d, J = 8.0 Hz, 1H), 3.85 – 3.64 (m, 1H), 2.36 (s,
3H), 1.91 – 1.42 (m, 6H).
5.29
5.26
4.39
4.37
3.75
2.36
0.97
0.99
1.01
3.30
1.69
1.67
1.53
1.51
1.49
5.71
5.68
1.00
1.86
7.25
7.22
2.20
6.94
7.72
7.69
H NMR spectra for 13 (Table 3.3, entry 2)
1.99
1
194
APPENDIX 9: NMR SPECTRUM OF 14
3-(toluene-4-sulfonyl)-3-aza-tricyclo[3.2.1.02,4exo]octane1 14 (Table 3.3, entry 3)
51% yield, white solid.
1
H NMR (300 MHz, CDCl3): δ 7.73 (d, J = 8.2 Hz, 2H), 7.25 (d, J = 8.1 Hz, 2H), 2.84 (s,
2H), 2.37 (s, 5H), 1.39 (m, 3H), 1.16 (m, 2H), 0.68 (d, J = 10.0 Hz, 1H).
1
H NMR spectra for 14 (Table 3.3, entry 3)
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
δ (ppm)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
195
APPENDIX 10: NMR SPECTRUM OF 32
4-methyl-N-phenyl-benzenesulfonamide4 32 (Table 3.7, entry 1)
Yield: 45%; pale pink solid.
1
H NMR (300 MHz, CDCl3): δ 7.59 (d, J = 8.0 Hz, 2H), 7.20 – 7.09 (m, 4H), 7.08 – 6.92
(m, 3H), 6.74 (br, 1H), 2.30 (s, 3H).
7.13
7.02
6.98
6.74
2.30
3.72
3.11
1.00
3.12
7.60
7.58
H NMR spectra for 32 (Table 3.7, entry 1)
1.99
1
196
APPENDIX 11: NMR SPECTRA OF 45
4-methyl-N-(2,4,6-trimethyl-phenyl)-benzenesulfonamide 45 (Table 3.7, entry 8)
Yield: 81%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.64 (d, J = 8.1 Hz, 2H), 7.27 (d, J = 8.4 Hz, 2H), 6.85 (s,
2H), 6.01 (br, 1H), 2.45 (s, 3H), 2.27 (s, 3H), 2.03 (s, 6H).
13
C NMR (75 MHz, CDCl3): δ 143.7, 138.2, 137.7, 130.2, 129.7, 127.5, 21.7, 21.1, 18.8.
197
1
H NMR (top) and 13C NMR (bottom) spectra for 45 (Table 3.7, entry 8)
198
APPENDIX 12: NMR SPECTRUM OF 39 AND 40
N-(2,5-dimethyl-phenyl)-4-methyl-benzenesulfonamide 39 and 4-methyl-N-(4-methylbenzyl)-benzenesulfonamide5 40 (Table 3.7, entry 5)
Based on 1H NMR, a mixture of aromatic and benzylic insertion product 39 and 40 was
formed in a ratio of 6.1:1; combined yield: 66%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.53 (d, J = 8.2 Hz, 2H), 7.13 (d, J = 8.2 Hz, 2H), 7.09 (s,
1H), 6.87 (d, J = 7.7 Hz, 1H), 6.80 (d, J = 7.7 Hz, 1H), 6.35 (br, 1H), 2.31 (s, 3H), 2.19
(s, 3H), 1.84 (s, 3H).
1
H NMR (300 MHz, CDCl3): δ 7.70 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.2 Hz, 2H), 7.02 (s,
4H), 4.68 (br, 1H), 4.00 (d, J = 6.1 Hz, 2H), 2.36 (s, 3H), 2.23 (s, 3H).
4.68
4.01
3.99
2.36
2.31
2.23
2.19
1.84
0.36
0.61
3.15
0.61
2.97
3.34
7.18
7.12
7.00
6.86
6.79
7.52
0.17
39
6.35
NHTs
1.00
0.42
2.09
1.08
0.75
1.07
1.07
2.12
7.71
7.68
1
0.38
199
H NMR spectra for the mixture of 39 (major) and 40 (minor) (Table 3.7, entry 5)
200
APPENDIX 13: NMR SPECTRUM OF 43 AND 44
N-(2,4-dimethyl-phenyl)-4-methyl-benzenesulfonamide 43 and N-(2,6-dimethyl-phenyl)4-methyl-benzenesulfonamide 44 (Table 3.7, entry 7)
Based on 1H NMR, a mixture of was 43 and 44 formed in a ratio of 4.9:1; combined
yield: 74%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.63 (d, J = 8.2 Hz, 2H), 7.24 (d, J = 8.1 Hz, 2H), 7.17 (d,
J = 8.0 Hz, 1H), 6.98 – 6.88 (m, 2H), 6.53 (br, 1H), 2.42 (s, 3H), 2.28 (s, 3H), 1.99 (s,
3H).
1
H NMR (300 MHz, CDCl3): δ 7.63 (d, J = 8.2 Hz, 2H), 7.24 (d, J = 8.1 Hz, 2H), 7.12 –
7.07 (m, 1H), 7.06 – 6.99 (m, 2H), 6.29 (br, 1H), 2.45 (s, 3H), 2.07 (s, 6H).
2.07
1.99
6.29
6.53
7.08
7.04
7.02
6.96
6.92
1.09
3.10
44
2.45
2.42
2.28
NHTs
0.58
2.91
2.83
0.16
1.00
2.23
1.01
0.20
0.42
2.01
7.65
7.62
7.25
1
2.28
201
H NMR spectra for the mixture of 43 (major) and 44 (minor) (Table 3.7, entry 7)
202
APPENDIX 14: NMR SPECTRUM OF 41 AND 42
N-(3,4-dimethyl-phenyl)-4-methyl-benzenesulfonamide 41 and N-(2,3-Dimethyl-phenyl)4-methyl-benzenesulfonamide 42 (Table 3.7, entry 6)
Based on 1H NMR, a mixture of 41 and 42 was formed in a ratio of 4:1; combined yield:
63%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.70 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.1 Hz, 2H), 7.07 (s,
1H), 6.98 (d, J = 8.0 Hz, 1H), 6.90 (br, 1H), 6.83 (dd, J = 8.0, 1.8 Hz, 1H), 2.39 (s, 3H),
2.18 (s, 6H).
1
H NMR (300 MHz, CDCl3): δ 7.65 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.1 Hz, 2H), 7.06 –
7.00 (m, 3H), 6.71 (br, 1H), 2.42 (s, 3H), 2.23 (s, 3H), 1.99 (s, 3H).
2.18
1.99
0.85
2.42
2.39
0.79
2.95
0.95
6.26
2.60
1.00
0.79
0.97
1.00
0.98
0.25
7.72
7.69
7.66
7.63
7.25
7.22
7.07
7.05
7.04
7.03
7.01
6.99
6.97
6.90
6.85
6.84
6.82
6.82
6.71
1
2.01
0.59
203
H NMR spectra for the mixture of 41 (major) and 42 (minor) (Table 3.7, entry 6)
204
APPENDIX 15: NMR SPECTRUM OF 37 AND 38
N-(4-isopropyl-phenyl)-4-methyl-benzenesulfonamide 37 and 4-methyl-N-(1-methyl-1phenyl-ethyl)-benzenesulfonamide3 38 (Table 3.7, entry 4)
Based on 1H NMR, a mixture of para aromatic and benzylic insertion product 37 and 38
was formed in a ratio of 1:1.1; combined yield: 57%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.50 (d, J = 8.1 Hz, 2H), 7.27 – 7.20 (m, 2H), 7.01 (d, J =
8.4 Hz, 2H), 6.90 (d, J = 8.2 Hz, 2H), 6.69 (br, 1H), 2.85 – 2.66 (m, 1H), 2.31 (s, 3H),
1.11 (d, J = 6.9 Hz, 6H).
1
H NMR (300 MHz, CDCl3): δ 7.58 (d, J = 8.2 Hz, 2H), 7.17 – 7.05 (m, 7H), 5.02 (br,
1H), 2.31 (s, 3H), 1.55 (s, 6H).
6.69
5.02
0.87
0.94
2.31
1.55
1.12
1.10
6.38
6.00
6.17
1.13
7.16
7.07
6.89
2.24
7.48
1.96
2.03
2.82
2.80
2.78
2.75
2.73
2.71
2.68
7.60
7.57
7.51
7.48
1
2.27
1.91
205
H NMR spectra for the mixture of 37 and 38 (Table 3.7, entry 4)
206
APPENDIX 16: NMR SPECTRUM OF 35 AND 36
N-(4-ethyl-phenyl)-4-methyl-benzenesulfonamide 35 and 4-methyl-N-(1-phenyl-ethyl)benzenesulfonamide5 36 (Table 3.7, entry 3)
Based on 1H NMR, a mixture of para aromatic and benzylic insertion product 35 and 36
was formed in a ratio of 1:1.1; combined yield: 62%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.68 (d, J = 8.3 Hz, 2H), 7.26 – 7.24 (m, 2H), 7.07 (d, J =
8.4 Hz, 2H), 7.01 (d, J = 8.5 Hz, 2H), 6.91 (br, 1H), 2.59 (q, J = 7.5 Hz, 2H), 2.41 (s,
3H), 1.20 (t, J = 7.6 Hz, 3H).
1
H NMR (300 MHz, CDCl3): δ 7.65 (d, J = 8.0 Hz, 2H), 7.24 – 7.19 (m, 5H), 7.13 – 7.10
(m, 2H), 5.11 (d, J = 7.0 Hz, 1H), 4.49 (p, J = 6.9 Hz, 1H), 2.41 (s, 3H), 1.45 (d, J = 6.9
Hz, 3H).
207
1
H NMR spectra for the mixture of 35 and 36 (Table 3.7, entry 3)
NHTs
36
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
δ (ppm)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
208
APPENDIX 17: NMR SPECTRUM OF 34 AND 35
4-methyl-N-p-tolyl-benzenesulfonamide6 34 and 4-methyl-N-o-tolylbenzenesulfonamide6
33 (Table 3.7, entry 2)
Based on 1H NMR, a mixture of 34 and 33 was formed in a ratio of 1.4:1; combined
yield: 60%; white solid.
1
H NMR (300 MHz, CDCl3): δ 7.54 (d, J = 8.2 Hz, 2H), 7.12 (d, J = 7.7 Hz, 2H), 6.93 (d,
J = 8.2 Hz, 2H), 6.87 (d, J = 8.4 Hz, 2H), 6.83 (br, 1H), 2.28 (s, 3H), 2.17 (s, 3H).
