Download complexes with bidentate N,N?-bis(b-phenylcinnamaldehyde)

Polyhedron 21 (2002) 2733 /2742
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Cobalt(II), nickel(II), and zinc(II) complexes with bidentate
N,N?-bis(b-phenylcinnamaldehyde)-1,2-diiminoethane Schiff base:
synthesis and structures
Mehdi Amirnasr a,, Amir H. Mahmoudkhani b, Alireza Gorji a, Saeed Dehghanpour c,
Hamid Reza Bijanzadeh c
a
Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran
b
Department of Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden
c
Department of Chemistry, Tarbiat Modarres University, P.O. Box 14155-4838, Tehran, Iran
Received 7 June 2002; accepted 9 October 2002
Abstract
A series of complexes of the type M(Phca2en)X2, where Phca2en/N ,N ?-bis(b-phenyl-cinnamaldehyde)-1,2-diiminoethane,
M(II) /Co, Ni or Zn and X /Cl, Br, I or NCS have been synthesized and characterized. The crystal and molecular structures of
Co(Phca2en)Cl2 (2), Ni(Phca2en)Br2 (5) and Zn(Phca2en)Cl2 (6) were determined by X-ray crystallography from single-crystal data.
Complexes 2 and 5 are isomorph and isostructure, in which the coordination polyhedron about the central metal ion is distorted
tetrahedron with Cl/Co/Cl, 110.17(6)8; N /Co /N, 84.16(13)8 and Cl/Zn /Cl, 112.02(6)8; N /Zn/N, 83.45(16)8. The complex 5
crystallizes in triclinic system with two molecules per asymmetric unit, both having nickel ion in distorted tetrahedral geometry, Br /
Ni /Br, 122.645(18)8 and 125.729(18)8; N /Ni /N, 84.63(9)8 and 85.08(9)8. These structures consist of intermolecular hydrogen
bonds of the type C /H X. The formation of the C /H M weak intramolecular hydrogen bonds due to the trapping of C/H
bonds in the vicinity of the metal atoms are reported for 2, 5 and 6. A 1H NMR study of Zn complexes gives further evidence for the
presence of such interactions and their significance. The spectral properties of the above complexes are also discussed.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Schiff base complexes; Cobalt(II); Nickel(II); Zinc(II); Tetrahedral; Crystal structures
1. Introduction
Transition metal compounds containing the Schiff
base ligands have been of interest for many years [1 /4].
These complexes play an important role in the developing of coordination chemistry related to catalysis and
enzymatic reactions, magnetism and molecular architectures [5 /8]. Bidentate ligands containing imine
groups have also been used as the modulators of
structural and electronic properties of transition metal
centers [9]. Many MLX2 complexes of Co(II), Ni(II),
and Zn(II) with L /diimine have been investigated. In
spite of the diversity in the coordination environment
and the structure of these complexes, which depend on
the type of Schiff base and the anion, bulky ligands and/
or anions will force tetrahedral coordination [10 /15]. In
the course of our studies on transition metal Schiff base
complexes [16,17], we have synthesized and characterized a series of M(Phca2en)X2 complexes with a new
bidentate ligand Phca2en (/N ,N ?-bis(b-Phenyl-cinnamaldehyde)-1,2-diiminoethane) and X /halides or
pseudohalides (Scheme 1). The crystal structures of
Co(Phca2en)Cl2, Ni(Phca2en)Br2, and Zn(Phca2en)Cl2
complexes are presented here.
2. Experimental
Corresponding author. Tel.: /98-311-391-2351; fax: /98-311391-2350
E-mail address: [email protected] (M. Amirnasr).
All reagents were used as supplied by Aldrich and
Fluka without further purification. Solvents used for the
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 2 7 7 - 9
2734
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
Scheme 1.
reactions were purified and dried by conventional
methods [18].
