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NICKEL(II) PINCER COMPLEXES SUPPORTED BY 2,6-BIS(3,5-DITOLYL-2PYRROLYL)PYRIDINE
by
ABHIJIT PRAMANIK
Presented to the Faculty of the Graduate School of
The University of Texas at Arlington in Partial Fulfillment
of the Requirements
for the Degree of
MASTER OF SCIENCE IN CHEMISTRY
THE UNIVERSITY OF TEXAS AT ARLINGTON
May 2015
Copyright © by Abhijit Pramanik 2015
All Rights Reserved
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Acknowledgements
I would like to acknowledge the contribution of the following persons to
the fulfillment of this thesis work.
I am specially thankful to my supervising professor Dr. H. V. Rasika Dias for his guidance
and encouragement through my graduate study at UT Arlington. I also would like to thank
the other committee members, Dr. Alejandro Bugarin and Dr. Brad Pierce for their
support. I am thankful to Dr. Muhammed Yousufuddin for his Xray crystallography work.
I appreciate the immense help I received from all other past and
present Dias research group members. I would like to mention the names of some lab
members like Dr. Chandrakanta Dash, Dr. Animesh Das, Dr. Naveen Kulkarni, Mr.
Venkata K. Adiraju, Mr. Naleen Jayaratna for their assistance in learning the theoretical
and technical skills needed for my research.
Finally, I would also like to thank the Department of Chemistry and
Biochemistry of The University of Texas at Arlington, the Robert A. Welch Foundation
and National Science Foundation for their financial support.
April 14, 2015
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Abstract
NICKEL(II) PINCER COMPLEXES SUPPORTED BY 2,6-BIS(3,5-DITOLYL-2PYRROLYL)PYRIDINE
Abhijit Pramanik, MS
The University of Texas at Arlington, 2015
Supervising Professor: H. V. Rasika Dias
Ni(II) pincer complexes are among the most important and useful
compounds in homogeneous catalysis. Significant advancement has been made in this
field in recent years. Many Ni(II) pincer complexes have been prepared and utilized in
various catalytic reactions e.g. cross coupling reactions, C-H activation, carbon dioxide
activation etc. Still, nickel(II) complexes supported by the pincer ligand with three nitrogen
donors are relatively less explored and catalytic applications with those complexes are
scarce in literature.
This thesis describes the synthesis of a new pyrrolyl pyridine based
pincer ligand and its Ni(II) complexes. The pyrrolyl pyridine pincer ligand, a relatively new
class of dianionic, tridentate, nitrogen-based ligands in coordination chemistry, was
prepared starting with a modified method for the synthesis of pyrrolyl pyridine. This
modified procedure is simpler, less time consuming making it cheaper than the classical
method and provides 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine in good yields. Reaction of its
potassium salt with Ni(OTf)2 resulted in three different stable nickel(II) pincer complexes.
1
The novel nickel(II) pincer complexes were fully characterized by H NMR spectroscopy,
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C NMR spectroscopy, infrared spectroscopy and high resolution mass spectrometry.
The X-ray crystal structures of the new ligand and metal complexes have been
described.
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Table of Contents
Acknowledgements .............................................................................................................iii
Abstract .............................................................................................................................. iv
List of Illustrations ..............................................................................................................vii
List of Tables………………………………………………………………………………...……ix
Chapter 1 NNN pincer ligand………………………………………………………..………….1
1.1 Introduction………………………………………………………………………………..1
1.1.1. Importance of pincer ligands……………………………………………………….1
1.1.2 Brief history of pincer lignads………………………………………………………3
1.1.3 Synthesis of pyrrolyl pyridine pincers………………………………….………….4
1.2 Result & Discussion………………………………………………………………………8
Chapter 2 Ni(II) complexes supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine
ligand……………………………………………………………………………………………..12
2.1 Introduction……………………………………………………………………………..12
2.1.1 Significance of nickel chemistry…………………………………………………12
2.1.2 Applications of nickel(II) pincer complexes……………………………………13
2.2 Nickel(II) acetonitrile complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine.................................................................................................................16
2.3 Nickel(II) carbonyl complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine…………………………………………………………………………….……19
2.3.1 Introduction………………………………………………………………….……19
2.3.2 Result & discussion………………………………………………………..…….21
2.4 Nickel(II) ammonia complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine……………………………………………………………………………….…24
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2.4.1 Introduction……………………………………………………………………....24
2.4.2 Result & discussion………………………………………..……………………25
Chapter 3 Conclusion…………………………………………………………………….……..28
Chapter 4 Experimental Details………………………………………………………..………30
4.1 Synthesis of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine…………………………….30
4.2 Synthesis of LNiCH3CN…………………………………………………...……..31
4.3 Synthesis of LNiCO………………………………………………………………32
4.4 Synthesis of LNiNH3 ………………………………………………………..……33
Appendix A X-ray Data Collection and Selected Bond Distance………………..…………35
Appendix B Selected Spectroscopy Data…………………………………………….………82
References……………………………………………………………………………………….90
Biographical Information………………………………………………………………………..95
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List of Illustrations
Figure 1. General structure of the pincer-type complexes……………………………………2
Figure 2. Complexes with pincer ligands, synthesized by Shaw and coworkers…….…….3
Figure 3. Van Koten synthesis of Pd- and Pt-complexes with (NCN) pincer ligand..….….3
Figure 4. Development of pincer ligands………………………………………………….……4
Figure 5. One step synthesis of 3,5-disubstitued-2-pyridylpyrroles………………….…..….5
Figure 6. Synthesis of 2,6-bis(3,5-diphenylpyrrol-2-yl)pyridine…………………….….…….6
Figure 7. Synthesis of 2,6-bis(3,5-di-methylpyrrol-2-yl)pyridine………………….…………7
Figure 8. Synthesis of 2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine……………….….………7
Figure 9. Synthesis of 2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine……………………….….…….9
Figure 10. ORTEP diagram of the molecular structure of ligand……………..…….……...11
Figure 11. Nickel pincer complexes prepared by Liang and coworkers…………...….…..14
Figure 12. Nickel pincer complexes prepared by Vivic and coworkers…………….…..….14
Figure 13. Nickel pincer complexes prepared by Inamoto and coworkers………..….…..15
Figure 14. Cross coupling reaction catalyzed by nickel pincer complex……………….…15
Figure 15. Nickel pincer complex used for CO2 reduction prepared by Guan and
coworkers…………………………………………………………………………….……….….16
Figure 16. Synthesis of LNiCH3CN……..………………………………………………….….17
Figure 17. ORTEP diagram of the molecular structure of complex……………………..…18
Figure 18. Orbital overlap in carbon monoxide molecule……………………..……..….….20
Figure 19. Orbital overlap in metal carbonyl bond……………………..………..……….….21
Figure 20. Synthesis of LNiCO…………………...……………………………………..……..22
Figure 21. ORTEP diagram of the molecular structure of complex…………………..……23
Figure 22. Synthesis of LNiNH3 …………………………………………...……………….….26
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Figure 23. ORTEP diagram of the molecular structure of complex……………...………..27
1
Figure 24. H NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)…….....……83
Figure 25.
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C NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)………..…..84
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Figure 26. H NMR spectrum of LNi(CH3CN)………………………………....…………….85
Figure 27.
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C NMR spectrum of LNi(CH3CN)……………………………..…..……………86
Figure 28. Infrared spectrum of LNiCO…………………………………………..…..………87
Figure 29. Infrared spectrum of LNiNH3………..………………………………………….…88
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List of Tables
Table 1. Summary of NMR data of LH2, LNiCH3CN, LNiCO, LNiNH3……………………..89
ix
Chapter 1
NNN PINCER LIGAND
1.1 Introduction
1.1.1 Importance of pincer ligands
The term “catalyst” was first mentioned by Jöns Jacob Berzelius in
th
the early 19 century when Sir Humphry Davy observed the hastening of the combustion
of certain gases in the presence of platinum. Since then, the ability to accelerate
chemical transformations under milder conditions with enhanced selectivity has been
very important in chemistry.
1-3, 70
Some milestones of the evolution of catalysis include the
oxidation of hydrochloric acid to chlorine in the presence of cupric salts impregnated in
clay bricks, Ziegler-Natta process for ethylene polymerization, Haber-Bosch process for
the production of ammonia, palladium catalyzed cross-coupling reactions and the olefin
metathesis reactions. The metal-catalyzed cross-coupling reactions and C-H activation
have become significant tools for organic synthesis.
4-9
Intensive research towards the
development of new efficient and selective catalysts grew constantly. The ligand of the
metal complex catalyst is responsible for the stability and reactivity of the designed
catalytic system. The design and amplification of ligands is one of the most crucial part in
catalysis development.
10-16
Pincer-type ligands are one of the most extensively used
ligands for complexation with transition metals in organometallic chemistry.
Pincer ligand systems have a nice feature of tuning the properties of
transition metal complexes to enhance the efficiency of the catalytic processes. Pincer
ligands have names according to the way, they attach to the metals. Pincer ligands are
basically tridentate ligands coordinated to the metal centers with trans-positioned donor
groups D (Figure 1). Conventional pincer ligands have an aromatic framework. Donor
1
groups of the ligand can be changed to provide useful steric and electronic properties.
21
17-
Y groups can be modified to impact the electronic properties of the ligand. The length
of the linkers has an influence on the coordination pocket and spatial arrangement of the
pincer ligand. Furthermore, these positions can also be used to control other properties to
the metal environment, such as chirality or enhanced rigidity. Remote electronic
modifications can be achieved by changing the R group, attached to the backbone of the
ligand. Additionally, labile ligands and non-coordinating counter anions increase the
efficiency of the metal centers. A general structure of the pincer-type complexes has
been illustrated in Figure 1.
Figure 1. General structure of the pincer-type complexes
Properties of pincer complexes relate to the atoms bonded to the
metal center, and in some cases incorporating Y groups as well. For example, the
abbreviated name for the general structure in Figure 1 would be DXD or DYXYD. Pincer
ligands will be explained with this way in this project.
1-3, 70
The tridentate and planar nature of pincer ligands help to form stable
metal complexes. The stability of the complexes provides advantage in catalysis. They
can be heated, exposed to aggressive reagents such as acids, bases and oxidants
without decomposition. High turnover numbers are common with pincer catalysts.
Another important feature of pincer ligands is that ligand properties can be tuned with the
change in substituent in the ligand backbone.
22-27
2
Investigation of the details of reaction
mechanism and the detection and isolation of catalytic intermediates are executed
efficiently with pincer complexes as well.
1.1.2 Brief history of pincer ligands
The first transition metal pincer complex was published by the group of
Shaw in 1970s. The synthesis and characterization of complexes of Ni-, Pd-, Pt- and
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other metals supported by (PCP) pincer ligand were reported (Figure 2) .
Figure 2. Complexes with pincer ligands, synthesized by Shaw and coworkers.
Later the synthesis of another (NCN) pincer ligand and its palladium
and platinum complexes were reported by van Koten and coworkers. The ligand was
lithiated and then it was used as the starting material for the synthesis of Pd- and Ptcomplexes (Figure 3). They also provided X-ray analysis to support the structures.
4
Figure 3. Van Koten synthesis of Pd- and Pt-complexes with (NCN) pincer ligand.