1
H NMR (300 MHz, CDCl3): δ 7.56 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 7.8 Hz, 1H), 7.12 (d,
J = 7.7 Hz, 2H), 7.07-6.95 (m, 3H), 6.52 (br, 1H), 2.30 (s, 3H), 1.92 (s, 3H).
2.31
2.29
2.18
1.93
3.12
4.32
4.29
3.13
1.00
1.34
5.17
3.46
5.20
1.42
7.62
7.59
7.56
7.15
7.53
7.04
7.00
6.96
6.90
6.84
6.53
1
4.90
209
H NMR spectra for the mixture of 33 and 34 (Table 3.7, entry 2)
210
APPENDIX 18: NMR SPECTRUM OF 22
N-cyclohexyl-4-methyl-benzenesulfonamide7 22 (Table 3.6, entry 1)
Yield: 40%; pale yellow solid.
1
H NMR (300 MHz, CDCl3): δ 7.69 (d, J = 8.0 Hz, 2H), 7.22 (d, J = 8.0 Hz, 2H), 4.40 (d,
J = 7.5 Hz, 1H), 3.13 – 2.96 (m, 1H), 2.35 (s, 3H), 1.74 – 1.38 (m, 5H), 1.29 – 0.98 (m,
5H).
1.26
1.19
1.14
1.11
1.08
1.05
1.01
2.35
3.45
6.85
3.07
3.06
3.04
0.93
6.64
4.41
4.39
1.00
1.56
1.53
1.46
1.43
7.23
7.21
2.21
1.70
7.70
7.68
H NMR spectra for 22 (Table 3.6, entry 1)
2.04
1
211
APPENDIX 19: NMR SPECTRUM OF 23
N-cyclopentyl-4-methyl-benzenesulfonamide7 23 (Table 3.6, entry 2)
Yield: 30%; pale yellow solid.
1
H NMR (300 MHz, CDCl3): δ 7.69 (d, J = 8.1 Hz, 2H), 7.23 (d, J = 7.9 Hz, 2H), 4.46 (d,
J = 6.9 Hz, 1H), 3.62 – 3.37 (m, 1H), 2.36 (s, 3H), 1.78 – 1.62 (m, 2H), 1.48 – 1.20 (m,
6H).
2.36
1.00
3.15
1.43
1.42
1.41
1.40
1.38
1.37
1.33
1.31
1.29
1.26
1.24
3.57
3.55
3.52
3.50
3.48
3.46
6.28
4.47
4.44
0.98
1.73
1.69
1.65
7.24
7.22
2.40
2.37
7.71
7.68
H NMR spectra for 23 (Table 3.6, entry 2)
2.25
1
212
APPENDIX 20: NMR SPECTRUM OF 19
4-methyl-N-(tetrahydrofuran-2-yl)-benzenesulfonamide3 19 (Table 3.5)
NHTs
O
1
H NMR (300 MHz, CDCl3) δ 7.83 (d, J = 8.1 Hz, 2H), 7.31 (d, J = 8.1 Hz, 2H), 5.57 (d,
J = 8.9 Hz, 1H), 5.44 – 5.29 (m, 1H), 3.78 – 3.63 (m, 2H), 2.44 (s, 3H), 2.24 – 2.07 (m,
1H), 1.99 – 1.73 (m, 3H).
3.63
2.12
2.09
1.99
1.97
1.95
1.94
1.92
1.90
1.87
1.85
1.83
1.82
1.80
1.79
1.78
1.76
1.75
2.44
2.00
2.18
3.77
3.74
3.73
3.71
3.69
3.66
5.58
5.56
5.39
5.38
5.37
5.36
5.35
5.34
7.32
7.30
7.84
7.81
H NMR spectra for 19 (Table 3.5)
3.21
1.10
0.99
0.97
2.14
with mesitylene as internal standard
2.15
1
213
APPENDIX 21: NMR SPECTRA OF 3
(2R,4S)-2,4-diphenyl-1-(toluene-4-sulfonyl)pyrrolidine8
and
(2R,4R)-2,4-diphenyl-1-
(toluene-4-sulfonyl)pyrrolidine 3 (Table 4.1, entry 1)
Based on 1H NMR, 3 was isolated as a cis and trans mixture in 1:1.1 ratio; combined
yield: 55%; sticky solid.
1
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.67 (d, J = 8.1 Hz, 2H),
7.47 – 7.21 (m, 10H), 7.16 (d, J = 7.6 Hz, 2H), 4.86 (dd, J
= 9.7, 7.1 Hz, 1H), 4.20 (dd, J = 11.2, 7.6 Hz, 1H), 3.57 (t,
J = 11.3 Hz, 1H), 2.99 (td, J = 12.0, 6.4 Hz, 1H), 2.72 (dt, J = 13.0, 6.6 Hz, 1H), 2.46 (s,
3H), 2.11 – 2.01 (m, 1H).
13
C NMR (75 MHz, CDCl3): δ 143.4, 142.5, 139.1, 135.8, 129.6, 128.7, 128.5, 127.5,
127.3, 127.2, 127.1, 126.4, 64.5, 55.9, 44.4, 42.1, 21.6.
1
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.76 (d, J = 8.1 Hz, 2H),
7.47 – 7.21 (m, 10H), 7.06 (d, J = 7.4 Hz, 2H), 5.10 (d, J =
7.9 Hz, 1H), 4.10 – 4.00 (m, 1H), 3.45 – 3.57 (m, 1H), 3.34
(t, J = 9.8 Hz, 1H), 2.48 (s, 3H), 2.27 – 2.11 (m, 2H).
13
C NMR (75 MHz, CDCl3): δ 143.5, 142.9, 139.6, 134.8, 129.7, 128.6, 128.4, 127.6,
127.2, 127.1, 127.0, 126.1, 63.1, 55.1, 43.7, 41.5, 21.5.
214
1
H and 13C NMR spectra for 3 (cis and trans diastereomer, Table 4.1, entry 1)
215
APPENDIX 22: NMR SPECTRA OF 50
1-(toluene-4-sulfonyl)-(2R,4S)-2,4-di-p-tolyl-pyrrolidine
and
1-(toluene-4-sulfonyl)-
(2R,4R)-2,4-di-p-tolyl-pyrrolidine 50 (Table 4.1, entry 2)
Based on 1H NMR, 50 was isolated as a cis and trans mixture in 1:1.2 ratio; combined
yield: 70%; sticky solid.
1
H NMR (300 MHz, CDCl3): δ 7.69 (d, J = 8.1 Hz, 2H),
7.39 – 7.07 (m, 8H), 7.05 (d, J = 8.0 Hz, 2H), 4.80 (dd, J
O
N S
O
= 9.8, 7.0 Hz, 1H), 4.17 (dd, J = 11.1, 7.5 Hz, 1H), 3.53
(t, J = 11.3 Hz, 2H), 3.03 – 2.86 (m, 1H), 2.67 (dt, J =
12.9, 6.5 Hz, 1H), 2.47 (s, 3H), 2.38 (s, 3H), 2.35 (s, 3H), 2.10 – 2.01 (m, 1H).
13
C NMR (75 MHz, CDCl3): δ 143.3, 139.6, 136.9, 136.7, 136.1, 135.8, 129.6, 129.3,
129.1, 127.5, 126.9, 126.4, 64.4, 56.0, 44.5, 42.2, 21.5, 21.1, 21.0.
1
H NMR (300 MHz, CDCl3): δ 7.77 (d, J = 8.1 Hz, 2H),
7.38 – 7.01 (m, 8H), 6.95 (d, J = 7.9 Hz, 2H), 5.05 (d, J
O
N S
O
= 8.0 Hz, 1H), 4.10 – 3.97 (m, 1H), 3.54 – 3.41 (m, 1H),
3.29 (t, J = 9.8 Hz, 1H), 2.49 (s, 3H), 2.40 (s, 3H), 2.33
(s, 3H), 2.22 – 2.09 (m, 2H).
13
C NMR (75 MHz, CDCl3): δ 143.6, 140.1, 136.8, 136.8, 136.6, 134.8, 129.7, 129.3,
129.1, 127.6, 126.9, 126.1, 62.9, 55.2, 43.3, 41.1, 21.6, 21.1, 20.9.
216
1
H and 13C NMR spectra for 50 (cis and trans diastereomer, Table 4.1, entry 2)
217
APPENDIX 23: NMR SPECTRUM OF 51
(2R, 4S)-2,4-bis-(4-chloro-phenyl)-1-(toluene-4-sulfonyl)-pyrrolidine and (2R, 4R)-2,4bis-(4-chloro-phenyl)-1-(toluene-4-sulfonyl)-pyrrolidine 51 (Table 4.1, entry 3)
Based on 1H NMR, 51 was isolated as a cis and trans mixture in 1:1 ratio; combined
yield: 69%; white solid.
Cl
1
H NMR (300 MHz, CDCl3): δ 7.65 (d, J = 8.1 Hz,
2H), 7.39 – 7.20 (m, 8H), 7.07 (d, J = 8.3 Hz, 2H),
O
N S
O
4.80 (dd, J = 9.7, 7.0 Hz, 1H), 4.16 (dd, J = 11.8, 7.4
Hz, 1H), 3.50 (t, J = 11.1 Hz, 1H), 3.06 – 2.88 (m,
Cl
1H), 2.67 (dt, J = 13.1, 6.7 Hz, 1H), 2.47 (s, 3H), 1.97 (dd, J = 22.6, 12.5 Hz, 1H).
13
C NMR (75 MHz, CDCl3): δ 143.7, 140.8, 137.9, 135.5, 133.2, 133.0, 129.7, 128.9,
128.7, 128.3, 127.8, 127.5, 63.8, 55.7, 44.3, 42.0, 21.6.
Cl
1
H NMR (300 MHz, CDCl3): δ 7.72 (d, J = 8.1 Hz,
2H), 7.38 – 7.21 (m, 8H), 6.98 (d, J = 8.3 Hz, 2H),
O
N S
O
5.02 (dd, J = 7.5, 2.1 Hz, 1H), 4.06 – 3.98 (m, 1H),
3.46 – 3.35 (m, 1H), 3.28 (t, J = 9.7 Hz, 1H), 2.48 (s,
Cl
3H), 2.13 (d, J = 7.4 Hz, 2H).
13
C NMR (75 MHz, CDCl3): δ 143.8, 141.3, 137.4, 134.5, 133.1, 132.9, 129.8, 128.8,
128.6, 128.3, 127.6, 127.5, 62.4, 55.0, 43.0, 40.9, 21.5.
218
1
H NMR spectra for 51 (cis and trans diastereomer, Table 4.1, entry 3)
219
APPENDIX 24: NMR SPECTRA OF 60
4-phenyl-1-(toluene-4-sulfonyl)-2-p-tolyl-pyrrolidine 60 (Table 4.2, entry 1)
Based on 1H NMR, 60 was isolated as a cis and trans mixture in 1.2:1 ratio; combined
yield: 80%; sticky solid.