2.1. Physical measurements
NMR spectra were obtained on a BRUKER
AVANCE DRX500 (500 MHz) spectrometer. Proton
chemical shifts d are reported in part per million (ppm)
relative to an internal standard of Me4Si, and the J
values are reported in Hertz. The UV /Vis spectra were
recorded on a Perkin/Elmer Lambda 9 spectrophotometer with quartz cells (1 cm path length). Elemental
analyses were performed by using Heraeus CHN-ORAPID elemental analyzer. IR spectra were recorded as
KBr pellets on a Shimadzu 435 spectrophotometer.
2.2. Synthesis
2.2.1. N ,N ?-bis(b-phenylcinnamaldehyde)-1,2diiminoethane, Phca2en (1)
To a solution of 2.08 g (10 mmol) b-phenylcinnamaldehyde in 25 ml ethanol, cooled in an ice bath, was
added dropwise 300 mg (5 mmol) of ethylenediamine.
The mixture was then stirred for an additional 2 h.
N ,N ?-bis(b-phenylcinnamaldehyde)-1,2-diiminoethane
(Phca2en) was obtained as a white microcrystalline
precipitate. The precipitate was filtered off, washed
with 5 ml cold absolute ethanol. Yield: 3.960 g (90%).
Anal . Calc. for C32H28N2: C, 87.28; H, 6.36; N, 6.36.
Found: C, 87.30; H, 6.35; N, 6.38%. IR (KBr, cm 1):
nmax 1614 (s, C /N). 1H NMR: d 3.68 (s, 4H, /CH2 /
CH2 /), 6.82 (d, 2H, Ph2C /CH /), 7.31 (m, 20H, ArH),
7.85 (d, 2H, /CH /N/). 13C NMR: d 61.52 (/
N13CH13
2 CH2N/), 126.72, 127.87, 128.15, 128.23,
128.35, 128.72, 130.31, 140.95, 151.73 (Ph13CH /),
163.01 ( /13C /N /).
2.2.2. [Co(Phca2en)Cl2] (2)
To a solution of Phca2en (440 mg, 1 mmol) in 10 ml
CH2Cl2 was added 130 mg (1 mmol) of anhydrous
CoCl2, and stirred at room temperature (r.t.) for 3 h
under nitrogen atmosphere. The reaction mixture was
filtered off. The volume of the solvent was reduced
under vacuum to about 1 ml. The diffusion of diethyl
ether vapor into the concentrated solution gave needle
like blue crystals suitable for X-ray studies. The crystals
were filtered off and washed with a mixture of diethyl
ether /dichloromethane (9:1 v/v), and dried in vacuo.
Yield: 456 mg (80%). Anal . Calc. for C32H28N2Cl2Co:
C, 67.41; H, 4.91; N, 4.91. Found: C, 67.42; H, 4.93; N,
4.90%. IR (KBr, cm1): nmax 1603 (s, C /N).
2.2.3. [Co(Phca2en)Br2] (3)
This complex was prepared in a similar manner to 2
using CoBr2 (218 mg, 1 mmol). Deep green crystals were
collected by filtration and dried in vacuo. Yield: 514 mg
(82%). Anal. Calc. for C32H28N2Br2Co: C, 58.31; H,
4.25; N, 4.25. Found: C, 58.33; H, 4.27; N, 4.26%. IR
(KBr, cm 1): nmax 1600 (s, C /N).
2.2.4. [Ni(Phca2en)Cl2] (4)
To a stirring solution of 129 mg (1 mmol) of
anhydrous NiCl2 in 20 ml acetonitrile was added
dropwise a solution of 440 mg (1 mmol) Phca2en in 10
ml acetonitrile, and refluxed for 30 min. The solvent was
evaporated on a rotatory evaporator at 40 8C under
reduced pressure. The solid residue was dissolved in 20
ml acetonitrile and filtered off. The filtrate was left
overnight under diffusion of diethyl ether to give pink/
red crystals. Yield: 415 mg (73%). Anal. Calc. for
C32H28N2Cl2Ni: C, 67.43; H, 4.91; N, 4.91. Found: C,
67.49; H, 4.90; N, 4.95%. IR (KBr, cm 1): nmax 1603 (s,
C /N).