After those seminal studies, pincer ligands received a great deal of
attention of the organometallic chemists for their different applications, such as, specific
3
bond activation, small molecule activation and group transfer. After Shaw’s pincer, Fryzuk
developed a new backbone by changing the PCP platform to PNP platform which
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combined soft phosphines with a hard π-base such as amido group (Figure 4) .
Replacing the carbon by a nitrogen created a more flexible system which has a facial
arrangement unlike the meridional geometry of the carbon analogue.
Liang and Kaska incorporated a new ligand in the library where the
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amido and phosphine residues are connected with a bridge . Then, Ozerov and coworkers improved the ligand by adding alkyl substituents instead of aryl substituents on
the phosphine
1-3, 70
.
Figure 4. Development of pincer ligands
1.1.3 Synthesis of pyrrolyl pyridine pincers
Pyrrolyl pyridine pincers were unknown in the last century. 2,6bis(R)pyridine pincer complexes (R = indolyl, azaindolyl) of some divalent transition
metals have been published by some groups and are known for their optical properties,
and all have conventional k3 pincer connectivity. In fact, the first efficient syntheses of
4
26
one sided pyrrolyl pyridines were reported by McNeill and coworker in 2002 (Figure 5) .
They synthesized 3,5-Disubstituted- and 3,4,5-trisubstituted-2-(2-pyridyl)pyrroles
efficiently from the condensation of 2-(aminomethyl)-pyridine and 1,3-diones. A (2pyridyl)methylamine was identified as the intermediate in the cyclization reaction. Both of
the aliphatic and aromatic substitutions on the pyrrole ring were obtained while
synthesizing the one sided pyrrolyl pyridines.
Figure 5. One step synthesis of 3,5-disubstitued-2-pyridylpyrroles
In the same year 2002, Nagata and Tanaka, reported the synthesis of
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a diphenyl version of pyrrolyl pyridine . They used 2,6-dicarboxaldehyde, a chalcone
(1,3-diphenyl-2-propen-1-one), a thiazolium salt (3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride) a base (sodium tert-butoxide) and ammonium acetate as starting
materials (Figure 6).
5
Figure 6. Synthesis of 2,6-bis(3,5-diphenylpyrrol-2-yl)pyridine
Later in 2007, Dara Bridget Williams reported in PhD dissertation at
The University of Washington, the synthesis of dimethyl substituted pyrrolyl pyridine (2,6bis(3’,5’-dimethyl-2-pyrrolyl)pyridine) (Figure 7).
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This version of the ligand was
synthesized following the condensation process reported by McNeill and Coworker. Here,
acetylacetone was used as chalcone.
6
Figure 7. Synthesis of 2,6-bis(3,5-di-methylpyrrol-2-yl)pyridine
While we were working on our project, another version of this type of
ligand was reported by Caulton and coworker (Figure 8). They synthesized di tert-butyl
substituted pyrrolyl pyridine (2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine) using ditert-butyl
acetyl acetone as chalcone.
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Figure 8. Synthesis of 2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine
Based on the above mentioned discoveries and application of
nickel(II) pincer complexes in various chemical processes it was realized that this could
be a potential area to explore. So, the first plan was to synthesize a new set of ligand,
pyrrolyl pyridine [2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine] that could be used to prepare
7
some nickel(II) pincer complexes, with a modified procedure originally published by
Nagata and Kanaka. Details of the synthesis have been depicted in the next section of
the dissertation.
1.2 Result & discussion
The starting material of the ligand synthesis, 2,6-dicarboxaldehye was
prepared from 2,6-dimethanol pyridine through oxidation with SeO2/Dioxane (Figure 9).
Then, tolualdehyde was stirred at room temperature for 5 h with 4-methylacetophenone
and NaOH in EtOH/H2O to form 1,3-bis(4-tolyl)-2-propen-1-one. Then it was reacted with
2,6-pyridinedicarbaldehyde, 3-benzyl-5-(-hydroxyethyl)-4-methylthiazolium chloride and
sodium t-butoxide in ethanol at reflux for 24 h to form 2,6-bis(2,4-ditolyl-1,4dioxobutyl)pyridine. Finally, the intermediate ketone was reacted with NH 4OAc in ethanol
at reflux for 24 h to form 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2). The intermediate
ketone could also be synthesized using potassium tert-butoxide in ethanol or
triethylamine in dioxane. The intermediate ketone was purified using a silica gel column
before proceeding (Rf = 0.2 with hexane/EtOAc = 9/1). Another interesting point is that
the intermediate product (2,6-bis(2,4-diphenyl-1,4-dioxobutyl)pyridine) is a 1:1 mixture of
two diastereomers. Both diastereomers were collected and used in the next step.
8
Figure 9. Synthesis of 2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine(LH2)
The ligand (LH2) is soluble in polar solvents like acetone and methanol
etc. as well as in non-polar solvents like benzene, pentane, etc. The ligand was
1
characterized by NMR specroscopy, H NMR spectrum of ligand in CDCl3 measured at
room temperature exhibits a sharp singlet at  2.38 ppm which is corresponding to the
9
four methyl groups on the pyrollyl-phenyl rings. A multiplet observed at  6.57 ppm is
assigned to the two pyrollyl ring protons. The aromatic protons are distributed in the
range  7.17 – 7.47 ppm and the two NH protons show a broad resonance at  9.56 ppm.
The ratio between the methyl groups of the pyrollyl-phenyl rings, pyrollyl ring protons, and
the NH protons follow a 6:1:1 pattern supporting the projected structure for the ligand.
13
The C NMR resonances are also coherent with our assignments. Additional evidence
about the composition of the ligand was provided by the HRMS studies, a molecular ion
peak observed at m/z 571.14 is assigned to the ligand.
The molecular structure of the ligand was further confirmed with the
help of X-ray analysis. X-ray quality crystals of the ligand were obtained from a
concentrated ether solution of ligand and its solid state molecular structure is presented
in Figure 10 (The crystal data and refinement details are provided at the chapter 5.1
(Appendix). The X-ray structure reveals that NCCNCCN coordination cavity is nearly
o
planar (torsion angles N1-C4-C19-N2 = -3.16 and N2-C23-C24-N3 = -12.11 ) with the
three donating N atoms (N1, N2 and N3) in a same plane. Interestingly both the pyrroles
t
are directed exclusively inward, which is in contrast with the Bu substituted, similar
molecule reported earlier. The hydrogen bonding between the pyrrole NH groups and the
…
…
pyridine ring nitrogen (N1H N2 = 2.325 and N3H N2 = 2.235 Å) is possibly the reason
for an inward rotation of the two pyrrole rings. The two aryl rings of the pyrrole moieties
o
that are adjacent to the pyridine ring are twisted about 80 from the NCCNCCN plane to
reduce the steric interactions. However the aryl rings that are away from the pyridine ring
are in the same plane.
10
Figure 10. ORTEP diagram of the molecular structure of ligand (LH2)
o
Representative bond lengths (Å) and angles ( ). N1-C1 = 1.372(3), N1-C4 =
1.379(3), N2-C19 = 1.341(3), N2-C23 = 1.353(3), N3-C27 = 1.360(3), N3-C24 = 1.380(3),
C4-C19 = 1.470 (3), C23-C24 = 1.458 (3), C1-C5 = 1.472(3) Å; C1-N1-C4 = 110.9 (2),
N1-C4-C19 = 116.6 (2), C19-N2-C23 = 119.41(19), N3-C24-C23 = 117.7(2), N1-C4-C19o
N2 = -3.16, N2-C23-C24-N3 = -12.11 .
11
Chapter 2
Nickel(II) complexes supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine ligand
2.1 Introduction
2.1.1 Significance of nickel chemistry
Our ancestors used nickel long time before its discovery and isolation.
In 3500 BC Syrian people used to have a bronze which had a small amount of nickel.
th
Coins were made in China from nickel in 235 BC. Finally, in the 17 century, German
miners found a red coloured ore while searching for copper. After analysis, they came to
a conclusion that there was a different material actually present instead of copper. They
named it "Kupfernickel" or Old Nick's Copper, which meant false or bad copper. Swedish
scientist Baron Axel Frederich Cronsted isolated nickel from an ore in 1751.
28-37
Nickel has a long history in the organometallic chemistry. The first
organometallic compound of nickel, nickel carbonyl, Ni(CO) 4 was synthesized in 1890.
Nickel has different coordination numbers 2, 3 and 4. Among the three the coordination
number 2 is most dominant. Many steric constitution of the ligands is possible in this
range e.g. octahedral, trigonal-bipyramidal and tetrahedral etc.
38-41
Nickel is the smallest group 10 metal in the periodic table. It can
execute many of the same rudimentary reactions as palladium or platinum. Because of
these reasons, nickel is often considered a low-cost replacement catalyst for different
cross-coupling reactions. However, there are numerous and diverse nickel catalyzed
reactions reported in the literature. Specially, homogeneous nickel catalysis is currently
drawing significant attention of the scientists. Here, we will discuss recent developments
in homogeneous nickel catalysis as Ni(II) pincers are mostly used as homogenous
catalysts.
12
Oxidative addition i.e. loss of electron density occurs easily around
nickel. On the other hand, reductive elimination is less likely. Palladium catalysis is less
favorable for the oxidative addition that allows the use of cross-coupling electrophiles.
Nickel complexes catalyze the reactions of alkenes and alkynes e.g. oligomerization or
reductive coupling. While in case of β-Hydride elimination, quite opposite trend can be
noticed. Palladium is more efficient in β-Hydride elimination than nickel. Nickel has higher
energy barrier than palladium to Ni–C bond rotation prior to β-hydride elimination.
1-5
Nickel is smaller in atomic radius, and usually has shorter Ni–ligand
bond lengths. Nickel is roughly 2,000 times cheaper than palladium and 10,000 times
cheaper than platinum on a mole-for-mole basis.
1-8
2.1.2 Applications of Nickel(II) pincer complexes
Applications of nickel chemistry comprise of materials science,
polymer synthesis and biocatalysis, homogeneous and heterogeneous catalysis.
However, only application of nickel in homogeneous catalysis will be discussed here as
that relates to Ni(II) pincer complexes. Following are some main areas of homogeneous
catalysis where Ni(II) pincer complexes are prevalent.
Cross-coupling
In organic synthesis cross-coupling reactions of organic halides with
organometallic reagents catalyzed by transition metals have extensive applications e.g.
Kumada, Negishi, Suzuki, and Stille reactions. Both nickel and palladium have been
widely used in cross-coupling reactions as efficient catalysts. Saturated as well as
unsaturated substrates are known for the same purpose.
13
42-50
In 2006, Liang and co-workers published preparation and catalytic
applications of amido-pincer–nickel complexes (Figure 11) for the Kumada coupling of
phenyl iodide or bromide with Grignard reagents.
48-50
Figure 11. Nickel pincer complexes prepared by Liang and coworkers
Several Ni–terpy complexes that can catalyze the coupling of alkyl
iodides with alkylzinc reagents efficiently were reported by Vivic and coworkers (Figure
1-5
12).
Figure 12. Nickel pincer complexes prepared by Vivic and coworkers
14
In 2006 Inamoto and co-workers discovered the cross-coupling of aryl
bromides and chlorides with phenylboronic acid by NHCbased CNC-pincer–nickel
1-6
complex (Figure 13).
Figure 13. Nickel pincer complexes prepared by Inamoto and coworkers
Heck reaction
In 2006, Sakamoto and Watanabe reported an air- and moisturestable nickel(II) bis-carbene pincer complex (Figure 14) which executes Heck reaction
and the Suzuki coupling reaction of a variety of aryl halides with good yields of
products.