1
H NMR (300 MHz, CDCl3): δ 7.56 (d, J = 8.1 Hz, 2H),
7.25 – 7.06 (m, 9H), 7.03 (d, J = 7.9 Hz, 2H), 4.67 (dd, J =
O
N S
O
9.8, 7.0 Hz, 1H), 4.05 (dd, J = 11.1, 7.7 Hz, 1H), 3.43 (t, J
= 11.3 Hz, 1H), 2.92 – 2.73 (m, 1H), 2.62 – 2.48 (m, 1H),
2.34 (s, 3H), 2.25 (s, 3H), 1.96 – 1.87 (m, 1H).
13
C NMR (75 MHz, CDCl3): δ 143.3, 139.6, 139.2, 137.0, 135.7, 129.6, 129.2, 128.7,
127.5, 127.1, 127.0, 126.4, 64.4, 55.9, 43.6, 41.5, 21.6, 21.2.
1
H NMR (300 MHz, CDCl3): δ 7.64 (d, J = 8.1 Hz, 2H),
7.26 – 7.06 (m, 9H), 6.93 (d, J = 6.8 Hz, 2H), 4.93 (d, J =
O
N S
O
8.0 Hz, 1H), 3.97 – 3.88 (m, 1H), 3.45 – 3.31 (m, 1H), 3.18
(t, J = 9.8 Hz, 1H), 2.35 (s, 3H), 2.26 (s, 3H), 2.11 – 1.96
(m, 2H).
13
C NMR (75 MHz, CDCl3): δ 143.5, 140.0, 139.7, 136.8, 134.7, 129.7, 129.1, 128.6,
127.6, 127.1, 127.0, 126.1, 62.9, 55.1, 44.4, 42.2, 21.6, 21.1.
220
1
H and 13C NMR spectra for 60 (cis and trans diastereomer, Table 4.2, entry 1)
221
APPENDIX 25: NMR SPECTRA OF 62
(2R, 5S)-2,5-diphenyl-3-(toluene-4-sulfonyl)-oxazolidine9 and (2R, 5R)- 2,5-diphenyl-3(toluene-4-sulfonyl)-oxazolidine 62 (Table 4.2, entry 3)
Based on 1H NMR, 62 was isolated as a cis and trans mixture in 1:1.2 ratio; combined
yield: 87%; sticky solid.
1
O
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.79 (d, J = 8.4 Hz, 2H),
7.62 (m, 2H), 7.42 – 7.24 (m, 10H), 6.35 (s, 1H), 4.54 (dd,
J = 10.1, 5.6 Hz, 1H), 4.18 (dd, J = 11.8, 5.6 Hz, 1H), 3.33
(t, 1H), 2.49 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 144.3, 138.7, 136.8, 135.5, 130.0, 129.0, 128.7, 128.6,
128.4, 127.7, 127.0, 126.3, 91.7, 79.7, 53.7, 21.6.
1
O
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.82 (d, J = 8.3 Hz, 2H),
7.69 (d, J = 6.9 Hz, 2H), 7.51 – 7.18 (m, 8H), 6.83 (d, J =
7.1 Hz, 2H), 6.61 (s, 1H), 4.99 (t, J = 7.6 Hz, 1H), 3.87
(dd, J = 10.4, 7.0 Hz, 1H), 3.39 – 3.31 (m, 1H), 2.54 (s,
3H).
13
C NMR (75 MHz, CDCl3): δ 144.3, 138.2, 137.7, 133.9, 130.0, 128.8, 128.6, 128.5,
128.4, 128.3, 126.6, 125.9, 91.5, 78.0, 53.6, 21.6.
222
1
H and 13C NMR spectra for 62 (cis and trans diastereomer, Table 4.2, entry 3)
223
APPENDIX 26: NMR SPECTRA OF 63
5-phenyl-3-(toluene-4-sulfonyl)-2-p-tolyl-oxazolidine 63 (Table 4.2, entry 4)
Based on 1H NMR, 63 was isolated as a cis and trans mixture in 1.2:1ratio; combined
yield: 90%; sticky solid.
1
H NMR (300 MHz, CDCl3): δ 7.78 (d, J = 8.2 Hz, 2H),
7.50 (d, J = 8.0 Hz, 2H), 7.41 – 7.19 (m, 9H), 6.30 (s, 1H),
O
O
N S
O
4.52 (dd, J = 10.1, 5.6 Hz, 1H), 4.16 (dd, J = 11.7, 5.6 Hz,
1H), 3.38 – 3.26 (m, 1H), 2.49 (s, 3H), 2.41 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 144.3, 138.9, 136.9, 135.8, 135.6, 130.0, 129.3, 128.6,
128.6, 127.7, 126.6, 126.3, 91.7, 79.6, 53.7, 21.6, 21.3.
1
H NMR (300 MHz, CDCl3): δ 7.81 (d, J = 8.3 Hz, 2H),
7.56 (d, J = 8.0 Hz, 2H), 7.42 – 7.20 (m, 7H), 6.82 (d, J =
O
O
N S
O
7.2 Hz, 2H), 6.57 (s, 1H), 4.98 (t, J = 7.6 Hz, 1H), 3.86
(dd, J = 10.4, 7.0 Hz, 1H), 3.38 – 3.26 (m, 1H), 2.53 (s,
3H), 2.42 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 144.3, 138.6, 137.8, 135.2, 133.9, 130.0, 129.1, 128.5,
128.3, 128.3, 126.9, 125.9, 91.54, 77.9, 53.6, 21.6, 21.2.
224
1
H and 13C NMR spectra for 63 (cis and trans diastereomer, Table 4.2, entry 4)
225
APPENDIX 27: NMR SPECTRA OF 64
2-methyl-2,5-diphenyl-3-(toluene-4-sulfonyl)-oxazolidine 64 (Table 4.2, entry 5)
Based on 1H NMR, 64 was isolated as a cis and trans mixture in 1:1ratio; combined
yield: 79%; sticky solid.
1
O
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.83 – 7.70 (m, 4H), 7.41
(m, 3H), 7.32 (m, 5H), 7.23 (m, 2H), 4.95 – 4.83 (m, 1H),
3.88 (dd, J = 9.0, 6.7 Hz, 1H), 3.50 (t, J = 8.9 Hz, 1H),
2.48 (s, 3H), 2.07 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 143.6, 143.5, 137.9, 137.4, 129.7, 128.6, 128.5, 128.4,
128.22, 127.6, 126.1, 126.0, 99.2, 75.7, 54.9, 26.5, 21.6.
1
O
O
N S
O
H NMR (300 MHz, CDCl3); δ 7.52 (d, J = 7.3 Hz, 2H),
7.48 – 7.28 (m, 6H), 7.26 – 7.23 (m, 2H), 7.05-6.98 (m,
4H), 5.43 (dd, J = 10.2, 5.4 Hz, 1H), 4.22 (dd, J = 8.7, 5.4
Hz, 1H), 3.31 – 3.19 (m, 1H), 2.35 (s, 3H), 2.26 (s, 3H).
226
1
H and 13C NMR spectra for 64 (cis and trans diastereomer, Table 4.2, entry 5)
O
O
NTs
NTs
227
APPENDIX 28: NMR SPECTRUM OF 69
2-(N-tosylamino)-1-phenyl-1-ethanol10 69 (Scheme 4.3)
White solid; hydrolysis product of 64
1
H NMR (300 MHz, CDCl3): δ 7.75 (d, J = 8.2 Hz, 2H), 7.32 (m, 7H), 5.37 – 5.20 (m,
1H), 4.82 (dd, J = 8.8, 3.4 Hz, 1H), 3.25 (ddd, J = 11.5, 7.7, 3.4 Hz, 1H), 3.04 (ddd, J =
13.1, 8.8, 4.2 Hz, 1H), 2.83 (br, 1H), 2.44 (s, 3H).
3.17
0.99
1.11
1.08
1.07
1.00
7.61
2.44
3.08
3.07
3.05
3.04
3.02
3.01
2.99
2.83
3.25
4.84
4.82
4.81
4.79
5.31
5.29
5.27
7.37
7.34
7.32
7.31
7.30
7.76
7.73
1
2.20
228
H NMR spectra for 69 (hydrolysis product of 64, Scheme 4.3)
229
APPENDIX 29: NMR SPECTRA OF 65 AND 66
3,5-diphenyl-1-(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole11 65 and 2,5-diphenyl-1(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole 66 (Table 4.2, entry 6)
Based on 1H NMR, a mixture of 65 and 66 was formed in a ratio of 1.4:1; combined
yield: 64%; sticky solid.
1
H NMR (300 MHz, CDCl3): δ 7.67-7.64 (m, 2H), 7.53 (d, J = 8.1 Hz,
2H), 7.44 – 7.42 (m, 3H), 7.24 (d, J = 7.9 Hz, 2H), 7.21 – 7.19 (m, 3H),
NTs
6.90 – 6.87 (m, 2H), 5.46 (d, J = 2.4 Hz, 1H), 4.49 (dd, J = 12.4, 9.7
Hz, 1H), 3.87 (dd, J = 12.4, 8.2 Hz, 1H), 3.77 – 3.66 (m, 1H), 2.48 (s,
3H).
13
C NMR (75 MHz, CDCl3): δ 145.9, 143.9, 142.4, 133.5, 132.7, 129.5, 129.0, 128.6,
128.1, 127.9, 127.2 126.8, 120.0, 59.8, 46.3, 21.7.
1
H NMR (300 MHz, CDCl3): δ 7.73 (d, J = 7.5 Hz, 2H), 7.61 (d, J
= 8.2 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H), 7.31 – 7.26 (m, 6H), 7.10
NTs
– 7.03 (m, 2H), 4.86 (s, 1H), 4.35 (dt, J = 8.3, 4.7 Hz, 1H), 4.23 –
4.11 (m, 2H), 2.43 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 165.5, 145.3, 142.9, 134.6, 133.0, 130.9, 129.7, 129.2,
129.1, 128.7, 128.3, 127.6, 126.4, 80.6, 67.6, 46.4, 21.7.
120.02
NTs
130.78
129.68
129.53
129.24
129.05
128.99
128.65
128.59
128.32
128.13
127.89
127.47
127.22
126.84
126.36
133.47
133.00
132.70
134.45
142.92
142.44
143.91
1
145.94
145.34
230
H and 13C NMR spectra for mixuture of 65 and 66 (Table 4.2, entry 6)
NTs
65
66
231
APPENDIX 30: NMR SPECTRA OF 67
4-methyl-3,5-diphenyl-1-(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole11 67 (Table 4.2,
entry 7)
Yield: 68%; sticky solid.