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
2.2.5. [Ni(Phca2en)Br2] (5)
This complex was prepared in a similar manner to 4
using NiBr2 (218 mg, 1 mmol). Deep pink crystals were
collected by filtration and dried in vacuo. Yield: 501 mg
(76%). Anal . Calc. for C32H28N2Br2Ni: C, 58.34; H,
4.25; N, 4.25. Found: C, 58.37; H, 4.27; N, 4.26%. IR
(KBr, cm 1): nmax 1604(s, C /N).
2.2.6. [Zn(Phca2en)Cl2] (6)
To a solution of 136 mg (1 mmol) ZnCl2 in 10 ml
methanol was added a solution of 440 mg (1 mmol)
Phca2en in 5 ml methanol and stirred at r.t. for 3 h. The
product precipitated as a white microcrystalline powder
and collected by filtration. The crude product was
recrystallized from acetone to give white needle-shape
crystals. The crystals were collected by filtration and
dried in vacou. Yield: 529 mg (92%). Anal . Calc. for
C32H28N2Cl2Zn: C, 66.65; H, 4.85; N, 4.85. Found: C,
66.68; H, 4.86; N, 4.86%. IR (KBr, cm 1): nmax 1616(s,
C /N). 1H NMR: d 3.72 (s, 4H, /CH2 /CH2 /), 7.35 (m,
22H, Ph2C /CH /, ArH), 8.0 (d, 2H, JHH /9.78 Hz, /
CH /N/). 13C NMR: d 58.72 (/N13CH13
2 CH2N/),
124.45, 129.75, 129.86, 130.14, 130.47, 131.52, 131.72,
138.39,140.45, 161.48 (Ph13CH /), 168.91 ( /13C /N/).
2.2.7. [Zn(Phca2en)Br2] (7)
This complex was prepared in a similar manner to 6
using ZnBr2 (225 mg, 1 mmol). Yield: 578 mg (87%).
Anal. Calc. for C32H28N2Br2Zn: C, 57.75; H, 4.21; N,
4.21. Found: C, 57.77; H, 4.20; N, 4.21%. IR (KBr,
cm 1): nmax 1615 (s, C /N). 1H NMR: d 3.72 (s, 4H, /
CH2 /CH2 /), 7.36 (m, 22H, Ph2C /CH /, ArH ), 8.01(d,
2H, JHH /9.82 Hz, /CH /N/). 13C NMR: d 58.65 ( /
N13CH13
2 CH2N/), 124.37, 129.75, 129.89, 130.19,
130.48, 131.54, 131.75, 138.38, 140.48, 161.53
(Ph13CH /), 168.80 (/13C /N/).
2735
was precipitated as a white microcrystalline powder and
collected by filtration and dried in air. Yield: 528 mg
(85%). Anal . Calc. for C34H28N4S2Zn: C, 61.80; H, 4.50;
N, 4.50. Found: C, 61.85; H, 4.52; N, 4.51%. IR (KBr,
cm 1): nmax 1603 (s, C /N), 2055 (s, NCS). 1H NMR: d
3.67 (s, 4H, /CH2 /CH2 /), 6.99 (d, 2H, JHH /9.80 Hz,
Ph2C /CH /) 7.36 (m, 20H, ArH), 8.02 (d, 2H, JHH /
9.80 Hz, /CH /N/). 13C NMR: d 58.75 ( /
N13CH13
2 CH2N/), 123.47, 129.88, 130.00, 130.12,
130.44, 130.95, 131.65, 132.26, 138.12, 140.15, 163.75
(Ph13CH /), 170.07 ( /13C /N /).
2.3. X-ray crystallography
Suitable single crystals of [Co(Phca2en)Cl2] (2),
[Ni(Phca2en)Br2] (5), and [Zn(Phca2en)Cl2] (6), were
obtained by diffusion of diethyl ether vapor into the
dichloromethane solution of 2 and acetonitrile solution
of 5 or by slow evaporation of an acetone solution of 6
at r.t. Data were collected on a Siemens SMART CCD
diffractometer using graphite-monochromated Mo Ka
(l/0.71073 Å) radiation. For each crystals, a full
sphere of reciprocal lattice was scanned by 0.38 steps
in v with a crystal-to-detector distance of 3.97 cm.