50
Figure 14. Cross coupling reaction catalyzed by nickel pincer comple
15
Catalytic reduction of CO2
In 2010 Guan and coworker reported a new nickel bis(phosphinite)
pincer complex [2,6-(R2PO)2C6H3]NiCl (LRNiCl, R = cyclopentyl) in one pot from
resorcinol, ClP(C5H9)2, NiCl2, and 4-dimethylaminopyridine which produces a nickel
hydride complex with treatment of LiAlH4 (Figure 15). The nickel hydride complex is able
to reduce CO2 rapidly at room temperature to form a nickel formate complex.
54
Figure 15. Nickel pincer complex used for CO2 reduction prepared by Guan and
coworkers
Considering the significant catalytic efficiency and vast applications of
Ni(II) pincer complexes discussed above, the preliminary goal was to synthesize some
Ni(II) pincer complexes supported by the above mentioned dianionic pincer ligand, 2,6bis(3,5-ditolyl-2-pyrrolyl)pyridine.
2.2 Nickel(II) acetonitrile complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine
Synthesis of one LNi(II)CH3CN complex was first attempted as it could
be used as starting material for preparation of other complexes (Figure 16). The ligand
2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was deprotonated by refluxing it with 1.5
equivalent of KH for 1.5 hrs in dry THF under nitrogen atmosphere. Then the excess KH
was removed by filtration under nitrogen. The deprotonated potassium salt of the ligand
16
was never isolated. The potassium salt of the ligand in dry THF was stirred with one
equivalent of Ni(OTf)2 overnight. Finally THF was removed and the remaining substance
was stirred in acetonitrile for an hour. The NMR spectrum of the substance after removal
of solvent wasn’t clean. Besides desired product peaks, some peaks of unreacted ligand
and some other unknown peaks were observed. The LNi(II)CH3CN complex was isolated
in pure form after crystallization from slow diffusion of hexane vapor through a solution of
the complex in acetonitrile. The red crystals diffracted well under X-ray. The structure
was confirmed by XRD, NMR and HRMS. But, the (CN) triple bond of the complex didn’t
show any significant absorption under Infrared.
Figure 16. Synthesis of LNiCH3CN
1
The H NMR data is in consistent with expected molecular structure of
the complex LNiCH3CN.The chemical shift values and intensities of the peaks
corresponding to the acetonitrile group, methyl groups of the pyrollyl-phenyl rings and
pyrollyl ring protons are in line with the projected structure of the complex. The
corresponding
13
C NMR signals also correlate with predicted structure of the complex. In
the HRMS studies, a molecular ion peak was observed at m/z 666.21, which is in
consistent with the molecular formula C43H36N4Ni is assigned to the complex.
17
Figure 17. ORTEP diagram of the molecular structure of complex (LNiCH3CN)
o
Representative bond lengths (Å) and angles ( ).
N1-Ni = 1.896 (2) , N2-Ni = 1.844 (2) , N3-Ni = 1.906 (2), N4-Ni = 1.862 (3), N1C4 = 1.398 (4) , N2-C19 = 1.363 (4) , N2-C23 = 1.368 (4) , N3-C24 = 1.387 (4) , C4-C19
= 1.448 (4), C23-C24 = 1.445 (4), N4-C42 = 1.138 (4), C42-C43 = 1.449 (4) Å; N1-Ni-N3
= 166.68 (10), N4-Ni-N3 = 96.58 (10), N1-Ni-N4 = 96.73 (10), N2-C23-C24-N3 = 1.53,
N1-C4-C19-N2 = 1.43
Further, the molecular structure of the complex was determined by
single-crystal X-ray studies (Figure 17). The molecule exhibits a distorted square planar
geometry around the nickel center. All the three donating nitrogens of the pincer ligand
stay in the same plane and the acetonitrile molecule, which is arranged trans to the
o
pyridyl nitrogen, lay slightly out of the plane making an angle of about 9 .
Similar to the ligand, the two pyrrole substituted aryl rings that are
o
adjacent to the pyridine ring are twisted about 68 from the NCCNCCN plane in order to
reduce the steric interactions. The two aryl rings of the rarer side have also rotated about
18
o
60 from the plane of the metal center due to the steric constraints of the coordinated
acetonitrile ligand. The inter pyrrolide angle N1−Ni−N3 is found to be 166.67° and the
dihedral angles NCCN involving pyrrolide and pyridyl rings are found to be 1.53°
(N1C4C19N2) and 1.43° (N2C23C24N3). This indicates that upon chelation the pyrrole
rings are conventionally eclipsed and remain coplanar.
The N-Ni bond length of acetonitrile group (Ni-N4 = 1.862(3) Å) is
found to be shorter than that of the pyrrole ring (Ni-N1 = 1.896(2) and Ni-N3 = 1.906(2)
Å), however the N-Ni bond of the pyridyl nitrogen (Ni-N2 = 1.844(2) Å) is found to be the
shortest among the three. Interestingly, the N-Ni bond distance of acetonitrile group
observed in the current complex, is found to be significantly shorter as compared with the
other nickel-acetonitrile complexes reported earlier (range 2.057 – 2.097 Å).28-36
2.3 Nickel(II) carbonyl complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine
2.3.1 Introduction
Carbon monoxide is one of the most important and widely used small
molecules in organometallic chemistry. Many industrial processes such as catalytic olefin
hydroformylation, olefin/CO copolymerization, Monsanto acetic acid process, water-gas
shift reactions, and thioester formation in Acetyl coenzyme A synthase etc. have
extensive use of numerous carbonylation reactions catalyzed by transition metal
catalysts.
55-61
Instead of rare and expensive transition metals such as Rh, Ru and Ir, the
use of earth-abundant transition metals have attracted huge attention recently because of
their economic advantages. For group 10 elements, scientists are trying to use nickel
instead of Pd and Pt for catalytic carbonylation due to lower cost and toxicity. CO
insertion chemistry has extensive usage in various multiple-component reactions to form
19
carbonyl containing molecules e.g. acid anhydrides, amides, thiocarbamates, lactones
and ketones etc.
55-61
The structure of CO can be explained by the MO description. The lone
pairs of carbon and oxygen are diagonal C(2S)-C(2Pz) hybrid. Also, the lone pairs of
oxygen are weakly directed than the lone pair of carbon. The low energy antibonding
orbitals are able to accept electron density form filled non-bonding metal d orbitals. The
condition for the overlapping of the electron density is that the d orbitals have to be of the
correct symmetry (Figure 18).
44-47
Figure 18. Orbital overlap in carbon monoxide molecule
71
Orbital overlap results increase in the metal-ligand bond strength and
decrease in C-O bond order. This decrease in C-O bond order can be explained by the
lowering of IR absorption frequency. One point to note here that only change in π-bond
strength and not σ-bond strength corresponds to the vibration observed in the Infrared
region.
56-60
Both σ and π bonding are thought to have roles in the bonding
between CO and metal. The π-back bonding occurs from the π-d electron delocalization
from central metal ion to anti-bonding CO orbital and a strong σ-bond forms by the
overlap of σ symmetry orbitals of the metal and CO (Figure 19). This kind of bonding is
20
specially favorable with low valent metals where delocalization of electron density is high
into the ligand orbital. Due to the high delocalization of electrons, carbonyl complexes are
highly covalent in nature.
σ bond
π bond
Figure 19. Orbital overlap in metal carbonyl bond
72
The first nickel carbonyl, nickel tetracarbonyl was discovered by Mond
in 1891.
61
Rapid corrosion of nickel valve was noticed by the workers in the Solvay
process for the production of sodium bicarbonate in which ammonia and carbon dioxide
vapors were used. This observation directed to the detection of trace amounts of carbon
monoxide in the carbon dioxide as well as discovery of nickel tetracarbonyl.
2.3.2 Results & Discussion
Considering the history and importance of nickel carbonyl complexes
and nice accommodation of acetonitrile in the ligand pocket, synthesis of nickel carbonyl
supported by the same ligand was attempted (Figure 20). The ligand 2,6-bis(3,5-ditolyl2-pyrrolyl)pyridine (LH2) was deprotonated by refluxing the ligand with 1.5 equivalent of
KH for 1.5 hrs in dry THF under nitrogen atmosphere. Then the excess KH was removed
21
by filtration under nitrogen. The deprotonated potassium salt of the ligand was taken to
the next step without isolation. The potassium salt of the ligand in dry THF was stirred
with one equivalent of Ni(OTf)2 overnight. Finally THF was removed and the remaining
substance was stirred in ether for few minutes. Then the solution was left to settle down.
There was a precipitation of insoluble substances. The clear solution was slowly collected
with a syringe and passed through a celite bed to completely separate the insoluble part.
o
Then carbon monoxide gas was passed through the ether solution for 20 minutes at 0 C
temperature. The solution saturated with carbon monoxide was left stirring for another 40
minutes. Finally, after filtration through celite bed the volume of the solution was
o
decreased to one third of its initial volume and kept in the -30 C freezer for few days for
crystallization. The bright red crystals diffracted well under X-ray and indicated one CO
molecule is attached to the nickel center. The IR spectrum shows a sharp absorption of
-1
CO at 2101 cm . The absorption frequency is in the classical region as it is less than the
-1
free carbon monoxide (2143 cm ) but well above observed range of other nickel(II)
-1
1
13
carbonyl complexes (2030-2070 cm ). The H NMR and C NMR also supported the
desired product formation. Interestingly, there was a peak for CO carbon at 174.4 in
NMR which sometimes doesn’t show up in metal carbonyls.
Figure 20. Synthesis of LNiCO
22
13
C
Further, the molecular structure of the complex was determined by
single-crystal X-ray studies (Figure 21). The molecule exhibits a distorted square planar
geometry around the nickel center. All the three donating nitrogens of the pincer ligand
stay in the same plane and the carbon monoxide molecule, which is arranged trans to the
o
pyridyl nitrogen, lay slightly out of the plane making an angle of about 27 .
Figure 21. ORTEP diagram of the molecular structure of complex
o
Representative bond lengths (Å) and angles ( ).
Ni-C22 = 1.808 (3) , Ni-N1 = 1.853 (3) , Ni-N2 = 1.8682 (19) , Ni-N2 = 1.8683
(19), N1-C3 = 1.364 (3) , N2-C7 = 1.372 (3) , N2-C4 = 1.393 (3) , C1-C2 = 1.386 (3) , C4C5 = 1.401 (3), C6-C7 = 1.390 (3), C8-C13 = 1.400 (3), C9-C10 = 1.389 (3) Å; N1-Ni-N2
= 83.19 (6), N1-Ni-C22 = 160.43 (14), Ni-N1-C3 = 117.69 (14), N1-C3-C4-N2 = 2.59
23
Similar to the ligand, the two pyrrole substituted aryl rings that are
o
adjacent to the pyridine ring are twisted about 44 from the NCCNCCN plane in order to
reduce the steric interactions. The two aryl rings of the rear side have also rotated about
o
50 from the plane of the metal center due to the steric constraints of the coordinated
acetonitrile ligand. The inter pyrrolide angle N1−Ni−N2 is found to be 83.19 °. The
molecule is symmetrical. Both the dihedral angles NCCN involving pyrrolide and pyridyl
rings are found to be 2.59 ° for (N1C3C4N2). This indicates that upon chelation the
pyrrole rings are conventionally eclipsed and remain coplanar.