1
O
N S
O
H NMR (300 MHz, CDCl3): δ 7.45 – 7.36 (m, 4H), 7.36 –
7.25 (m, 3H), 7.17 (d, J = 8.0 Hz, 2H), 7.08 (d, J = 4.3 Hz,
3H), 6.73 – 6.62 (m, 2H), 4.27 (dd, J = 11.6, 10.6 Hz, 1H),
3.65 (dd, J = 12.1, 7.3 Hz, 1H), 3.56 (d, J = 9.3 Hz, 1H),
2.39 (s, 3H), 1.32 (s, 3H).
13
C NMR (75 MHz, CDCl3): δ 143.8, 142.2, 140.0, 133.8, 132.7, 130.0, 129.7, 128.8,
128.8, 127.8, 127.0, 126.0, 57.6, 51.9, 21.8, 12.8.
232
1
H and 13C NMR spectra for 67 (Table 4.2, entry 7)
233
APPENDIX 31
X-ray Crystallographic Data for Complex [TpmPhMn(CH3CN)3](BF4)2 (2Mn)
234
Table 1. Crystal data and structure refinement for 2Mn.
Empirical formula
C34H31B2F8MnN9
Formula weight
794.24
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
triclinic
Space group
P1
Unit cell dimensions
a = 12.6467(9) Å
α= 67.315(1)°
b = 12.9873(9) Å
β= 70.336(1)°
c = 13.4015(9) Å
γ = 73.350(1)°
Volume
1881.1(2) Å3
Z
2
Density (calculated)
1.402 g/cm3
Absorption coefficient
4.29 cm-1
F(000)
810
Crystal size
0.54 x 0.42 x 0.40 mm
θ range for data collection
2.10 to 27.56°
Index ranges
-15 ≤ h ≤ 16, -15 ≤ k ≤ 16, -17 ≤ l ≤ 17
Reflections collected
13066
Independent reflections
8270 [R(int) = 0.0340]
Completeness to θ = 27.56°
95.1 %
Max. and min. transmission
0.847 and 0.802
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
8270 / 74 / 546
Goodness-of-fit on F2
1.025
Final R indices [I>2σ(I)]
R1 = 0.0546, wR2 = 0.1524
R indices (all data)
R1 = 0.0643, wR2 = 0.1642
Largest diff. peak and hole
0.355 and -0.231 e/Å3
235
Table 2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters
(Å2 x 103) for 2Mn. U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Mn(1)
2074(1)
3991(1)
2022(1)
49(1)
N(1)
N(2)
2254(2)
2155(2)
5440(1)
6496(2)
2512(1)
1753(2)
55(1)
60(1)
N(3)
N(4)
N(5)
583(2)
746(2)
3041(2)
5335(1)
6434(1)
5008(1)
1444(1)
979(2)
299(1)
50(1)
56(1)
51(1)
N(6)
N(7)
N(8)
N(9)
2715(2)
2094(2)
3499(2)
933(2)
6158(1)
2672(2)
2900(2)
3055(2)
-6(1)
1354(2)
2768(2)
3593(2)
54(1)
63(1)
62(1)
66(1)
C(1)
C(2)
C(3)
C(4)
2566(2)
2663(3)
2394(3)
2783(2)
5560(2)
6691(2)
7254(2)
4597(2)
3319(2)
3050(2)
2060(2)
4300(2)
60(1)
80(1)
74(1)
64(1)
C(5)
C(6)
C(7)
C(8)
1966(3)
2225(4)
3261(4)
4063(3)
3937(3)
2997(3)
2738(3)
3411(3)
4986(2)
5886(3)
6090(3)
5438(3)
79(1)
98(1)
104(1)
98(1)
C(9)
C(10)
C(11)
C(12)
C(13)
3829(3)
-545(2)
-1083(2)
-248(2)
-1055(2)
4337(3)
5403(2)
6550(2)
7172(2)
4376(2)
4544(2)
1694(2)
1405(2)
962(2)
2222(2)
81(1)
55(1)
73(1)
69(1)
55(1)
C(14)
-655(2)
3498(2)
1773(2)
65(1)
C(15)
C(16)
C(17)
C(18)
-1076(2)
-1916(3)
-2346(3)
-1921(2)
2493(2)
2373(3)
3266(3)
4257(2)
2323(3)
3320(3)
3749(2)
3209(2)
79(1)
87(1)
83(1)
69(1)
236
C(19)
C(20)
3739(2)
3840(2)
4808(2)
5830(2)
-635(2)
-1525(2)
54(1)
67(1)
C(21)
C(22)
C(23)
3174(2)
4268(2)
4765(2)
6666(2)
3659(2)
2847(2)
-1100(2)
-681(2)
144(2)
65(1)
54(1)
70(1)
C(24)
C(25)
C(26)
C(27)
5212(2)
5175(3)
4699(3)
4249(2)
1754(3)
1480(3)
2277(3)
3367(2)
88(3)
-785(3)
-1619(3)
-1572(2)
85(1)
86(1)
80(1)
65(1)
C(28)
C(29)
C(30)
1849(2)
2085(2)
2045(3)
6717(2)
1874(2)
850(3)
734(2)
1213(2)
1035(3)
56(1)
63(1)
94(1)
C(31)
C(32)
C(33)
C(34)
4100(2)
4884(3)
590(2)
171(4)
2206(2)
1316(3)
2339(2)
1429(3)
3226(2)
3817(3)
4342(2)
5320(3)
62(1)
96(1)
68(1)
111(1)
B(1)
F(1)
F(2)
F(3)
3170(3)
3798(2)
2465(8)
2601(9)
9501(2)
10115(2)
10182(5)
8916(6)
3641(2)
2657(2)
4165(8)
3412(5)
71(1)
107(1)
160(4)
145(4)
F(4)
F(2')
F(3')
F(4')
B(2)
3888(5)
2079(6)
3147(10)
3570(10)
8238(4)
8768(8)
9667(14)
9765(10)
8372(4)
91(3)
4243(7)
3611(7)
4548(5)
3901(7)
1487(3)
156(5)
176(8)
130(5)
130(5)
104(1)
F(5)
F(6)
F(7)
7428(3)
9146(5)
7883(5)
548(3)
-440(6)
-777(3)
2208(3)
1935(6)
1434(4)
191(2)
217(3)
139(2)
F(8)
8483(7)
804(3)
500(5)
233(5)
F(6')
9104(8)
793(10)
1061(9)
126(5)
F(7')
8735(14)
-919(6)
1832(10)
275(18)
F(8')
7908(12)
364(16)
551(9)
282(16)
_______________________________________________________________________
237
Table 3. Selected bond lengths [Å] and angles [°] for 2Mn.
_____________________________________________________
Mn(1)-N(7)
2.209(2)
Mn(1)-N(8)
2.217(2)
Mn(1)-N(9)
2.231(2)
Mn(1)-N(5)
2.291(2)
Mn(1)-N(3)
2.292(2)
Mn(1)-N(1)
2.307(2)
N(7)-Mn(1)-N(8)
90.27(7)
N(7)-Mn(1)-N(9)
86.01(8)
N(8)-Mn(1)-N(9)
85.88(8)
N(7)-Mn(1)-N(5)
90.81(7)
N(8)-Mn(1)-N(5)
101.42(7)
N(9)-Mn(1)-N(5)
172.07(7)
N(7)-Mn(1)-N(3)
100.64(7)
N(8)-Mn(1)-N(3)
168.96(6)
N(9)-Mn(1)-N(3)
93.12(7)
N(5)-Mn(1)-N(3)
80.32(6)
N(7)-Mn(1)-N(1)
172.26(7)
N(8)-Mn(1)-N(1)
88.65(7)
N(9)-Mn(1)-N(1)
101.55(7)
N(5)-Mn(1)-N(1)
81.90(6)
N(3)-Mn(1)-N(1)
80.77(6)
C(29)-N(7)-Mn(1)
167.2(2)
C(31)-N(8)-Mn(1)
167.6(2)
C(33)-N(9)-Mn(1)
161.0(2)
_____________________________________________________
238
APPENDIX 32
X-ray Crystallographic Data for Complex [TpmPhNi(CH3CN)3](BF4)2 (2Ni)
239
Table 1. Crystal data and structure refinement for 2Ni·CH3CN.