Preliminary orientation matrices were obtained from the
first frames using SMART [19]. The data were empirically
corrected for absorption and other effects using SADABS
[20]. The structures were solved by direct methods and
refined by the full-matrix least-squares method on F2
data using the SHELXTL [21]. All non-H atoms were
refined anisotropically. The H atoms were constrained
to idealized geometries and refined isotropically.
3. Results and discussion
3.1. Synthesis
2.2.8. [Zn(Phca2en)I2] (8)
This complex was prepared in a similar manner to 6
using ZnI2 (319 mg, 1 mmol). Yield: 637 mg (84%).
Anal . Calc. for C32H28N2I2Zn: C, 50.60; H, 3.69; N,
6.39. Found: C, 50.48; H, 6.37; N, 6.37%. IR (KBr,
cm 1): nmax 1614 (s, C /N). 1H NMR: d 3.72 (s, 4H, /
CH2 /CH2 /), 7.37 (m, 20H, ArH), 7.57 (d, 2H, JHH /
9.83 Hz, Ph2C /CH /), 8.02 (d, 2H, JHH /9.83 Hz, /
CH /N/). 13C NMR: d 58.49 (/N13CH13
2 CH2N/),
124.28, 129.77, 129.93, 130.29, 130.53, 131.55, 131.78,
138.35, 140.60, 161.39 (Ph13CH /), 168.51 (/13C /N/).
2.2.9. [Zn(Phca2en)(NCS)2] (9)
To a solution of 261 mg (1 mmol) Zn(NO3)2 in 10 ml
ethanol was added a solution of 194 mg (2 mmol) of
KSCN in 5 ml ethanol and stirred for 20 min. The
resulting white KNO3 salt was filtered off and a solution
of 440 mg (1 mmol) of Phca2en in 5 ml methanol was
added to the filtrate and stirred for 30 min. The product
Phca2en was prepared by the condensation of bPhenylcinnamaldhyde with ethylenediamine. The product, as a white solid material, was characterized by IR,
UV /Vis and 1H, 13C NMR spectroscopy.
The cobalt complexes were prepared by reacting
equimolar quantities of the anhydrous cobalt halides
salts and Phca2en in dichloromethane. These complexes
are stable in air in the solid state. The stability of cobalt
complexes in solution depends on the solvent used. The
compounds are stable in dichloromethane for at least 24
h, while they are much less stable in methanol. A
methanolic solution in open air slowly turns brown in
6 h. To avoid any oxidation of the cobalt complexes, the
synthesis of 2 and 3 were carried out under nitrogen
atmosphere.
The nickel complexes were prepared by reacting
equimolar quantities of the anhydrous nickel halides
salts and Phca2en in boiling acetonitrile. The zinc
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M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
complexes were prepared by reacting equimolar quantities of anhydrous zinc salts and Phca2en in dichloromethane. The zinc complexes are colorless solids
dissolving in chloroform, methanol, ethanol and acetone
and they are stable at ambient conditions.
3.2. Spectral studies
All complexes show similar IR spectral features,
exhibiting a strong band between 1600 and 1616 cm 1
corresponding to n(C /N). This band is shifted to the
lower frequencies by 6/20 cm 1 relative to the free
ligand upon the coordination of the nitrogen atoms. The
observation of a strong band at 2065 cm 1 in the IR
spectrum of complex 9 indicates that the NCS ligand in
this complex is most probably N-bonded [22].
The 1H NMR data of the Phca2en suggest that the
ligand has a symmetrical structure with Ha and Hb
protons (Scheme 1) in trans positions (J /9.5 Hz). The
four methylene protons appear as a singlet at 3.68 ppm.
The two vinyl CH protons (Hb) are observed as a
doublet centered at 6.82 ppm, and the multiplet centered
at 7.31 ppm is assigned to the phenyl protons. The two
H /C /N protons (Hb) appear as a doublet at 7.85 ppm.