The C22-Ni bond length of CO group (Ni-C22 = 1.808 (3) Å) is found to
be shorter than that of the pyrrole ring (Ni-N2 = 1.8682 (19) and Ni-N2 = 1.8683 (19) Å),
however the N-Ni bond of the pyridyl nitrogen (Ni-N2 = 1.853 (3) Å) is found to be shorter
than that of pyrrole ring and longer than that of carbon monoxide group. Interestingly, the
Ni(II)-CO bond distance of 1.808 Å observed in the current complex, is found to be well
in the range of observed for other nickel(II) carbonyl complexes (range 1.73 – 1.83 Å).
2.4 Ni(II) ammonia complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine
2.4.1 Introduction
Activation of small molecules such as N2, H2, O2, CO, NH3 with
transition-metal complexes has huge application in synthetic chemistry. Multidentate
ligands have shown some important uses in small molecule activation by enhancing the
reactivities of the metal center or facilitating ligand-based redox reactions.
62-63
Pincer and
pincer-like ligands featuring relatively different conformational flexible frameworks are
well known for participating in this kind of reactions.
64-66
In this context, after obtaining CO
adduct with Ni(II) supported by the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2),
24
focus was shifted to isolate an ammonia adduct with Ni(II) supported by the same ligand.
The catalytic ammonia decomposition chemistry has been explored by a large group of
scientists recently owing to its many important applications. Ammonia is a potential
energy carrier for fuel cells due to its high hydrogen storage capacity and the possibility
to produce hydrogen without toxic or greenhouse gases as byproducts. Besides, it is a
precursor of aromatic amines that are highly useful and valuable compounds with
numerous uses in the pharmaceutical, agrochemical and polymer industries. Huge
abundance on earth and extremely low cost made ammonia one of the most useful
commodity chemicals. Hartwig and Turculet groups have investigated addition of
ammonia to the Iridium pincer complexes. Parvez and coworker activated ammonia with
a Ni(II) pincer complex. Leitner group reported rhodium pincer complex catalyzed
hydroamination of ethylene with ammonia. Still ammonia activation with pincer
complexes is relatively scarce in literature.
62-67
2.4.2 Result & Discussion
Based on the above facts, synthesis of the ammonia adduct with Ni(II)
supported by the same ligand, 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was attempted
(Figure 22). First, the ligand was deprotonated by refluxing the ligand with 1.5 equivalents
of KH for 1.5 h in dry THF under nitrogen atmosphere. Then, the excess KH was
removed by filtration under nitrogen. The deprotonated potassium salt of the ligand was
taken to the next step without isolation. The potassium salt of the ligand in dry THF was
stirred with one equivalent of Ni(OTf)2 overnight. Finally, THF was removed and the
remaining substance was stirred in ether for few minutes. Then the solution was left to
settle down. There was a precipitation of insoluble substances. The clear solution was
slowly collected with a syringe and passed through a celite bed to completely separate
25
the insoluble part. Then ammonia gas was passed through the ether solution for 20
o
minutes at 0 C temperature. The solution saturated with ammonia was left stirring for
another 40 minutes. Finally, after filtration through celite bed the volume of the solution
o
was decreased to one third of its initial volume and kept in the -30 C freezer for few days
for crystallization. The bright red crystals diffracted well under X-ray and indicated one
ammonia molecule is attached to the nickel center. The IR spectrum shows sharp
-1
1
absorptions of N-H at 3309.6, 3360.2 cm . The H NMR and
13
C NMR also supported the
desired product formation. The three NH3 protons give a singlet at  0.49 .
Figure 22. Synthesis of LNiNH3
Further, the molecular structure of the complex was determined by
single-crystal X-ray studies (Figure 23). The molecule exhibits a distorted square planar
geometry around the nickel center. All the three donating nitrogens of the pincer ligand
stay in the same plane and the ammonia molecule, which is arranged trans to the pyridyl
o
nitrogen, lay slightly out of the plane making an angle about 26 .
26
Figure 23. ORTEP diagram of the molecular structure of complex
o
Representative bond lengths (Å) and angles ( ).
Ni-N1 = 1.885 (10) , Ni-N2 = 1.849 (10) , Ni-N3 = 1.887 (10), Ni-N4 = 1.929 (11),
N1-C4 = 1.387 (4) , N2-C9 = 1.356 (15) , N2-C5 = 1.355 (15) , N3-C13 = 1.365 (15) , C4C5 = 1.440 (17), C23-C24 = 1.391 (2), C38-C39 = 1.388 (2) Å; N1-Ni-N3 = 163.95 (5),
N4-Ni-N3 = 98.60 (5), N1-Ni-N4 = 96.98 (5), N2-C9-C10-N3 = 6.68, N1-C4-C19-N2 =
4.49
Similar to the ligand, the two pyrrole substituted aryl rings that are
o
adjacent to the pyridine ring are twisted about 41 from the NCCNCCN plane in order to
reduce the steric interactions. The two aryl rings of the rarer side have also rotated about
o
43 from the plane of the metal center due to the steric constraints of the coordinated
ammonia ligand. The inter pyrrolide angle N1−Ni−N3 is found to be 163.95 ° and the
dihedral angles NCCN involving pyrrolide and pyridyl rings are found to be 6.68 °
27
(N1C4C19N2) and 4.49 ° (N2C23C24N3). This indicates that upon chelation the pyrrole
rings are conventionally eclipsed and remain coplanar. The N-Ni bond length of ammonia
group (Ni-N4 = 1.929(11) Å) is found to be longer than that of the pyrrole ring (Ni-N1 =
1.885(10) and Ni-N3 = 1.887(10) Å). However the N-Ni bond of the pyridyl nitrogen (NiN2 = 1.849(10) Å) is found to be the shortest among the three.
28
Chapter 3
Conclusion
In conclusion, a new pyridine-pyrrole based NNN pincer ligand was
synthesized and characterized. The ligand synthesis procedure was fast and simple. All
intermediate compounds were prepared with good yields and in pure form. The organic
precursors were purified with vacuum distillation and dried with molecular sieves. The
compound 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was excellent supporting ligand in
the preparation of the different nickel(II) adducts. Two Ni(II) pincer complexes supported
by the same tridentate, dianionic ligand and nitrogen donors, acetonitrile and ammonia
were obtained. Also, it was possible to isolate tetra coordinated nickel(II) carbonyl
complex supported by the same ligand. In all these new compounds the ligand 2,6bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) is bound to the metal in κ3-fashion through the
three nitrogen donor atoms. Single crystals were obtained for all of the compounds and
their structures were confirmed by X-ray analysis. The reactivity of the complexes is yet
to be studied. However, preliminary results were obtained for the synthesis of nickel(II)
hydroxo complex supported by the same ligand and carbon dioxide fixation with the same
nickel(II) hydroxo complex.
29
Chapter 4
Experimental Details
All experiments were done under purified nitrogen atmosphere with
standard schlenk technique or in Glove box. Solvents were bought from various
commercial sources and later purified with an Innovative technology SPS-400 PureSolv
solvent drying system. Some very hygroscopic solvents were distilled over conventional
drying agents and degassed by the freeze-pump-thaw method few times prior to use. All
o
o
glassware were oven dried at 150 C overnight. NMR spectra were recorded at 25 C on
1
JEOL Eclipse 500 and 300 spectrometers ( H: 500.16 MHz or 300.53 MHz;
13
C: 125.77
MHz or 75.57 MHz). Proton and carbon chemical shifts are reported in ppm versus
Me4Si. Infrared (IR) spectra were taken on a JASCO FT-IR 410 spectrometer. The mass
spectra were acquired on Shimadzu IT-TOF-HRMS. Melting points were obtained on a
Mel-Temp II apparatus. All materials were obtained from commercial vendors.
4.1 Synthesis of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine
1,3-bis(4-tolyl)-2-propen-1-one [chalcone] was prepared following
literature known procedure from tolualdehyde and 4-methylacetophenone. Then the
chalcone (1.75 g, 7.4 mmol) was reacted with 2,6-pyridinedicarbaldehyde (0.5 g, 3.7
30
mmol), 3-benzyl-5-(-hydroxyethyl)-4-methylthiazolium chloride (0.2 g, 0.74mmol) and
sodium t-butoxide (0.57 g, 0.74 mmol) in ethanol at reflux for 24 h to form a brown
suspension. Water was added and the mixture was extracted with chloroform. The
chloroform was removed to obtain 2,6-bis(2,4-ditolyl-1,4-dioxobutyl)pyridine. The product
was washed with hexane to achieve an orange solid. Finally, the intermediate ketone was
reacted without further purification with NH4OAc (2.8 g, 37 mmol) in ethanol at reflux for
24 h. Water was added and the yellow solid was filtered and washed with water. Then the
o
crude product was suspended in 10 mL ethanol and refluxed at 100 C for 7 hrs to obtain
1
a yellow solid of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2). (Yield 64%) H NMR (CDCl3,
500.16 MHz, 298 K):  2.38 (s, 12H, CH3) 6.57 (m, 2H), 7.02 (d, J = 8.05, 2H), 7.17-7.22
(m, 9H), 7.38 (d, 4H), 7.47 (d, J = 8 Hz, 4H), 9.56 (2H, NH).
13
1
C{ H} NMR (CDCl3, 125.77
MHz, 298 K):  21.3, 109.7, 117.5, 124.2, 126.6, 127.4, 129.1, 129.8, 133.0, 134.0,
136.3, 136.4, 136.7, 150.3 HRMS-(ESI-) Calculated: 571.29, found: 571.14 M.P. o
o
compound decomposes to form a black substance at 225 C-230 C.
4.2 Synthesis of LNi(CH3CN)
A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1
g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk
flask. THF (ca. 10mL) was added to the mixture at room temperature. The reaction
31
mixture was refluxed for 1.5 hrs. Then it was cooled down to room temperature and
filtered through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate
was added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at
room temperature. Then THF was removed and the residue was filtered in Ether. Ether
was removed under vacuum and 10 mL acetonitrile was added. After 1 h stirring, the
solution was filtered and the volume of the solution was decreased to 4 mL. Finally, the
acetonitrile solution was diffused slowly with hexane to obtain brown crystals at room
temperature. (Yield 34%) H NMR (CDCl3, 500.16 MHz, 298 K):  0.738 (s, 3H, CH3) 2.32
1
(s, 6H, CH3), 2.37 (s, 6H, CH3) 6.06 (s, 2H), 6.60 (d, J = 8 Hz, 2H), 7.04 (t, J = 8 Hz, 1H),
7.15 (m, 8H), 7.36 (d, J = 8 Hz, 4H), 7.62 (d, J = 8.05 Hz, 4H).
13
1
C{ H} NMR (CDCl3,
125.77 MHz, 298 K):  21.2, 110.1, 113.9, 128.0, 129.1, 129.8, 133.9, 134.7, 135.6,
136.0, 136.4, 138.8, 146.2, 154.5 HRMS-(ESI+) Calculated: 666.23, found: 666.21 M.P. o
o
compound decomposes to form a black substance at 175 C-185 C.