Empirical formula
C36H34B2F8N10Ni
Formula weight
839.06
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
monoclinic
Space group
P21/n
Unit cell dimensions
a = 12.3799(8) Å
α= 90°
b = 16.6360(10) Å
β= 92.677(1)°
c = 19.5125(12) Å
γ = 90°
Volume
4014.3(4) Å3
Z
4
Density (calculated)
1.388 g/cm3
Absorption coefficient
5.61 cm-1
F(000)
1720
Crystal size
0.24 x 0.40 x 0.42 mm
θ range for data collection
1.99 to 27.52°
Index ranges
-15 ≤ h ≤ 16, -21 ≤ k ≤ 19, -24 ≤ l ≤ 25
Reflections collected
27327
Independent reflections
9148 [R(int) = 0.0448]
Completeness to θ = 27.52°
99.0 %
Max. and min. transmission
0.877 and 0.799
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
9148 / 10 / 535
Goodness-of-fit on F2
1.025
Final R indices [I>2σ(I)]
R1 = 0.0545, wR2 = 0.1545
R indices (all data)
R1 = 0.0700, wR2 = 0.1703
Largest diff. peak and hole
0.618 and -0.366 e/Å3
240
Table 2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters
(Å2 x 103) for 2Ni·CH3CN. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
_____________________________________________________________________
x
y
z
U(eq)
_____________________________________________________________________
Ni(1)
N(1)
5974(1)
6575(2)
7671(1)
8007(1)
5369(1)
4401(1)
41(1)
43(1)
N(2)
N(3)
N(4)
7150(2)
7586(2)
8112(2)
8705(1)
7871(1)
8491(1)
4407(1)
5777(1)
5473(1)
44(1)
43(1)
45(1)
N(5)
N(6)
N(7)
N(8)
5756(2)
6623(2)
5241(2)
4479(2)
8926(1)
9394(1)
7400(1)
7481(2)
5557(1)
5410(1)
6268(1)
4865(1)
42(1)
44(1)
51(1)
52(1)
N(9)
C(1)
C(2)
C(3)
6308(2)
6317(2)
6709(2)
7242(2)
6452(2)
7872(2)
8492(2)
9008(2)
5300(1)
3735(1)
3330(1)
3771(1)
56(1)
47(1)
53(1)
50(1)
C(4)
C(5)
C(6)
5735(2)
6128(2)
5621(3)
7142(2)
6380(2)
5703(2)
3481(1)
3644(2)
3375(2)
50(1)
57(1)
72(1)
C(7)
C(8)
C(9)
C(10)
C(11)
4716(3)
4329(3)
4838(3)
8375(2)
9384(2)
5781(3)
6538(3)
7211(2)
7444(2)
7787(2)
2934(2)
2768(2)
3031(2)
6100(1)
5990(2)
82(1)
84(1)
69(1)
51(1)
61(1)
C(12)
C(13)
C(14)
C(15)
C(16)
9193(2)
8170(2)
7421(3)
7270(5)
7869(7)
8450(2)
6741(2)
6779(3)
6109(5)
5439(5)
5597(1)
6537(2)
7039(2)
7463(3)
7387(4)
55(1)
65(1)
89(1)
140(3)
170(4)
C(17)
C(18)
C(19)
8631(6)
8794(4)
5158(2)
5418(4)
6060(3)
9395(2)
6903(4)
6474(3)
5955(1)
147(3)
100(1)
45(1)
241
C(20)
C(21)
5658(2)
6587(2)
10148(2)
10121(2)
6056(2)
5710(2)
58(1)
53(1)
C(22)
C(23)
C(24)
4126(2)
3291(2)
2312(2)
9156(2)
8818(2)
8643(2)
6244(1)
5844(2)
6128(2)
46(1)
56(1)
70(1)
C(25)
C(26)
C(27)
C(28)
2153(3)
2975(3)
3959(2)
7523(2)
8813(2)
9161(2)
9330(2)
9062(2)
6811(2)
7206(2)
6930(1)
5049(1)
77(1)
71(1)
59(1)
43(1)
C(29)
C(30)
C(31)
4704(2)
4014(3)
3655(2)
7203(2)
6953(3)
7369(2)
6687(2)
7231(2)
4618(2)
55(1)
87(1)
57(1)
C(32)
C(33)
C(34)
B(1)
2573(3)
6455(3)
6647(5)
1877(4)
7236(3)
5783(2)
4928(3)
5952(4)
4306(3)
5368(2)
5458(3)
6010(3)
92(1)
65(1)
113(2)
95(2)
F(1)
F(2)
F(3)
F(4)
1247(3)
2943(3)
1575(3)
1818(6)
6128(4)
6088(3)
6279(4)
5154(3)
5494(2)
5895(2)
6584(2)
6060(4)
199(2)
155(2)
213(3)
265(3)
B(2)
F(5)
F(6)
F(7)
F(8)
382(3)
-499(2)
50(6)
1114(2)
929(3)
9288(3)
9679(2)
8646(4)
9091(3)
9875(2)
4011(2)
4305(1)
3706(4)
4541(2)
3668(2)
75(1)
82(1)
234(4)
114(1)
117(1)
F(5')
F(6')
F(7')
119(11)
-580(9)
1027(18)
9403(10)
9078(13)
8655(12)
3322(5)
4210(8)
4026(14)
104(5)
129(6)
206(12)
F(8')
N(10)
C(35)
C(36)
810(30)
10646(6)
10040(7)
9354(7)
9916(13)
6664(5)
6665(5)
6691(7)
4305(15)
3202(4)
3664(6)
4234(6)
340(30)
161(3)
152(4)
217(5)
242
Table 3. Selected bond lengths [Å] and angles [°] for 2Ni·CH3CN.
_____________________________________________________
Ni(1)-N(7)
2.063(2)
Ni(1)-N(9)
2.075(3)
Ni(1)-N(8)
2.080(2)
Ni(1)-N(1)
2.136(2)
Ni(1)-N(3)
2.139(2)
Ni(1)-N(5)
2.139(2)
N(7)-Ni(1)-N(9)
86.49(10)
N(7)-Ni(1)-N(8)
87.21(9)
N(9)-Ni(1)-N(8)
89.78(10)
N(7)-Ni(1)-N(1)
173.93(8)
N(9)-Ni(1)-N(1)
96.85(9)
N(8)-Ni(1)-N(1)
87.73(8)
N(7)-Ni(1)-N(3)
99.08(8)
N(9)-Ni(1)-N(3)
89.50(9)
N(8)-Ni(1)-N(3)
173.61(9)
N(1)-Ni(1)-N(3)
86.06(8)
N(7)-Ni(1)-N(5)
90.18(9)
N(9)-Ni(1)-N(5)
172.80(8)
N(8)-Ni(1)-N(5)
96.44(9)
N(1)-Ni(1)-N(5)
87.05(8)
N(3)-Ni(1)-N(5)
84.72(8)
C(29)-N(7)-Ni(1)
168.3(2)
C(31)-N(8)-Ni(1)
177.2(3)
C(33)-N(9)-Ni(1)
169.1(2)
_____________________________________________________
243
APPENDIX 33
X-ray Crystallographic Data for Complex [TpMe,MeFe(CH3CN)3]BF4 (3Fe).
244
Table 1.Crystal data and structure refinement for 3Fe·(CH3CN)0.5.
Empirical formula
C22H32.5B2F4FeN9.5
Formula weight
583.55
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
hexagonal
Space group
R 3 (hexagonal setting)
Unit cell dimensions
a = 11.6034(6) Å
α= 90°
b = 11.6034(6) Å
β= 90°
c = 37.890(3) Å
γ = 120°
Volume
4418.0(4) Å3
Z
6
Density (calculated)
1.316 g/cm3
Absorption coefficient
5.66 cm-1
F(000)
1818
Crystal size
0.14 x 0.40 x 0.42 mm
θ range for data collection
2.10 to 27.51°
Index ranges
-15 ≤ h ≤ 14, -15 ≤ k ≤ 14, -49 ≤ l ≤ 47
Reflections collected
9721
Independent reflections
2248 [R(int) = 0.0378]
Completeness to θ = 27.51°
99.2 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
2248 / 0 / 115
Goodness-of-fit on F2
1.052
Final R indices [I>2σ(I)]
R1 = 0.0448, wR2 = 0.1352
R indices (all data)
R1 = 0.0474, wR2 = 0.1382
Largest diff. peak and hole
0.563 and -0.319 e/Å3
245
Table 2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters
(Å2 x 103) for 3Fe·(CH3CN)0.5. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Fe(1)
10000
10000
863(1)
44(1)
N(1)
8405(1)
9754(1)
1198(1)
47(1)
N(2)
8697(1)
9897(1)
1550(1)
44(1)
N(3)
8586(2)
8356(2)
511(1)
64(1)
C(1)
7208(2)
9658(2)
1165(1)
53(1)
C(2)
6739(2)
9742(2)
1494(1)
56(1)
C(3)
7697(2)
9903(2)
1734(1)
49(1)
C(4)
7698(2)
10052(2)
2124(1)
67(1)
C(5)
6562(2)
9508(3)
814(1)
75(1)
C(6)
7692(2)
7526(2)
376(1)
61(1)
C(7)
6501(3)
6460(3)
214(1)
97(1)
B(1)
10000
10000
1688(1)
44(1)
B(2)
6667
3333
256(2)
87(2)
F(1)
6667
3333
-81(2)
241(4)
F(2)
7720(2)
4490(2)
363(1)
139(1)
________________________________________________________________________
246
Table 3. Selected bond lengths [Å] and angles [°] for 3Fe·(CH3CN)0.5.
_____________________________________________________
Fe(1)-N(1)
2.1423(14)
Fe(1)-N(1)#1
2.1423(14)
Fe(1)-N(1)#2
2.1423(14)
Fe(1)-N(3)
2.232(2)
Fe(1)-N(3)#1
2.232(2)
Fe(1)-N(3)#2
2.232(2)
N(1)#1-Fe(1)-N(1)#2
88.45(5)
N(1)#1-Fe(1)-N(1)
88.45(5)
N(1)#2-Fe(1)-N(1)
88.45(5)
N(1)-Fe(1)-N(3)#2
179.26(6)
N(1)#1-Fe(1)-N(3)
179.26(6)
N(1)#2-Fe(1)-N(3)#1
179.26(6)
N(1)-Fe(1)-N(3)#1
92.26(6)
N(1)#1-Fe(1)-N(3)#2
92.26(6)
N(1)#2-Fe(1)-N(3)
92.26(6)
N(1)-Fe(1)-N(3)
91.33(6)
N(1)#1-Fe(1)-N(3)#1
91.33(6)
N(1)#2-Fe(1)-N(3)#2
91.33(6)
N(3)-Fe(1)-N(3)#1
87.96(7)
N(3)-Fe(1)-N(3)#2
87.96(7)
N(3)#1-Fe(1)-N(3)#2
87.96(7)
C(6)-N(3)-Fe(1)
166.54(19)
_____________________________________________________
247
APPENDIX 34
X-ray Crystallographic Data for Complex [TpMe,MeCo(CH3CN)3]BF4 (3Co).
248
Table 1. Crystal data and structure refinement for 3Co· (CH3CN)0.5.
Empirical formula
C22H32.5B2CoF4N9.5
Formula weight
586.63
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
hexagonal
Space group
R 3 (hexagonal setting)
Unit cell dimensions
a = 11.6161(9) Å
α= 90°
b = 11.6161(9) Å
β= 90°
c = 37.839(4) Å
γ = 120°
Volume
4421.7(7) Å3
Z
6
Density (calculated)
1.322 g/cm3
Absorption coefficient
6.36 cm-1
F(000)
1824
Crystal size
0.20 x 0.38 x 0.40 mm
θ range for data collection
2.09 to 27.51°
Index ranges
-14 ≤ h ≤ 13, -15 ≤ k ≤ 15, -48 ≤ l ≤ 45
Reflections collected
10468
Independent reflections
2260 [R(int) = 0.0610]
Completeness to θ = 27.51°
99.5 %
Max. and min. transmission
0.883 and 0.785
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
2260 / 0 / 115
Goodness-of-fit on F2
1.051
Final R indices [I>2σ(I)]
R1 = 0.0470, wR2 = 0.1385
R indices (all data)
R1 = 0.0630, wR2 = 0.1478
Largest diff. peak and hole
0.376 and -0.339 e/Å3
249
Table 2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters
(Å2 x 103) for 3Co· (CH3CN)0.5. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Co(1)
10000
0
863(1)
47(1)
N(1)
8435(2)
-224(2)
1195(1)
49(1)
N(2)
8707(2)
-91(2)
1550(1)
47(1)
N(3)
9802(2)
1394(2)
517(1)
64(1)
C(1)
7235(2)
-322(2)
1157(1)
54(1)
C(2)
6751(2)
-250(2)
1486(1)
59(1)
C(3)
7690(2)
-100(2)
1730(1)
51(1)
C(4)
7670(3)
32(3)
2120(1)
70(1)
C(5)
6610(3)
-450(4)
805(1)
78(1)
C(6)
9848(3)
2290(3)
383(1)
64(1)
C(7)
9948(4)
3470(4)
224(1)
97(1)
B(1)
10000
0
1688(1)
46(1)
B(2)
6667
3333
237(3)
98(2)
F(1)
6667
3333
-93(2)
276(5)
F(2)
7727(3)
4481(3)
349(1)
158(1)
________________________________________________________________________
250
Table 3. Selected bond lengths [Å] and angles [°] for 3Co· (CH3CN)0.5.