In the 1H NMR spectra of compounds 6/9, the
hydrogen of the imine CH groups (Ha) exhibits a
downfield shift relative to the free ligand and shows
no significant difference by changing the anion. Nevertheless, the signals due to Hb protons appear at 7.35,
7.36, 7.57 and 6.99 ppm for ZnLCl2, ZnLBr2, ZnLI2 and
ZnL(NCS)2, respectively (Fig. 1). In search for an
explanation for this behavior, we have found no
interaction between Hb and the chloride atoms in
ZnLCl2. However, the observed variation in the Hb
chemical shifts could be attributed to an intramolecular
interaction with metal atom in the form of C /H Zn
weak hydrogen bonds (see more details in the crystal
structures). Such interactions have also been reported by
others [23,24]. The extent of interaction depends on the
steric restrictions imposed by the coordinated anion and
the electron density of metal atom. The shielding effect
resulting from this intramolecular interaction is strongest for Cl followed by Br and I and to a greater extent
for NCS coordinated to the metal atom.
The 13C NMR spectrum of the free ligand exhibits 12
signals due to the fact that the two phenyl rings (exo and
endo ) are in different position relative to the ethylenic
protons (trans and cis ), and each phenyl ring has the its
own characteristic signals. In the 13C NMR spectra of
the complexes 6 /9, the carbon atoms adjacent to the
donor nitrogen atoms show downfield shift in their
positions as compared with the free ligand, clearly
indicating the coordination of the ligand and retention
of the structure in the chloroform solutions.
The UV /Vis spectral data of M(Phca2en)X2 complexes are presented in Table 1. The Co(Phca2en)Cl2
show three closely spaced weak bands in the visible
region and a very intense band in the UV region. In the
regular tetrahedral and near-tetrahedral Co(II) complexes only one d /d transition [4A2(F)0/4T1(P), assigned as y3] is observed in the visible region. This
transition has been reported for the tetrahedral [Co(NCS)4]2 at 615 nm and for the pseudotetrahedral
[Co(morpholine)2(NCS)2] at 616 nm [25]. The three
Fig. 1. 1H NMR spectrum of [Zn(Phca2en)I2] (8).
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
Table 1
UV /Vis spectral data of M(Phca2en)X2 complexes
UV /Vis lmax (nm) (log o (M 1
cm 1))
Compound
Solvent
Phca2en (1)
Co(Phca2en)Cl2 (2)
chloroform 330(4.73)
chloroform 651(2.77), 633(2.79), 580(3.08),
342(4.59)
chloroform 649(3.00), 602(3.00), 578(2.67),
350(4.57)
chloroform 499(2.20), 320(4.65)
chloroform 514(2.29), 330(4.68)
chloroform 329.5(4.75)
chloroform 331(4.71)
chloroform 332(4.72)
chloroform 335(4.70)
Co(Phca2en)Br2 (3)
Ni(Phca2en)Cl2 (4)
Ni(Phca2en)Br2 (5)
Zn(Phca2en)Cl2 (6)
Zn(Phca2en)Br2 (7)
Zn(Phca2en)I2 (8)
Zn(Phca2en)(NCS)2
(9)
closely spaced transitions in the spectrum of Co(Phca2en)X2 complexes arise from the distortion in the
tetrahedral symmetry around the metal center. This
splitting originates from the reduction of the orbital
degeneracy due to the difference in the ligand field
strength of imine and halides donor atoms and the
restricted bite angle of the N(1) /M /N(2) chelating
ligand [25,26]. The intensity of the UV-band is consistent with its being a ligand-centered p 0/p transition or/
and a charge-transfer transition.
The 3T1(F) 0/3T1(P) transition [27] in Ni(Phca2en)X2
complexes (4, 5), appears as a low intensity band at 514
nm which is similar to that reported for Ni(Me4propylenediamine)2Cl2 (512 nm) [25]. A strong band at 330
nm is assigned to a ligand-centered p 0/p transition or/
and a charge-transfer transition. The electronic spectral
data conform with the structures determined by X-ray
crystallography for cobalt and nickel complexes.