4.3 Synthesis of LNi(CO)
A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1
g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk
flask. THF (ca. 10 mL) was added to the mixture at room temperature. The reaction
mixture was refluxed for 1.5 h. Then it was cooled down to room temperature and filtered
32
through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate was
added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at room
temperature. Then THF was removed and the residue was filtered in Ether. Then
anhydrous carbon dioxide gas was passed through the ether solution for 20 minutes at
o
0 C. After 1 hour stirring, the solution was filtered and the volume of the solution was
o
decreased to 4 mL. Red crystals were formed after keeping the solution in the -20 C
freeze for 3 days (Yield 24%) H NMR (CDCl3, 500.16 MHz, 298 K):  2.37 (s, 6H, CH3),
1
2.38 (s, 6H, CH3) 6.21 (s, 2H), 6.77 (d, J = 7.45 Hz, 2H), 7.02 (t, J = 8 Hz, 1H), 7.21 (m,
8H), 7.38 (d, J = 7.5 Hz, 4H), 7.47 (d, J = 8.05 Hz, 4H).
13
1
C{ H} NMR (CDCl3, 125.77
MHz, 298 K):  21.3, 112.1, 117.9, 128.9, 129.3, 129.8, 132.9, 134.0, 136.3, 136.5,
-1
136.8, 147.3, 150.2, 154.4, 174.4 IR (crystals, ATR, selected band) cm : 2100.9 (CO)
HRMS-(ESI+) Calculated: 654.20, found: 654.30 M.P. - compound decomposes to form a
o
o
black substance at 170 C-175 C.
4.4 Synthesis of LNi(NH3)
A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1
g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk
flask. THF (ca. 10 mL) was added to the mixture at room temperature. The reaction
33
mixture was refluxed for 1.5 h. Then it was cooled down to room temperature and filtered
through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate was
added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at room
temperature. Then THF was removed and the residue was filtered in Ether. Then
o
anhydrous ammonia gas was passed through the ether solution for 20 minutes at 0 C.
After 1 hour stirring, the solution was filtered and the volume of the solution was
o
decreased to 4 mL. Red crystals were formed after keeping the solution in the -20 C
freeze for 3 days (Yield 54%) H NMR (CDCl3, 500.16 MHz, 298 K):  0.49 (s, 3H, NH3)
1
2.35 (s, 6H, CH3), 2.38 (s, 6H, CH3) 6.08 (s, 2H), 6.63 (d, J = 8 Hz, 2H), 7.05 (t, J = 8.05
Hz, 1H), 7.19 (m, 8H), 7.36 (d, J = 8.05, 4H), 7.62 (d, J = 7.45 Hz, 4H).
13
1
C{ H} NMR
(CDCl3, 125.77 MHz, 298 K):  21.2, 110.1, 113.9, 128.5, 129.1, 129.7, 133.6, 134.0,
-1
136.0, 136.4, 136.8, 138.5, 144.8, 154.0 IR (crystals, ATR, selected band) cm : 3309.6,
3360.2 (NH) HRMS-(ESI-) Calculated: 644.22, found: 644.19 M.P. - compound
o
o
decomposes to form a black substance at 125 C-130 C.
34
Appendix A
X-ray Data Collection and Selected
Bond Distances & Bond Angles
35
X-ray crystallographic data for 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (File name rad77_a)
Chemical formula moiety
'C41 H35 N3'
Chemical formula weight
569.72
Space group crystal system
monoclinic
Space group IT number
14
Space group name H-M alt
'P 21/c'
Space group name Hall
'-P 2ybc'
Cell length a
14.9028(11)
Cell length b
35.166(3)
Cell length c
5.9568(5)
Cell angle alpha
90
Cell angle beta
100.9910(19)
Cell angle gamma
90
Cell volume
3064.6(4)
Cell formula units Z
4
Cell measurement temperature
100(2)
Cell measurement reflns used
7739
Cell measurement theta min
3.02
Cell measurement theta max
32.16
Exptl crystal description
platy
Exptl crystal colour
yellow
Exptl crystal density diffrn
1.235
Exptl crystal F 000
1208
36
Exptl crystal size max
0.276
Exptl crystal size mid
0.184
Exptl crystal size min
0.118
Diffrn ambient temperature
100(2)
Diffrn radiation wavelength
0.71073
Diffrn radiation type
MoK\a
Diffrn measurement device type
'Bruker D8 Quest'
Diffrn measurement method
'\f and \w scans'
Diffrn reflns number
36061
Diffrn reflns av unetI/netI
0.0709
Diffrn reflns av R equivalents
0.0893
Diffrn reflns limit h min
-19
Diffrn reflns limit h max
19
Diffrn reflns limit k min
-46
Diffrn reflns limit k max
46
Diffrn reflns limit l min
-7
Diffrn reflns limit l max
7
Diffrn reflns theta min
3.016
Diffrn reflns theta max
28.282
Diffrn reflns theta full
25.000
Bond lengths [Å]
N1-C1
1.372(3)
37
N1-C4
1.379(3)
N1-H1
0.86(3)
N2-C19
1.341(3)
N2-C23
1.353(3)
N3-C27
1.360(3)
N3-C24
1.380(3)
N3-H3
0.92(3)
C1-C2
1.375(4)
C1-C5
1.472(3)
C2-C3
1.432(3)
C2-H2
0.9500
C3-C4
1.387(3)
C3-C12
1.478(3)
C4-C19
1.470(3)
C5-C6
1.384(4)
C5-C10
1.401(4)
C6-C7
1.393(4)
C6-H6
0.9500
C7-C8
1.389(4)
C7-H7
0.9500
C8-C9
1.374(4)
C8-C11
1.513(3)
C9-C10
1.393(4)
C9-H9
0.9500
C10-H10
0.9500
38
C11-H11A
0.9800
C11-H11B
0.9800
C11-H11C
0.9800
C12-C13
1.394(3)
C12-C17
1.402(3)
C13-C14
1.388(3)
C13-H13
0.9500
C14-C15
1.393(4)
C14-H14
0.9500
C15-C16
1.392(4)
C15-C18
1.510(4)
C16-C17
1.391(3)
C16-H16
0.9500
C17-H17
0.9500
C18-H18A
0.9800
C18-H18B
0.9800
C18-H18C
0.9800
C19-C20
1.402(3)
C20-C21
1.387(3)
C20-H20
0.9500
C21-C22
1.376(3)
C21-H21
0.9500
C22-C23
1.400(3)
C22-H22
0.9500
C23-C24
1.458(3)
39
C24-C25
1.393(3)
C25-C26
1.417(3)
C25-C28
1.492(3)
C26-C27
1.390(3)
C26-H26
0.9500
C27-C35
1.469(3)
C28-C29
1.386(3)
C28-C33
1.396(3)
C29-C30
1.391(3)
C29-H29
0.9500
C30-C31
1.385(4)
C30-H30
0.9500
C31-C32
1.392(4)
C31-C34
1.509(3)
C32-C33
1.398(3)
C32-H32
0.9500
C33-H33
0.9500
C34-H34A
0.9800
C34-H34B
0.9800
C34-H34C
0.9800
C35-C36
1.394(3)
C35-C40
1.396(3)
C36-C37
1.389(3)
C36-H36
0.9500
C37-C38
1.398(3)
40
C37-H37
0.9500
C38-C39
1.383(4)
C38-C41
1.515(3)
C39-C40
1.394(3)
C39-H39
0.9500
C40-H40
0.9500
C41-H41A
0.9800
C41-H41B
0.9800
C41-H41C
0.9800
Bond angles [deg]
C1-N1-C4
110.9(2)
C1-N1-H1
128.7(19)
C4-N1-H1
119.8(19)
C19-N2-C23
119.41(19)
C27-N3-C24
111.57(19)
C27-N3-H3
133(2)
C24-N3-H3
115(2)
N1-C1-C2
106.9(2)
N1-C1-C5
120.1(2)
C2-C1-C5
132.9(2)
C1-C2-C3
108.3(2)
41
C1-C2-H2
125.8
C3-C2-H2
125.8
C4-C3-C2
106.8(2)
C4-C3-C12
128.9(2)
C2-C3-C12
124.2(2)
N1-C4-C3
107.1(2)
N1-C4-C19
116.6(2)
C3-C4-C19
136.3(2)
C6-C5-C10
117.8(2)
C6-C5-C1
121.4(2)
C10-C5-C1
120.8(2)
C5-C6-C7
121.3(3)
C5-C6-H6
119.3
C7-C6-H6
119.3
C8-C7-C6
121.0(3)
C8-C7-H7
119.5
C6-C7-H7
119.5
C9-C8-C7
117.7(2)
C9-C8-C11
121.3(2)
C7-C8-C11
121.0(3)
C8-C9-C10
122.1(3)
C8-C9-H9
118.9
C10-C9-H9
118.9
C9-C10-C5
120.1(3)
C9-C10-H10
119.9
42
C5-C10-H10
119.9
C8-C11-H11A
109.5
C8-C11-H11B
109.5
H11A-C11-H11B
109.5
C8-C11-H11C
109.5
H11A-C11-H11C
109.5
H11B-C11-H11C
109.5
C13-C12-C17
117.7(2)
C13-C12-C3
121.1(2)
C17-C12-C3
121.2(2)
C14-C13-C12
121.4(2)
C14-C13-H13
119.3
C12-C13-H13
119.3
C13-C14-C15
121.0(2)
C13-C14-H14
119.5
C15-C14-H14
119.5
C16-C15-C14
118.0(2)
C16-C15-C18
120.6(2)
C14-C15-C18
121.4(2)
C17-C16-C15
121.3(2)
C17-C16-H16
119.3
C15-C16-H16
119.3
C16-C17-C12
120.7(2)
C16-C17-H17
119.7
C12-C17-H17
119.7
43
C15-C18-H18A
109.5
C15-C18-H18B
109.5
H18A-C18-H18B
109.5
C15-C18-H18C
109.5
H18A-C18-H18C
109.5
H18B-C18-H18C
109.5
N2-C19-C20
122.2(2)
N2-C19-C4
114.48(19)
C20-C19-C4
123.3(2)
C21-C20-C19
117.7(2)
C21-C20-H20
121.1