_____________________________________________________
Co(1)-N(1)
2.116(2)
Co(1)-N(1)#1
2.116(2)
Co(1)-N(1)#2
2.116(2)
Co(1)-N(3)
2.182(2)
Co(1)-N(3)#1
2.182(2)
Co(1)-N(3)#2
2.182(2)
N(1)#1-Co(1)-N(1)
88.35(7)
N(1)#1-Co(1)-N(1)#2
88.35(7)
N(1)-Co(1)-N(1)#2
88.35(7)
N(1)-Co(1)-N(3)#1
179.05(8)
N(1)#1-Co(1)-N(3)#2
179.05(8)
N(1)#2-Co(1)-N(3)
179.05(8)
N(1)-Co(1)-N(3)#2
91.37(8)
N(1)#2-Co(1)-N(3)#1
91.37(8)
N(1)#1-Co(1)-N(3)
91.37(8)
N(1)-Co(1)-N(3)
92.55(8)
N(1)#1-Co(1)-N(3)#1
92.55(8)
N(1)#2-Co(1)-N(3)#2
92.55(8)
N(3)#2-Co(1)-N(3)#1
87.75(9)
N(3)#2-Co(1)-N(3)
87.75(9)
N(3)#1-Co(1)-N(3)
87.75(9)
C(6)-N(3)-Co(1)
167.2(2)
__________________________________________
251
APPENDIX 35
X-ray Crystallographic Data for Complex [TpPh,MeFe(CH3CN)3]BF4 (4Fe).
252
Table 1. Crystal data and structure refinement for 4Fe·(CH3CN)0.5.
Empirical formula
C37H38.5B2F4FeN9.5
Formula weight
769.74
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
triclinic
Space group
P1
Unit cell dimensions
a = 11.5754(9) Å
α= 67.126(1)°
b = 12.2814(9) Å
β= 77.677(1)°
c = 15.4083(12) Å
γ = 76.193(1)°
Volume
1942.0(3) Å3
Z
2
Density (calculated)
1.316 g/cm3
Absorption coefficient
4.47 cm-1
F(000)
798
Crystal size
0.16 x 0.28 x 0.54 mm
θ range for data collection
1.88 to 27.60°
Index ranges
-15 ≤ h ≤ 15, -15 ≤ k ≤ 14, -18 ≤ l ≤ 20
Reflections collected
14016
Independent reflections
8709 [R(int) = 0.0339]
Completeness to θ = 27.60°
96.8 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
8709 / 22 / 549
Goodness-of-fit on F2
1.020
Final R indices [I>2σ(I)]
R1 = 0.0496, wR2 = 0.1352
R indices (all data)
R1 = 0.0665, wR2 = 0.1484
Largest diff. peak and hole
0.567 and -0.309 e/Å3
253
Table 2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters
(Å2 x 103) for 4Fe· (CH3CN)0.5. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Fe(1)
6906(1)
6212(1)
7038(1)
39(1)
N(1)
5379(2)
6736(2)
6289(1)
43(1)
N(2)
5649(2)
6694(2)
5387(1)
44(1)
N(3)
7824(2)
7476(1)
5795(1)
43(1)
N(4)
7564(2)
7539(1)
4945(1)
44(1)
N(5)
7503(2)
4827(1)
6398(1)
41(1)
N(6)
7661(2)
5328(1)
5424(1)
43(1)
N(7)
8430(2)
5403(2)
7864(2)
56(1)
N(8)
5939(2)
5049(2)
8313(1)
51(1)
N(9)
6419(2)
7584(2)
7703(1)
52(1)
C(1)
4189(2)
6811(2)
6515(2)
47(1)
C(2)
3695(2)
6821(2)
5767(2)
60(1)
C(3)
4633(2)
6743(2)
5068(2)
53(1)
C(4)
4609(3)
6721(3)
4107(2)
76(1)
C(5)
3555(2)
6875(2)
7442(2)
49(1)
C(6)
3033(2)
5921(2)
8112(2)
62(1)
C(7)
2475(3)
5972(3)
8983(2)
70(1)
C(8)
2402(3)
6977(3)
9196(2)
71(1)
C(9)
2896(3)
7932(3)
8538(2)
68(1)
C(10)
3477(2)
7874(2)
7671(2)
59(1)
C(11)
8333(2)
8442(2)
5588(2)
47(1)
C(12)
8395(2)
9106(2)
4623(2)
55(1)
C(13)
7908(2)
8518(2)
4232(2)
49(1)
C(14)
7754(3)
8816(2)
3222(2)
66(1)
C(15)
8777(2)
8701(2)
6308(2)
50(1)
C(16)
8419(3)
9828(2)
6383(2)
72(1)
C(17)
8837(3)
10068(3)
7061(3)
90(1)
C(18)
9617(3)
9221(4)
7641(3)
89(1)
C(19)
10002(3)
8144(3)
7542(3)
88(1)
254
C(20)
9576(3)
7880(2)
6886(2)
68(1)
C(21)
8206(2)
3743(2)
6621(2)
44(1)
C(22)
8837(2)
3570(2)
5795(2)
55(1)
C(23)
8474(2)
4580(2)
5054(2)
48(1)
C(24)
8862(3)
4893(2)
4005(2)
69(1)
C(25)
8211(2)
2859(2)
7601(2)
48(1)
C(26)
9267(3)
2373(2)
7994(2)
66(1)
C(27)
9285(3)
1459(3)
8876(2)
80(1)
C(28)
8268(4)
1014(2)
9356(2)
82(1)
C(29)
7219(3)
1483(2)
8980(2)
70(1)
C(30)
7171(2)
2413(2)
8105(2)
55(1)
C(31)
9198(2)
4929(2)
8293(2)
58(1)
C(32)
10200(3)
4336(4)
8837(3)
96(1)
C(33)
5476(2)
4393(2)
8959(2)
50(1)
C(34)
4873(3)
3546(2)
9781(2)
67(1)
C(35)
6227(2)
8323(2)
8003(2)
55(1)
C(36)
5951(4)
9284(3)
8389(3)
92(1)
B(1)
6956(2)
6578(2)
4904(2)
44(1)
B(2)
3030(8)
2128(8)
8905(7)
106(5)
F(1)
2593(5)
2630(7)
9560(5)
135(3)
F(2)
2197(7)
1626(9)
8775(5)
145(3)
F(3)
3303(10)
3032(5)
8120(5)
180(4)
F(4)
3986(7)
1305(7)
9219(7)
163(4)
B(2')
3127(7)
2027(8)
8700(7)
68(3)
F(1')
2717(11)
2051(12)
9575(6)
249(8)
F(2')
3098(11)
919(6)
8726(6)
152(4)
F(3')
2455(9)
2857(9)
8061(6)
171(5)
F(4')
4266(6)
2176(12)
8447(8)
190(5)
C(37)
4790(20)
-30(20)
4713(14)
95(5)
C(38)
5115(14)
174(16)
5493(11)
76(3)
N(10)
5360(7)
297(7)
6103(6)
113(2)
________________________________________________________________________
255
Table 3. Selected bond lengths [Å] and angles [°] for 4Fe· (CH3CN)0.5.
_____________________________________________________
Fe(1)-N(1)
2.150(2)
Fe(1)-N(8)
2.190(2)
Fe(1)-N(5)
2.190(2)
Fe(1)-N(3)
2.194(2)
Fe(1)-N(9)
2.202(2)
Fe(1)-N(7)
2.204(2)
N(1)-Fe(1)-N(8)
91.31(7)
N(1)-Fe(1)-N(5)
85.57(6)
N(8)-Fe(1)-N(5)
93.41(7)
N(1)-Fe(1)-N(3)
88.50(7)
N(8)-Fe(1)-N(3)
176.24(6)
N(5)-Fe(1)-N(3)
90.32(6)
N(1)-Fe(1)-N(9)
97.85(7)
N(8)-Fe(1)-N(9)
87.48(7)
N(5)-Fe(1)-N(9)
176.46(7)
N(3)-Fe(1)-N(9)
88.83(7)
N(1)-Fe(1)-N(7)
171.55(7)
N(8)-Fe(1)-N(7)
83.13(8)
N(5)-Fe(1)-N(7)
88.41(7)
N(3)-Fe(1)-N(7)
97.46(8)
N(9)-Fe(1)-N(7)
88.29(7)
C(31)-N(7)-Fe(1)
176.27(2)
C(33)-N(8)-Fe(1)
176.11(19)
C(35)-N(9)-Fe(1)
175.51(2)
_____________________________________________________
256
APPENDIX 36
X-ray Crystallographic Data for Complex [TpmMe,MeNi(OH2)Cl2] (5Ni).
257
Table 1. Crystal data and structure refinement for [TpmMe,MeNi(OH2)Cl2] (5Ni).
Empirical formula
C16 H24 Cl2 N6 Ni O
Formula weight
446.02
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system
Orthorhombic
Space group
Pbca
Unit cell dimensions
a = 15.8781(9) Å
α= 90°.
b = 13.9478(8) Å
β= 90°.
c = 35.968(2) Å
γ = 90°.
Volume
7965.6(8) Å3
Z
16
Density (calculated)
1.488 Mg/m3
Absorption coefficient
1.260 mm-1
F(000)
3712
Crystal size
0.40 x 0.24 x 0.10 mm3
Theta range for data collection
2.02 to 27.52°.