C19-C20-H20
121.1
C22-C21-C20
120.6(2)
C22-C21-H21
119.7
C20-C21-H21
119.7
C21-C22-C23
118.6(2)
C21-C22-H22
120.7
C23-C22-H22
120.7
N2-C23-C22
121.4(2)
N2-C23-C24
114.24(18)
C22-C23-C24
124.4(2)
N3-C24-C25
106.2(2)
N3-C24-C23
117.7(2)
C25-C24-C23
136.1(2)
C24-C25-C26
107.59(19)
44
C24-C25-C28
126.2(2)
C26-C25-C28
126.1(2)
C27-C26-C25
107.9(2)
C27-C26-H26
126.0
C25-C26-H26
126.0
N3-C27-C26
106.69(19)
N3-C27-C35
121.4(2)
C26-C27-C35
131.9(2)
C29-C28-C33
118.1(2)
C29-C28-C25
121.9(2)
C33-C28-C25
120.0(2)
C28-C29-C30
121.3(2)
C28-C29-H29
119.4
C30-C29-H29
119.4
C31-C30-C29
121.0(2)
C31-C30-H30
119.5
C29-C30-H30
119.5
C30-C31-C32
118.2(2)
C30-C31-C34
120.5(2)
C32-C31-C34
121.4(2)
C31-C32-C33
121.0(2)
C31-C32-H32
119.5
C33-C32-H32
119.5
C28-C33-C32
120.5(2)
C28-C33-H33
119.8
45
C32-C33-H33
119.8
C31-C34-H34A
109.5
C31-C34-H34B
109.5
H34A-C34-H34B
109.5
C31-C34-H34C
109.5
H34A-C34-H34C
109.5
H34B-C34-H34C
109.5
C36-C35-C40
118.1(2)
C36-C35-C27
121.0(2)
C40-C35-C27
120.9(2)
C37-C36-C35
120.8(2)
C37-C36-H36
119.6
C35-C36-H36
119.6
C36-C37-C38
121.1(2)
C36-C37-H37
119.5
C38-C37-H37
119.5
C39-C38-C37
118.0(2)
C39-C38-C41
121.4(2)
C37-C38-C41
120.6(2)
C38-C39-C40
121.3(2)
C38-C39-H39
119.3
C40-C39-H39
119.3
C39-C40-C35
120.7(2)
C39-C40-H40
119.7
C35-C40-H40
119.7
46
C38-C41-H41A
109.5
C38-C41-H41B
109.5
H41A-C41-H41B
109.5
C38-C41-H41C
109.5
H41A-C41-H41C
109.5
H41B-C41-H41C
109.5
X-ray crystallographic data for LNi(CH3CN) (File name - dias960_0m_a)
Chemical formula moiety
'C49H50N4Ni'
Chemical formula weight
753.64
Space group crystal system
Triclinic
Space group name H-M alt
'P-1'
Cell length a
11.2735(16)
Cell length b
14.1808(19)
Cell length c
14.688(5)
Cell angle alpha
67.162(2)
Cell angle beta
68.881(2)
Cell angle gamma
80.665(2)
Cell volume
2018.0(5)
Cell formula units Z
2
47
Cell measurement temperature
100(2)
Cell measurement reflns used
8799
Cell measurement theta min
2.45
Cell measurement theta max
32.84
Exptl crystal description
prism
Exptl crystal colour
colorless
Exptl crystal density diffrn
1.240
Exptl crystal F 000
800
Exptl crystal size max
0.20
Exptl crystal size mid
0.12
Exptl crystal size min
0.09
Diffrn ambient temperature
100(2)
Diffrn radiation wavelength
0.71073
Diffrn radiation type
MoK\a
Diffrn measurement device type
'Bruker APEX-II CCD'
Diffrn measurement method
'\f and \w scans'
Diffrn reflns number
18916
Diffrn reflns av unetI/netI
0.0746
Diffrn reflns av R equivalents
0.0557
Diffrn reflns limit h min
-14
Diffrn reflns limit h max
14
Diffrn reflns limit k min
-17
Diffrn reflns limit k max
17
Diffrn reflns limit l min
-18
48
Diffrn reflns limit l max
18
Diffrn reflns theta min
2.07
Diffrn reflns theta max
26.37
Bond lengths [Å]
Ni-N2
1.844(2)
Ni-N4
1.862(3)
Ni-N1
1.896(2)
Ni-N3
1.906(2)
N1-C1
1.373(4)
N1-C4
1.398(4)
N2-C19
1.363(4)
N2-C23
1.368(4)
N3-C27
1.379(4)
N3-C24
1.387(4)
N4-C42
1.138(4)
C1-C2
1.402(4)
C1-C5
1.472(4)
C2-C3
1.405(4)
C2-H2
0.9500
C3-C4
1.400(4)
C3-C12
1.488(4)
49
C4-C19
1.448(4)
C5-C10
1.389(4)
C5-C6
1.395(4)
C6-C7
1.384(4)
C6-H6
0.9500
C7-C8
1.395(5)
C7H7
0.9500
C8-C9
1.388(5)
C8-C11
1.510(5)
C9-C10
1.390(4)
C9-H9
0.9500
C10-H10
0.9500
C11-H11A
0.9800
C11-H11B
0.9800
C11-H11C
0.9800
C12-C13
1.394(4)
C12-C17
1.395(4)
C13-C14
1.378(5)
C13-H13
0.9500
C14-C15
1.391(5)
C14-H14
0.9500
C15-C16
1.395(5)
C15-C18
1.508(4)
C16-C17
1.391(4)
C16-H16
0.9500
50
C17-H17
0.9500
C18-H18A
0.9800
C18-H18B
0.9800
C18-H18C
0.9800
C19-C20
1.388(4)
C20-C21
1.379(4)
C20-H20
0.9500
C21-C22
1.387(4)
C21-H21
0.9500
C22-C23
1.387(4)
C22-H22
0.9500
C23-C24
1.445(4)
C24-C25
1.398(4)
C25-C26
1.397(4)
C25-C28
1.482(4)
C26-C27
1.400(4)
C26-H26
0.9500
C27-C35
1.477(4)
C28-C29
1.389(4)
C28-C33
1.389(4)
C29-C30
1.387(4)
C29-H29
0.9500
C30-C31
1.394(5)
C30-H30
0.9500
C31-C32
1.386(5)
51
C31-C34
1.514(4)
C32-C33
1.389(5)
C32-H32
0.9500
C33-H33
0.9500
C34-H34A
0.9800
C34-H34B
0.9800
C34-H34C
0.9800
C35-C40
1.387(5)
C35-C36
1.401(5)
C36-C37
1.383(5)
C36-H36
0.9500
C37-C38
1.382(6)
C37-H37
0.9500
C38-C39
1.394(6)
C38-C41
1.513(5)
C39-C40
1.393(5)
C39-H39
0.9500
C40-H40
0.9500
C41-H41A
0.9800
C41-H41B
0.9800
C41-H41C
0.9800
C42-C43
1.449(4)
C43-H43A
0.9800
C43-H43B
0.9800
C43-H43C
0.9800
52
C44-C45
1.567(9)
C44-H44A
0.9800
C44-H44B
0.9800
C44-H44C
0.9800
C45-C46
1.336(11)
C45-H45A
0.9900
C45-H45B
0.9900
C46-C47
1.517(11)
C46-H46A
0.9900
C46-H46B
0.9900
C47-C48
1.409(9)
C47-H47A
0.9900
C47-H47B
0.9900
C48-C49
1.476(9)
C48-H48A
0.9900
C48-H48B
0.9900
C49-H49A
0.9800
C49-H49B
0.9800
C49-H49C
0.9800
Bond angles [deg]
N2-Ni-N4
167.99(11)
53
N2-Ni-N1
83.38(10)
N4-Ni-N1
96.73(10)
N2-Ni-N3
83.53(10)
N4-Ni-N3
96.58(10)
N1-Ni-N3
166.68(10)
C1-N1-C4
106.5(2)
C1-N1-Ni
138.4(2)
C4-N1-Ni
113.41(18)
C19-N2-C23
122.2(3)
C19-N2-Ni
118.6(2)
C23-N2-Ni
118.0(2)
C27-N3-C24
106.2(2)
C27-N3-Ni
138.7(2)
C24-N3-Ni
112.50(19)
C42-N4-Ni
176.8(3)
N1-C1-C2
109.6(3)
N1-C1-C5
124.9(3)
C2-C1-C5
125.4(3)
C1-C2-C3
107.9(3)
C1-C2-H2
126.1
C3-C2-H2
126.1
C4-C3-C2
105.9(3)
C4-C3-C12
128.3(3)
C2-C3-C12
125.8(3)
N1-C4-C3
110.2(3)
54
N1-C4-C19
113.8(2)
C3-C4-C19
135.0(3)
C10-C5-C6
118.1(3)
C10-C5-C1
119.9(3)
C6-C5-C1
122.0(3)
C7-C6-C5
120.7(3)
C7-C6-H6
119.6
C5-C6-H6
119.6
C6-C7-C8
121.1(3)
C6-C7-H7
119.5
C8-C7-H7
119.5
C9-C8-C7
118.2(3)
C9-C8-C11
120.8(3)
C7-C8-C11
121.1(3)
C8-C9-C10
120.8(3)
C8-C9-H9
119.6
C10-C9-H9
119.6
C5-C10-C9
121.1(3)
C5-C10-H10
119.4
C9-C10-H10
119.4
C8-C11-H11A
109.5
C8-C11-H11B
109.5
H11A-C11-H11B
109.5
C8-C11-H11C
109.5
H11A-C11-H11C
109.5
55
H11B-C11-H11C
109.5
C13-C12-C17
117.9(3)
C13-C12-C3
120.8(3)
C17-C12-C3
121.3(3)
C14-C13-C12
121.1(3)
C14-C13-H13
119.5
C12-C13-H13
119.5
C13-C14-C15
121.6(3)
C13-C14-H14
119.2
C15-C14-H14
119.2
C14-C15-C16
117.4(3)
C14-C15-C18
121.6(3)
C16-C15-C18
120.9(3)
C17-C16-C15
121.2(3)
C17-C16-H16
119.4
C15-C16-H16
119.4
C16-C17-C12
120.7(3)
C16-C17-H17
119.7
C12-C17-H17
119.7
C15-C18-H18A
109.5
C15-C18-H18B
109.5
H18A-C18-H18B
109.5
C15-C18-H18C
109.5
H18A-C18-H18C
109.5
H18B-C18-H18C
109.5
56
N2-C19-C20
119.2(3)
N2-C19-C4
110.4(3)
C20-C19-C4
130.2(3)
C21-C20-C19
119.1(3)
C21-C20-H20
120.5
C19-C20-H20
20.5
C20-C21-C22
121.5(3)
C20-C21-H21
119.3
C22-C21-H21
119.3
C23-C22-C21
118.5(3)
C23-C22-H22
120.7
C21-C22-H22
120.7
N2-C23-C22
119.5(3)
N2-C23-C24
110.3(3)
C22-C23-C24
130.1(3)
N3-C24-C25
110.6(3)
N3-C24-C23
114.7(2)
C25-C24-C23
134.0(3)
C26-C25-C24
105.7(3)
C26-C25-C28
127.0(3)
C24-C25-C28
127.2(3)
C25-C26-C27
108.1(3)
C25-C26-H26
125.9
C27-C26-H26
125.9
N3-C27-C26
109.3(3)
57
N3-C27-C35
124.6(3)
C26-C27-C35
125.6(3)
C29-C28-C33
117.9(3)
C29-C28-C25
121.1(3)
C33-C28-C25
121.0(3)
C30-C29-C28
121.5(3)
C30-C29-H29
119.3
C28-C29-H29
119.3
C29-C30-C31
120.7(3)
C29-C30-H30
119.6
C31-C30-H30
119.6
C32-C31-C30
117.5(3)
C32-C31-C34
122.1(3)
C30-C31-C34
120.4(3)
C31-C32-C33
121.9(3)
C31-C32-H32
119.1
C33-C32-H32
119.1
C28-C33-C32
120.4(3)
C28-C33-H33
119.8
C32-C33-H33
119.8
C31-C34-H34A
109.5
C31-C34-H34B
109.5
H34A-C34-H34B
109.5
C31-C34-H34C
109.5
H34A-C34-H34C
109.5
58
H34B-C34-H34C
109.5
C40-C35-C36
118.4(3)
C40-C35-C27
122.3(3)
C36-C35-C27
119.1(3)
C37-C36-C35
120.8(4)
C37-C36-H36
119.6
C35-C36-H36
119.6
C38-C37-C36
120.9(4)
C38-C37-H37
119.6
C36-C37-H37
119.6
C37-C38-C39
118.7(3)
C37-C38-C41
120.5(4)
C39-C38-C41
120.8(4)
C40-C39-C38
120.6(4)
C40-C39-H39
119.7
C38-C39-H39
119.7
C35-C40-C39
120.5(3)
C35-C40-H40
119.7
C39-C40-H40
119.7
C38-C41-H41A
109.5
C38-C41-H41B
109.5
H41A-C41-H41B
109.5
C38-C41-H41C
109.5
H41A-C41-H41C
109.5
H41B-C41-H41C
109.5
59
N4-C42-C43
177.0(3)
C42-C43-H43A
109.5
C42-C43-H43B
109.5
H43A-C43-H43B
109.5
C42-C43-H43C
109.5
H43A-C43-H43C
109.5
H43B-C43-H43C
109.5
C45-C44-H44A
109.5
C45-C44-H44B
109.5
H44A-C44-H44B
109.5
C45-C44-H44C
109.5
H44A-C44-H44C
109.5
H44B-C44-H44C
109.5
C46-C45-C44
116.6(9)
C46-C45-H45A
108.1
C44-C45-H45A
108.1
C46-C45-H45B
108.1
C44-C45-H45B
108.1
H45A-C45-H45B
107.3
C45-C46-C47
120.8(10)
C45-C46-H46A
107.1
C47-C46-H46A
107.1
C45-C46-H46B
107.1
C47-C46-H46B
107.1
H46A-C46-H46B
106.8
60
C48-C47-C46
116.6(10)
C48-C47-H47A
108.1
C46-C47-H47A
108.1
C48-C47-H47B
108.1
C46-C47-H47B
108.1
H47A-C47-H47B
107.3
C47-C48-C49
111.3(7)
C47-C48-H48A
109.4
C49-C48-H48A
109.4
C47-C48-H48B
109.4
C49-C48-H48B
109.4
H48A-C48-H48B
108.0
C48-C49-H49A
109.5
C48-C49-H49B
109.5
H49A-C49-H49B
109.5
C48-C49-H49C
109.5
H49A-C49-H49C
109.5
H49B-C49-H49C
109.5
61
X-ray crystallographic data for LNiCO (File name - rad76_0m_a)
Chemical formula moiety
'C42 H33 N3NiO'
Chemical formula weight
654.42
Space group crystal system
monoclinic
Space group IT number
14
Space group name H-M alt
'P 21/c'
Space group name Hall
'-P 2ybc'
Cell length a
6.6482(4)
Cell length b
27.1709(18)
Cell length c
9.1322(6)
Cell angle alpha
90
Cell angle beta
101.0700(12)
Cell angle gamma
90
Cell volume
1618.92(18)
Cell formula units Z
2
Cell measurement temperature
100(2)
Cell measurement reflns used
5886
Cell measurement theta min
3.00
Cell measurement theta max
30.47
Exptl crystal description
platy
Exptl crystal colour
yellow
Exptl crystal density diffrn
1.342
62
Exptl crystal F 000
684
Exptl crystal size max
0.363
Exptl crystal size mid
0.265
Exptl crystal size min
0.048
Diffrn ambient temperature
100(2)
Diffrn radiation wavelength
0.71073
Diffrn radiation type
MoK\a
Diffrn measurement device type
'Bruker D8 Quest'
Diffrn measurement method
'\f and \w scans'
Diffrn reflns number
17505
Diffrn reflns av unetI/netI
0.0429
Diffrn reflns av R equivalents
0.0534
Diffrn reflns limit h min
-8
Diffrn reflns limit h max
8
Diffrn reflns limit k min
-35
Diffrn reflns limit k max
35
Diffrn reflns limit l min
-11
Diffrn reflns limit l max
11
Diffrn reflns theta min
2.999
Diffrn reflns theta max
27.485
Diffrn reflns theta full
25.000
Bond lengths [Å]
63
Ni-C22
1.808(3)
Ni-N1
1.853(3)
Ni-N2
1.8682(19)
Ni-N2
1.8683(19)
O1-C22
1.129(4)
N1-C3
1.364(3)
N1-C3
1.364(3)
N2-C7
1.372(3)
N2-C4
1.393(3)
C1-C2
1.386(3)
C1-C2
1.386(3)
C1-H1
0.9500
C2-C3
1.402(3)
C2-H2
0.9500
C3-C4
1.443(3)
C4-C5
1.401(3)
C5-C6
1.411(3)
C5-C8
1.483(3)
C6-C7
1.390(3)
C6-H6
0.9500
C7-C15
1.478(3)
C8-C9
1.395(3)
C8-C13
1.400(3)
C9-C10
1.389(3)
64
C9-H9
0.9500
C10-C11
1.385(4)
C10-H10
0.9500
C11-C12
1.403(4)
C11-C14
1.515(3)
C12-C13
1.391(3)
C12-H12
0.9500
C13-H13
0.9500
C14-H14A
0.9800
C14-H14B
0.9800
C14-H14C
0.9800
C15-C20
1.396(3)
C15-C16
1.401(3)
C16-C17
1.390(3)
C16-H16
0.9500
C17-C18
1.392(4)
C17-H17
0.9500
C18-C19
1.392(4)
C18-C21
1.512(4)
C19-C20
1.391(3)
C19-H19
0.9500
C20-H20
0.9500
C21-H21A
0.9800
C21-H21B
0.9800
C21-H21C
0.9800
65
Bond angles [deg]
C22-Ni-N1
160.43(14)
C22-Ni-N2
97.39(6)
N1-Ni-N2
83.19(6)
C22-Ni-N2
97.39(6)
N1-Ni-N2
83.19(6)
N2-Ni-N2
165.20(12)
C3-N1-C3
124.2(3)
C3-N1-Ni
117.69(14)
C3-N1-Ni
117.69(14)
C7-N2-C4
107.30(19)
C7-N2-Ni
137.40(16)
C4-N2-Ni
114.65(16)
C2-C1-C2
122.1(3)
C2-C1-H1
118.9
C2-C1-H1
118.9
C1-C2-C3
118.6(2)
C1-C2-H2
120.7
C3-C2-H2
120.7
N1-C3-C2
118.2(2)
N1-C3-C4
110.9(2)
C2-C3-C4
130.9(2)
66
N2-C4-C5
109.6(2)
N2-C4-C3
112.8(2)
C5-C4-C3
137.5(2)
C4-C5-C6
105.6(2)
C4-C5-C8
129.0(2)
C6-C5-C8
125.4(2)
C7-C6-C5
108.4(2)
C7-C6-H6
125.8
C5-C6-H6
125.8
N2-C7-C6
109.1(2)
N2-C7-C15
122.4(2)
C6-C7-C15
128.5(2)
C9-C8-C13
117.6(2)
C9-C8-C5
122.2(2)
C13-C8-C5
120.2(2)
C10-C9-C8
121.0(2)
C10-C9-H9
119.5
C8-C9-H9
119.5
C11-C10-C9
121.6(2)
C11-C10-H10
119.2
C9-C10-H10
119.2
C10-C11-C12
117.8(2)
C10-C11-C14
122.4(2)
C12-C11-C14
119.8(2)
C13-C12-C11
120.7(2)
67
C13-C12-H12
119.6
C11-C12-H12
119.6
C12-C13-C8
121.2(2)
C12-C13-H13
119.4
C8-C13-H13
119.4
C11-C14-H14A
109.5
C11-C14-H14B
109.5
H14A-C14-H14B
109.5
C11-C14-H14C
109.5
H14A-C14-H14C
109.5
H14B-C14-H14C
109.5
C20-C15-C16
118.0(2)
C20-C15-C7
121.5(2)
C16-C15-C7
120.5(2)
C17-C16-C15
120.7(2)
C17-C16-H16
119.7
C15-C16-H16
119.7
C16-C17-C18
121.3(2)
C16-C17-H17
119.3
C18-C17-H17
119.3
C17-C18-C19
118.0(2)
C17-C18-C21
121.5(2)
C19-C18-C21
120.5(2)
C20-C19-C18
121.2(2)
C20-C19-H19
119.4
68
C18-C19-H19
119.4
C19-C20-C15
120.9(2)
C19-C20-H20
119.6
C15-C20-H20
119.6
C18-C21-H21A
109.5
C18-C21-H21B
109.5
H21A-C21-H21B
109.5
C18-C21-H21C
109.5
H21A-C21-H21C
109.5
H21B-C21-H21C
109.5
O1-C22-Ni
166.0(3)
X-ray crystallographic data for LNiNH3 (File name - rad71_a)
Chemical formula moiety
'C41 H36 N4Ni'
Chemical formula weight
643.45
Space group crystal system
monoclinic
Space group IT number
14
Space group name H-M alt
'P 21/c'
Space group name Hall
'-P 2ybc'
Cell length a
15.9773(6)
Cell length b
14.9441(5)
69
Cell length c
14.3238(5)
Cell angle alpha
90
Cell angle beta
107.8140(8)
Cell angle gamma
90
Cell volume
3256.1(2)
Cell formula units Z
4
Cell measurement temperature
100(2)
Cell measurement reflns used
9841
Cell measurement theta min
2.99
Cell measurement theta max
39.36
Exptl crystal description
platy
Exptl crystal colour
red
Exptl crystal density diffrn
1.313
Exptl crystal F 000
1352
Exptl crystal size max
0.459
Exptl crystal size mid
0.409
Exptl crystal size min
0.140
Diffrn ambient temperature
100(2)
Diffrn radiation wavelength
0.71073
Diffrn radiation type
MoK\a
Diffrn measurement device type
'Bruker D8 Quest'
Diffrn measurement method
'\f and \w scans'
Diffrn reflns number
48278
Diffrn reflns av unetI/netI
0.0200
Diffrn reflns av R equivalents
0.0260
70
Diffrn reflns limit h min
-22
Diffrn reflns limit h max
22
Diffrn reflns limit k min
-35
Diffrn reflns limit k max
35
Diffrn reflns limit l min
-21
Diffrn reflns limit l max
21
Diffrn reflns theta min
2.876
Diffrn reflns theta max
30.508
Diffrn reflns theta full
25.000
Bond lengths [Å]
Ni-N2
1.8490(10)
Ni-N1
1.8857(10)
Ni-N3
1.8877(10)
Ni-N4
1.9293(11)
N1-C1
1.3679(16)
N1-C4
1.3870(15)
N2-C5
1.3553(15)
N2-C9
1.3557(15)
N3-C13
1.3654(15)
N3-C10
1.3920(15)
N4-H1N4
0.89(3)
N4-H2N4
0.85(3)
71
N4-H3N4
0.86(3)
C1-C2
1.3993(17)
C1-C14
1.4698(17)
C2-C3
1.4085(18)
C2-H2
0.9500
C3-C4
1.3968(17)
C3-C21
1.4816(17)
C4-C5
1.4400(17)
C5-C6
1.3988(16)
C6-C7
1.3891(18)
C6-H6
0.9500
C7-C8
1.3931(17)
C7-H7
0.9500
C8-C9
1.3957(17)
C8-H8
0.9500
C9-C10
1.4512(16)
C10-C11
1.4040(16)
C11-C12