Index ranges
-20<=h<=20, -18<=k<=15, -46<=l<=46
Reflections collected
52862
Independent reflections
9092 [R(int) = 0.0593]
Completeness to theta = 27.52°
99.1 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
9092 / 4 / 497
Goodness-of-fit on F2
1.025
Final R indices [I>2sigma(I)]
R1 = 0.0405, wR2 = 0.0997
R indices (all data)
R1 = 0.0574, wR2 = 0.1110
Largest diff. peak and hole
0.620 and -0.436 e.Å-3
258
Table 2. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters
(Å2x 103) for 5Ni. U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Ni(1)
5230(1)
9310(1)
1944(1)
31(1)
Ni(2)
4685(1)
7710(1)
634(1)
32(1)
Cl(1)
6453(1)
9171(1)
1543(1)
42(1)
Cl(2)
4487(1)
10336(1)
1512(1)
41(1)
Cl(3)
5336(1)
6675(1)
1084(1)
41(1)
Cl(4)
3441(1)
7996(1)
1000(1)
43(1)
N(1)
5745(1)
10410(1)
2266(1)
37(1)
N(2)
5750(1)
10290(1)
2644(1)
36(1)
N(3)
4220(1)
9353(1)
2341(1)
35(1)
N(4)
4433(1)
9473(2)
2709(1)
39(1)
N(5)
5788(1)
8344(1)
2347(1)
35(1)
N(6)
5710(1)
8592(1)
2715(1)
36(1)
N(7)
4151(1)
6561(1)
335(1)
37(1)
N(8)
4282(1)
6532(1)
-41(1)
39(1)
N(9)
4224(1)
8578(1)
190(1)
36(1)
N(10)
4280(1)
8214(1)
-164(1)
38(1)
N(11)
5755(1)
7536(2)
270(1)
38(1)
N(12)
5581(1)
7384(2)
-97(1)
40(1)
O(1)
4668(1)
8132(1)
1692(1)
37(1)
O(2)
5234(1)
8926(1)
875(1)
38(1)
C(1)
6183(2)
11211(2)
2204(1)
41(1)
C(2)
6466(2)
11588(2)
2543(1)
47(1)
C(3)
6192(2)
10996(2)
2819(1)
39(1)
C(4)
6314(2)
11595(2)
1823(1)
57(1)
C(5)
6315(2)
11028(2)
3230(1)
50(1)
259
C(6)
3390(2)
9250(2)
2341(1)
38(1)
C(7)
3069(2)
9282(2)
2707(1)
43(1)
C(8)
3744(2)
9412(2)
2935(1)
41(1)
C(9)
2901(2)
9099(2)
1990(1)
48(1)
C(10)
3790(2)
9488(2)
3350(1)
52(1)
C(11)
6088(2)
7453(2)
2350(1)
41(1)
C(12)
6188(2)
7127(2)
2716(1)
51(1)
C(13)
5942(2)
7861(2)
2944(1)
43(1)
C(14)
6276(2)
6918(2)
2003(1)
56(1)
C(15)
5942(2)
7926(2)
3359(1)
61(1)
C(16)
5311(2)
9493(2)
2809(1)
36(1)
C(17)
3731(2)
5757(2)
415(1)
44(1)
C(18)
3605(2)
5222(2)
89(1)
53(1)
C(19)
3965(2)
5722(2)
-199(1)
46(1)
C(20)
3466(2)
5522(2)
802(1)
59(1)
C(21)
4029(2)
5492(2)
-603(1)
66(1)
C(22)
3894(2)
9450(2)
147(1)
41(1)
C(23)
3744(2)
9633(2)
-231(1)
51(1)
C(24)
3999(2)
8846(2)
-425(1)
42(1)
C(25)
3745(2)
10106(2)
466(1)
53(1)
C(26)
4017(2)
8657(2)
-834(1)
56(1)
C(27)
6594(2)
7583(2)
288(1)
41(1)
C(28)
6948(2)
7468(2)
-67(1)
46(1)
C(29)
6292(2)
7352(2)
-309(1)
42(1)
C(30)
7046(2)
7745(2)
646(1)
60(1)
C(31)
6273(2)
7243(2)
-722(1)
60(1)
C(32)
4716(2)
7315(2)
-220(1)
38(1)
________________________________________________________________________
260
Table 3. Selected bond lengths [Å] and angles [°] for 5Ni.
_____________________________________________________
Ni(1)-O(1)
2.0776(17)
Ni(1)-N(1)
2.088(2)
Ni(1)-N(3)
2.147(2)
Ni(1)-N(5)
2.167(2)
Ni(1)-Cl(2)
2.4202(7)
Ni(1)-Cl(1)
2.4264(7)
Ni(2)-O(2)
2.0932(18)
Ni(2)-N(7)
2.108(2)
Ni(2)-N(9)
2.136(2)
Ni(2)-N(11)
2.159(2)
Ni(2)-Cl(3)
2.4004(7)
Ni(2)-Cl(4)
2.4077(7)
O(1)-Ni(1)-N(1)
172.29(8)
O(1)-Ni(1)-N(3)
89.54(8)
N(1)-Ni(1)-N(3)
84.50(8)
O(1)-Ni(1)-N(5)
88.64(8)
N(1)-Ni(1)-N(5)
85.80(8)
N(3)-Ni(1)-N(5)
83.06(8)
O(1)-Ni(1)-Cl(2)
88.71(6)
N(1)-Ni(1)-Cl(2)
96.42(6)
N(3)-Ni(1)-Cl(2)
92.64(6)
N(5)-Ni(1)-Cl(2)
174.97(6)
O(1)-Ni(1)-Cl(1)
91.17(6)
N(1)-Ni(1)-Cl(1)
94.28(6)
N(3)-Ni(1)-Cl(1)
174.17(6)
N(5)-Ni(1)-Cl(1)
91.17(6)
Cl(2)-Ni(1)-Cl(1)
93.16(2)
O(2)-Ni(2)-N(7)
173.67(8)
261
O(2)-Ni(2)-N(9)
89.58(7)
N(7)-Ni(2)-N(9)
84.87(8)
O(2)-Ni(2)-N(11)
90.84(8)
N(7)-Ni(2)-N(11)
85.49(8)
N(9)-Ni(2)-N(11)
83.06(8)
O(2)-Ni(2)-Cl(3)
91.71(5)
N(7)-Ni(2)-Cl(3)
93.44(6)
N(9)-Ni(2)-Cl(3)
173.07(6)
N(11)-Ni(2)-Cl(3)
90.11(6)
O(2)-Ni(2)-Cl(4)
88.92(6)
N(7)-Ni(2)-Cl(4)
94.29(6)
N(9)-Ni(2)-Cl(4)
91.93(6)
N(11)-Ni(2)-Cl(4)
174.99(6)
Cl(3)-Ni(2)-Cl(4)
94.91(3)
_____________________________________________________
262
APPENDIX 37
X-ray Crystallographic Data for Complex [TpmMe,MeNi(OH2)(m-ClC6H4CO2)2] (6Ni)
263
Table 1. Crystal data and structure refinement for 6Ni· CH2Cl2· 0.5C6H14.
Empirical formula
C34H41Cl4N6NiO5
Formula weight
814.24
Temperature
173(2) K
Wavelength
0.71073 Å
Crystal system
Triclinic
Space group
P-1
Unit cell dimensions
a = 10.1691(12) Å
α= 98.767(2)°.
b = 12.2478(14) Å
β= 91.705(2)°.
c = 15.6803(18) Å
γ = 100.682(2)°.
Volume
1893.3(4) Å3
Z
2
Density (calculated)
1.428 Mg/m3
Absorption coefficient
0.843 mm-1
F(000)
846
Crystal size
0.45 x 0.18 x 0.15 mm3
Theta range for data collection
1.71 to 27.53°.
Index ranges
-13<=h<=13, -15<=k<=15, 0<=l<=20
Reflections collected
21539
Independent reflections
8523 [R(int) = 0.0309]
Completeness to theta = 27.53°
97.7 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
8523 / 2 / 436
Goodness-of-fit on F2
1.084
Final R indices [I>2sigma(I)]
R1 = 0.0495, wR2 = 0.1262
R indices (all data)
R1 = 0.0649, wR2 = 0.1341
Largest diff. peak and hole
1.840 and -1.886 e.Å-3
264
Table 2. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters
(Å2x 103) for 6Ni· CH2Cl2· 0.5C6H14. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Ni(1)
6505(1)
1659(1)
2228(1)
21(1)
C(1)
3400(2)
1303(2)
2059(2)
23(1)
N(1)
3881(2)
1353(2)
1206(1)
24(1)
N(2)
5234(2)
1518(2)
1097(1)
23(1)
C(2)
3149(3)
1208(2)
439(2)
27(1)
C(3)
4068(3)
1296(2)
-179(2)
30(1)
C(4)
5342(3)
1493(2)
251(2)
24(1)
C(5)
1656(3)
975(3)
365(2)
38(1)
C(6)
6665(3)
1679(3)
-136(2)
32(1)
N(3)
3892(2)
2329(2)
2644(1)
22(1)
N(4)
5248(2)
2706(2)
2799(1)
23(1)
C(7)
3176(3)
3054(2)
3070(2)
28(1)
C(8)
4101(3)
3923(2)
3508(2)
33(1)
C(9)
5374(3)
3689(2)
3323(2)
26(1)
C(10)
1679(3)
2818(3)
3020(2)
43(1)
C(11)
6711(3)
4388(2)
3629(2)
33(1)
N(5)
3725(2)
336(2)
2384(1)
24(1)
N(6)
5046(2)
257(2)
2494(1)
23(1)
C(12)
2875(3)
-605(2)
2529(2)
27(1)
C(13)
3677(3)
-1317(2)
2743(2)
31(1)
C(14)
5012(3)
-758(2)
2714(2)
28(1)
C(15)
1389(3)
-725(3)
2464(2)
41(1)
C(16)
6258(3)
-1177(3)
2902(2)
37(1)
O(1)
7708(2)
3048(2)
1901(1)
29(1)
265
O(2)
9413(2)
2366(2)
1279(1)
38(1)
C(17)
8807(3)
3147(2)
1537(2)
28(1)
C(18)
9418(3)
4313(2)
1384(2)
29(1)
C(19)
8691(3)
5176(2)
1512(2)
30(1)
C(20)
9247(3)
6221(2)
1322(2)
35(1)
Cl(1)
8320(1)
7292(1)
1455(1)
52(1)
C(21)
10505(4)
6443(3)
1023(2)
47(1)
C(22)
11232(3)
5591(3)
908(2)
50(1)
C(23)
10699(3)
4532(3)
1079(2)
41(1)
O(3)
7510(2)
1857(2)
3421(1)
29(1)
O(4)
9032(2)
746(2)
3191(1)
36(1)
C(24)
8515(3)
1466(2)
3647(2)
28(1)
C(25)
9139(3)
1919(2)
4544(2)
30(1)
C(26)
8733(4)
2806(3)
5049(2)
50(1)
C(27)
9338(4)
3216(3)
5870(2)
55(1)
Cl(2)
8757(2)
4285(1)
6530(1)
143(1)
C(28)
10355(4)
2775(3)
6187(2)
51(1)
C(29)
10737(4)
1890(5)
5693(2)
77(2)
C(30)
10140(4)
1462(4)
4878(2)
60(1)
O(5)
7760(2)
620(2)
1677(1)
28(1)
C(31)
5212(4)
1722(3)
4897(2)
56(1)
Cl(3)
3622(1)
884(1)
4605(1)
67(1)
Cl(4)
5107(2)
3021(1)
5519(1)
76(1)
________________________________________________________________________
266
Table 3. Selected bond lengths [Å] and angles [°] for 6Ni· CH2Cl2· 0.5C6H14.