1.4150(17)
C11-C35
1.4732(17)
C12-C13
1.3994(17)
C12-H12
0.9500
C13-C28
1.4702(17)
C14-C19
1.3975(19)
C14-C15
1.4021(19)
C15-C16
1.3906(18)
72
C15-H15
0.9500
C16-C17
1.392(2)
C16-H16
0.9500
C17-C18
1.391(2)
C17-C20
1.509(2)
C18-C19
1.3927(19)
C18-H18
0.9500
C19-H19
0.9500
C20-H20A
0.9800
C20-H20B
0.9800
C20-H20C
0.9800
C21-C22
1.3916(19)
C21-C26
1.3936(19)
C22-C23
1.3938(19)
C22-H22
0.9500
C23-C24
1.391(2)
C23-H23
0.9500
C24-C25
1.3873(19)
C24-C27
1.5027(19)
C25-C26
1.3922(18)
C25-H25
0.9500
C26-H26
0.9500
C27-H27A
0.9800
C27-H27B
0.9800
C27-H27C
0.9800
73
C28-C33
1.3984(18)
C28-C29
1.3980(17)
C29-C30
1.3893(19)
C29-H29
0.9500
C30-C31
1.389(2)
C30-H30
0.9500
C31-C32
1.396(2)
C31-C34
1.5037(19)
C32-C33
1.3917(18)
C32-H32
0.9500
C33-H33
0.9500
C34-H34A
0.9800
C34-H34B
0.9800
C34-H34C
0.9800
C35-C36
1.3976(18)
C35-C40
1.3992(17)
C36-C37
1.3912(18)
C36-H36
0.9500
C37-C38
1.3961(19)
C37-H37
0.9500
C38-C39
1.388(2)
C38-C41
1.508(2)
C39-C40
1.3945(19)
C39-H39
0.9500
C40-H40
0.9500
74
C41-H41A
0.9800
C41-H41B
0.9800
C41-H41C
0.9800
Bond angles [deg]
N2-Ni-N1
83.41(4)
N2-Ni-N3
82.95(4)
N1-Ni-N3
163.95(5)
N2-Ni-N4
162.16(5)
N1-Ni-N4
96.98(5)
N3-Ni-N4
98.60(5)
C1-N1-C4
106.74(10)
C1-N1-Ni
140.11(9)
C4-N1-Ni
113.07(8)
C5-N2-C9
123.28(11)
C5-N2-Ni
117.39(8)
C9-N2-Ni
118.43(8)
C13-N3-C10
107.19(10)
C13-N3-Ni
138.51(9)
C10-N3-Ni
114.30(8)
Ni-N4-H1N4
112.8(16)
75
Ni-N4-H2N4
120.5(18)
H1N4-N4-H2N4
103(2)
Ni-N4-H3N4
106.2(15)
H1N4-N4-H3N4
112(2)
H2N4-N4-H3N4
102(2)
N1-C1-C2
109.45(11)
N1-C1-C14
123.63(11)
C2-C1-C14
126.53(11)
C1-C2-C3
107.83(11)
C1-C2-H2
126.1
C3-C2-H2
126.1
C4-C3-C2
105.53(11)
C4-C3-C21
126.96(11)
C2-C3-C21
127.49(11)
N1-C4-C3
110.44(11)
N1-C4-C5
113.97(10)
C3-C4-C5
135.44(11)
N2-C5-C6
119.42(11)
N2-C5-C4
110.79(10)
C6-C5-C4
129.79(11)
C7-C6-C5
118.22(11)
C7-C6-H6
120.9
C5-C6-H6
120.9
C6-C7-C8
121.36(12)
C6-C7-H7
119.3
76
C8-C7-H7
119.3
C7-C8-C9
118.75(11)
C7-C8-H8
120.6
C9-C8-H8
120.6
N2-C9-C8
118.92(11)
N2-C9-C10
110.49(10)
C8-C9-C10
130.58(11)
N3-C10-C11
109.98(10)
N3-C10-C9
113.08(10)
C11-C10-C9
136.94(11)
C10-C11-C12
105.46(11)
C10-C11-C35
130.14(11)
C12-C11-C35
124.37(11)
C13-C12-C11
107.90(11)
C13-C12-H12
126.1
C11-C12-H12
126.1
N3-C13-C12
109.46(11)
N3-C13-C28
123.82(11)
C12-C13-C28
126.61(11)
C19-C14-C15
117.93(12)
C19-C14-C1
120.81(12)
C15-C14-C1
121.12(12)
C16-C15-C14
120.75(13)
C16-C15-H15
119.6
C14-C15-H15
119.6
77
C15-C16-C17
121.14(14)
C15-C16-H16
119.4
C17-C16-H16
119.4
C18-C17-C16
118.21(13)
C18-C17-C20
121.27(15)
C16-C17-C20
120.48(15)
C17-C18-C19
121.08(13)
C17-C18-H18
119.5
C19-C18-H18
119.5
C18-C19-C14
120.87(13)
C18-C19-H19
119.6
C14-C19-H19
119.6
C17-C20-H20A
109.5
C17-C20-H20B
109.5
H20A-C20-H20B
109.5
C17-C20-H20C
109.5
H20A-C20-H20C
109.5
H20B-C20-H20C
109.5
C22-C21-C26
117.84(12)
C22-C21-C3
120.99(12)
C26-C21-C3
121.17(12)
C21-C22-C23
120.87(13)
C21-C22-H22
119.6
C23-C22-H22
119.6
C24-C23-C22
121.30(13)
78
C24-C23-H23
119.4
C22-C23-H23
119.4
C25-C24-C23
117.63(12)
C25-C24-C27
121.09(13)
C23-C24-C27
121.28(13)
C24-C25-C26
121.38(13)
C24-C25-H25
119.3
C26-C25-H25
119.3
C25-C26-C21
120.92(12)
C25-C26-H26
119.5
C21-C26-H26
119.5
C24-C27-H27A
109.5
C24-C27-H27B
109.5
H27A-C27-H27B
109.5
C24-C27-H27C
109.5
H27A-C27-H27C
109.5
H27B-C27-H27C
109.5
C33-C28-C29
118.32(12)
C33-C28-C13
121.78(11)
C29-C28-C13
119.81(12)
C30-C29-C28
120.61(13)
C30-C29-H29
119.7
C28-C29-H29
119.7
C29-C30-C31
121.15(13)
C29-C30-H30
119.4
79
C31-C30-H30
119.4
C30-C31-C32
118.43(12)
C30-C31-C34
120.21(14)
C32-C31-C34
121.36(15)
C33-C32-C31
120.77(13)
C33-C32-H32
119.6
C31-C32-H32
119.6
C32-C33-C28
120.69(12)
C32-C33-H33
119.7
C28-C33-H33
119.7
C31-C34-H34A
109.5
C31-C34-H34B
109.5
H34A-C34-H34B
109.5
C31-C34-H34C
109.5
H34A-C34-H34C
109.5
H34B-C34-H34C
109.5
C36-C35-C40
117.73(12)
C36-C35-C11
121.83(11)
C40-C35-C11
120.39(12)
C37-C36-C35
121.15(12)
C37-C36-H36
119.4
C35-C36-H36
119.4
C36-C37-C38
121.06(13)
C36-C37-H37
119.5
C38-C37-H37
119.5
80
C39-C38-C37
117.85(13)
C39-C38-C41
121.65(14)
C37-C38-C41
120.50(14)
C38-C39-C40
121.50(13)
C38-C39-H39
119.3
C40-C39-H39
119.3
C39-C40-C35
120.72(13)
C39-C40-H40
119.6
C35-C40-H40
119.6
C38-C41-H41A
109.5
C38-C41-H41B
109.5
H41A-C41-H41B
109.5
C38-C41-H41C
109.5
H41A-C41-H41C
109.5
H41B-C41-H41C
109.5
81
Appendix B
Selected Spectroscopy Data
82
1
Figure 24. H NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)
83
Figure 25.
13
C NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)
84
1
Figure 26. H NMR spectrum of LNi(CH3CN)
85
Figure 27.
13
C NMR spectrum of LNi(CH3CN)
86
Figure 28. Infrared spectrum of LNiCO
87
Figure 29. Infrared spectrum of LNiNH3
88
Table 1. Summary of NMR data of LH2, LNiCH3CN, LNiCO, LNiNH3
1
H
 = 2.38 (s, 12H,
CH3)
6.57 (m, 2H,
pyrrole), 7.02 (d, J =
8.05, 2H), 7.17-7.22
(m, 9H),
7.38 (d, 4H),
7.47 (d, J = 8 Hz,
4H),
9.56 (2H, NH).
1
H
 = 0.738 (s, 3H,
CH3CN)
2.32 (s, 6H, CH3),
2.37 (s, 6H, CH3)
6.06 (s, 2H, pyrrole),
6.60 (d, J = 8 Hz,
2H), 7.04 (t, J = 8
Hz, 1H), 7.15 (m,
8H),
7.36 (d, J = 8 Hz,
4H), 7.62 (d, J =
8.05 Hz, 4H).
1
H
 = 2.37 (s, 6H,
CH3),
2.38 (s, 6H, CH3)
6.21 (s, 2H,pyrrole),
6.77 (d, J = 7.45
Hz, 2H), 7.02 (t, J =
8 Hz, 1H), 7.21 (m,
8H),
7.38 (d, J = 7.5 Hz,
4H), 7.47 (d, J =
8.05 Hz, 4H).
1
13
13
13
13
1
C{ H}
 = 21.3 (CH3),
109.7 (CH pyrrole),
117.5, 124.2, 126.6,
127.4, 129.1, 129.8,
133.0, 134.0, 136.3,
136.4, 136.7,
150.3 (o-C pyridine)
1
C{ H}
 = 21.2 (CH3),
110.1 (CH pyrrole),
113.9, 128.0, 129.1,
129.8, 133.9, 134.7,
135.6, 136.0, 136.4,
138.8, 146.2,
154.5 (o-C pyridine)
1
C{ H}
 = 21.3 (CH3),
112.1 (CH pyrrole),
117.9, 128.9, 129.3,
129.8, 132.9, 134.0,
136.3, 136.5, 136.8,
147.3, 150.2,
154.4(o-C pyridine),
174.4 (CO)
89
H
 = 0.49 (s, 3H,
NH3)
2.35 (s, 6H, CH3),
2.38 (s, 6H, CH3)
6.08 (s, 2H,pyrrole),
6.63 (d, J = 8 Hz,
2H), 7.05 (t, J =
8.05 Hz, 1H), 7.19
(m, 8H),
7.36 (d, J = 8.05,
4H),
7.62 (d, J = 7.45
Hz, 4H).
1
C{ H}
 = 21.2 (CH3),
110.1 (CH pyrrole),
113.9, 128.5, 129.1,
129.7, 133.6, 134.0,
136.0, 136.4, 136.8,
138.5, 144.8,
154.0 (o-C pyridine)
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Biographical Information
Abhijit was born and grew up in West Bengal, India. He received his
B.Sc. and M.Sc. degree in Chemistry from Vidyasagar University, India. There he worked
on organic synthesis and methodologies. He studied synthesis and reactivities of
substituted dihydropyrimidines with a focus on Biginelli reaction under the guidance of Dr.
Sudhir Chandra Pal. Then Abhijit worked as a Junior Research Fellow for 1.5 years at
Department of Organic Chemistry in Indian Association for the Cultivation of Science,
Kolkata, India in the research group of Dr. Saswati Lahiri. There he worked on organic
synthesis and photochemistry. In Fall 2011, Abhijit joined Department of Chemistry and
Biochemistry at UT Arlington. In Spring 2012 he joined Dr. Rasika Dias group and worked
on the project discussed in this thesis. Besides research, he likes to socialize and spend
time in gymnasium.
95