_____________________________________________________
Ni(1)-O(1)
2.0461(18)
Ni(1)-O(3)
2.0639(18)
Ni(1)-O(5)
2.0795(19)
Ni(1)-N(4)
2.099(2)
Ni(1)-N(2)
2.129(2)
Ni(1)-N(6)
2.153(2)
O(1)-Ni(1)-O(3)
92.63(8)
O(1)-Ni(1)-O(5)
91.33(8)
O(3)-Ni(1)-O(5)
91.15(7)
O(1)-Ni(1)-N(4)
88.83(8)
O(3)-Ni(1)-N(4)
88.16(8)
O(5)-Ni(1)-N(4)
179.30(8)
O(1)-Ni(1)-N(2)
90.36(8)
O(3)-Ni(1)-N(2)
171.78(8)
O(5)-Ni(1)-N(2)
96.44(8)
N(4)-Ni(1)-N(2)
84.25(8)
O(1)-Ni(1)-N(6)
173.19(8)
O(3)-Ni(1)-N(6)
92.75(8)
O(5)-Ni(1)-N(6)
92.72(8)
N(4)-Ni(1)-N(6)
87.18(8)
N(2)-Ni(1)-N(6)
83.75(8)
_____________________________________________________
267
Table 4. Hydrogen bonds for 6Ni· CH2Cl2· 0.5C6H14 [Å and °].
________________________________________________________________________
D-H...A
d(D-H)
d(H...A)
d(D...A)
<(DHA)
________________________________________________________________________
O(5)-H(5D)...O(2)
0.834(18)
1.82(2)
2.632(3)
163(4)
O(5)-H(5E)...O(4)
0.824(18)
1.84(2)
2.638(3)
164(4)
________________________________________________________________________
268
APPENDIX 38
X-ray Crystallographic Data for Complex [(TpmMe,Me)2Ni][Ni(NHTs)4] (7Ni)
269
Table 1. Crystal data and structure refinement for 7Ni · 2CH3CN.
Empirical formula
C64H82N18Ni2O8S4
Formula weight
1477.14
Temperature
123(2) K
Wavelength
0.71073 Å
Crystal system
Monoclinic
Space group
P2(1)/n
Unit cell dimensions
a = 11.9729(12) Å
α= 90°.
b = 18.5906(19) Å
β= 101.162(1)°.
c = 15.7359(16) Å
γ = 90°.
Volume
3436.3(6) Å3
Z
2
Density (calculated)
1.428 Mg/m3
Absorption coefficient
0.737 mm-1
F(000)
1552
Crystal size
0.50 x 0.50 x 0.15 mm3
Theta range for data collection
1.71 to 27.49°.
Index ranges
-15<=h<=15, 0<=k<=24, 0<=l<=20
Reflections collected
40943
Independent reflections
7871 [R(int) = 0.0319]
Completeness to theta = 27.49°
99.7 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
7871 / 1 / 451
Goodness-of-fit on F2
1.066
Final R indices [I>2sigma(I)]
R1 = 0.0315, wR2 = 0.0790
R indices (all data)
R1 = 0.0431, wR2 = 0.0873
Largest diff. peak and hole
0.520 and -0.370 e.Å-3
270
Table 2. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters
(Å2x 103) for 7Ni· 2CH3CN. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x
y
z
U(eq)
________________________________________________________________________
Ni(1)
5000
5000
10000
14(1)
N(1)
4872(1)
4766(1)
8104(1)
17(1)
N(2)
5622(1)
4964(1)
8840(1)
17(1)
N(3)
3537(1)
4062(1)
8687(1)
16(1)
N(4)
4095(1)
4058(1)
9538(1)
16(1)
N(5)
3212(1)
5315(1)
8440(1)
17(1)
N(6)
3588(1)
5542(1)
9278(1)
16(1)
C(1)
5380(2)
4718(1)
7402(1)
20(1)
C(2)
6505(2)
4886(1)
7703(1)
22(1)
C(3)
6619(2)
5037(1)
8592(1)
19(1)
C(4)
4756(2)
4524(1)
6517(1)
30(1)
C(5)
7670(2)
5261(1)
9210(1)
23(1)
C(6)
2877(1)
3464(1)
8481(1)
18(1)
C(7)
3018(2)
3063(1)
9229(1)
20(1)
C(8)
3779(1)
3445(1)
9865(1)
17(1)
C(9)
2179(2)
3331(1)
7599(1)
24(1)
C(10)
4218(2)
3228(1)
10786(1)
21(1)
C(11)
2386(2)
5750(1)
7997(1)
20(1)
C(12)
2213(2)
6272(1)
8577(1)
23(1)
C(13)
2969(2)
6128(1)
9359(1)
19(1)
C(14)
1877(2)
5648(1)
7062(1)
28(1)
C(15)
3108(2)
6542(1)
10187(1)
23(1)
C(16)
3685(1)
4668(1)
8142(1)
16(1)
Ni(2)
0
5000
5000
15(1)
271
N(7)
979(1)
5811(1)
4942(1)
19(1)
S(1)
1959(1)
5961(1)
4428(1)
17(1)
O(1)
2453(1)
6668(1)
4638(1)
24(1)
O(2)
2761(1)
5364(1)
4534(1)
24(1)
C(17)
1358(2)
6001(1)
3302(1)
19(1)
C(18)
706(2)
5430(1)
2908(1)
24(1)
C(19)
248(2)
5459(1)
2029(1)
29(1)
C(20)
429(2)
6053(1)
1531(1)
31(1)
C(21)
1084(2)
6616(1)
1936(1)
32(1)
C(22)
1547(2)
6597(1)
2817(1)
28(1)
C(23)
-81(2)
6091(2)
578(1)
44(1)
N(8)
-1344(1)
5583(1)
4707(1)
20(1)
S(2)
-1593(1)
6405(1)
4838(1)
17(1)
O(3)
-821(1)
6846(1)
4458(1)
22(1)
O(4)
-2800(1)
6554(1)
4558(1)
24(1)
C(24)
-1282(2)
6626(1)
5964(1)
18(1)
C(25)
-394(2)
7089(1)
6287(1)
22(1)
C(26)
-208(2)
7300(1)
7150(1)
26(1)
C(27)
-895(2)
7055(1)
7704(1)
28(1)
C(28)
-1768(2)
6576(1)
7377(1)
29(1)
C(29)
-1964(2)
6359(1)
6517(1)
25(1)
C(30)
-700(2)
7307(2)
8635(1)
42(1)
N(9)
4513(2)
6490(2)
7082(2)
64(1)
C(31)
4758(2)
6496(1)
6427(2)
37(1)
C(32)
5062(2)
6483(2)
5582(2)
58(1)
________________________________________________________________________
272
Table 3. Selected bond lengths [Å] and angles [°] for 7Ni· 2CH3CN.
_____________________________________________________
Ni(1)-N(2)
2.1017(15)
Ni(1)-N(2)#1
2.1017(15)
Ni(1)-N(6)#1
2.1022(14)
Ni(1)-N(6)
2.1022(14)
Ni(1)-N(4)#1
2.1129(14)
Ni(1)-N(4)
2.1129(14)
Ni(2)-N(8)#2
1.9205(15)
Ni(2)-N(8)
1.9205(15)
Ni(2)-N(7)
1.9222(15)
Ni(2)-N(7)#2
1.9222(15)
N(2)-Ni(1)-N(2)#1
180.000(1)
N(2)-Ni(1)-N(6)#1
94.06(6)
N(2)#1-Ni(1)-N(6)#1
85.94(6)
N(2)-Ni(1)-N(6)
85.94(6)
N(2)#1-Ni(1)-N(6)
94.06(6)
N(6)#1-Ni(1)-N(6)
180.0
N(2)-Ni(1)-N(4)#1
94.63(5)
N(2)#1-Ni(1)-N(4)#1
85.37(5)
N(6)#1-Ni(1)-N(4)#1
84.65(5)
N(6)-Ni(1)-N(4)#1
95.35(5)
N(2)-Ni(1)-N(4)
85.37(5)
N(2)#1-Ni(1)-N(4)
94.63(5)
N(6)#1-Ni(1)-N(4)
95.35(5)
N(6)-Ni(1)-N(4)
84.65(5)
N(4)#1-Ni(1)-N(4)
180.0
N(8)#2-Ni(2)-N(8)
180.00(9)
N(8)#2-Ni(2)-N(7)
87.91(6)
N(8)-Ni(2)-N(7)
92.09(6)
N(8)#2-Ni(2)-N(7)#2
92.09(6)
N(8)-Ni(2)-N(7)#2
87.91(6)
N(7)-Ni(2)-N(7)#2
180.0
_____________________________________________________
273
Table 4. Hydrogen bonds for 7Ni· 2CH3CN [Å and °].
_________________________________________________________________
D-H...A
d(D-H)
d(H...A)
d(D...A)
<(DHA)
_________________________________________________________________
N(7)-H(7B)...O(3)
0.811(17)
2.130(18)
2.881(2)
154(2)
N(8)-H(8A)...O(2)#2
0.811(17)
2.112(18)
2.863(2)
154(2)
_________________________________________________________________
Symmetry transformations used to generate equivalent atoms:
#1 -x+1,-y+1,-z+2
#2 -x,-y+1,-z+1
274
Reference
(1) Evens, D. A.; Faul, M. M.; Bilodeau, M. T. J. Am. Chem. Soc. 1994, 116, 27422753.
(2) Gao, G. Y.; Harden, J. D.; Zhang, X. P. Org. Lett. 2005, 7, 3191-3193.
(3) Bhuyan, R.; Nicholas, K. M. Org. Lett. 2007, 9, 3957-3959.
(4) Zheng, Z. G.; Wen, J.; Wang, N.; Wu, B.; Yu, X. Q. Beilstein J. Org. Chem. 2008, 4.
(5) Cui, X. J.; Shi, F.; Tse, M. K.; Gordes, D.; Thurow, K.; Beller, M.; Deng, Y. Q.
Adv. Synth. Catal. 2009, 351, 2949-2958.
(6) Shekhar, S.; Dunn, T. B.; Kotecki, B. J.; Montavon, D. K.; Cullen, S. C. J. Org.
Chem. 2011, 76, 4552-4563.
(7) Zhu, M. W.; Fujita, K.; Yamaguchi, R. Org. Lett. 2010, 12, 1336-1339.
(8) Kelleher, S.; Quesne, P. Y.; Evans, P. Beilstein J. Org. Chem. 2009, 5.
(9) Gandhi, S.; Bisai, A.; Prasad, B. A. B.; Singh, V. K. J. Org. Chem. 2007, 72, 21332142.
(10) Ghorai, M. K.; Ghosh, K. Tetrahedron Lett. 2007, 48, 3191-3195.
(11) Wender, P. A.; Strand, D. J. Am. Chem. Soc. 2009, 131, 7528-7529.
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