The electronic absorption spectra of the
Zn(Phca2en)X2 complexes (6 /9) in chloroform, are
dominated by the broad band in the region 320 nm
corresponding to the intra-ligand transition of Phca2en
or/and a charge-transfer transition. No d /d transition
are expected for d10 Zn(II) complexes.
3.3. Crystal and molecular structure of 2, 5 and 6
The crystallographic and refinement data are summarized in Table 2 and the selected bond distances and
angles are given in Table 3. The molecular structures of
2, 5 and 6 are illustrated in Figs. 2 and 3, respectively,
where metal atoms are coordinated by the bidentate
Schiff base ligand and two halogen atoms. Our results
show that 2 and 6 are isomorph and isostructure. While
a tetrahedral geometry might be expected for a fourcoordinated M(II) center, the geometry about M(II) in
2, 5 and 6 is distorted by the restricting bite of chelating
ligand. Considering a low structural preference energy
for other geometries of d7 and d10 ions, a distorted
tetrahedral structure can be inferred for other Co(Ph-
2737
ca2en)X2 and Zn(Phca2en)X2 complexes and most
probably for Ni(Phca2en)X2 complexes as well.
For 2 (see Fig. 2), the N(1) /Co /N(2) angle is only
84.07(15)8 being in the range of 828 /898 found for
ethylenediamine chelated complexes [28 /30]. This angle
is fixed by the bite size of the ligand (N(1) N(2) /
2.737(1) Å). The Cl(1)/Co /Cl(2) angle is 110.17(6)8 but
the Cl(1) /Co /N(2) angle, 117.27(12)8, is larger than the
tetrahedral values. The average Co /Cl bond length of
2.22 Å agrees well with the same distance in other
tetrahedral cobalt complexes: Co(ethylenedimorpholine)Cl2, 2.23 Å; Co(p -toluidine)2Cl2, 2.26 Å; Co(bdmpab)Cl2, 2.23 Å. The Co /Nav of 2.0483 Å is being
normal [29 /33]. The Co(II) complexes with bidentate
Schiff bases showing a distorted tetrahedral structure,
are common both in solid state and in solution (of noncoordinating solvents) [34 /36] and the observed pseudotetrahedral structure for Co(Phca2en)Cl2 (2) is in
accordance with this expectation.
The compound Ni(Phca2en)Br2 crystallizes with two
molecules per asymmetric unit (molecule A and B)
showing some conformational differences (see Fig. 3).
Nickel complexes with bidentate chelating ligands
including Schiff-bases often prefer tetragonal geometries
[29,30]. However, the steric effects from Phca2en distort
the geometry at Ni(II) in Ni(Phca2en)Br2, (5), to
pseudotetrahedral (Fig. 4). The angles N(1) /Ni /N(2),
84.63(9)8 (A) and 85.08(9)8 (B), and Br(1) /Ni /Br(2),
122.645(18)8 (A) and 125.729(18)8 (B), are indicative of
a large deviation from idealized tetrahedral symmetry
that is similar for those found in Ni(C20H24N2)Br2 [23]
and Ni(biq)Br2 [37].
The Ni /Br average bond length of 2.34 Å agrees with
those reported for other tetrahedral nickel complexes:
[Ni(PPh3)2Br2], 2.34 Å [38,39]; [(n -C4H9)4N][Ni(C9H7N)Br3], 2.38 Å [25] and Ni(biq)2Br2, 2.34 Å
[37]. The average Ni /N distances of 1.99 Å are similar
to those found in the pseudotetrahedral bis(N -isopropylsalicylaldiminato)nickel(II), 1.97 Å [40,41] and Ni(II)
imine complexes, (Ni(biq)2Br2 1.99 Å [37] and [Ni(TC6,6)] 1.95 Å), [42], but they are approximately 0.07 Å
longer than those for tetragonal Ni(II) analogues
[43,44]. In the tetragonal case, the dx2/y2 orbital is
vacant, allowing ligands to approach to the metal along
the x and y axes.
The Zn(II) in 6 adopts a pseudotetrahedral coordination (see Fig. 2), where the tetrahedron is somewhat
distorted by a small N(1) /Zn /N(2) angle being
83.45(16)8. The Cl(1) /Zn /Cl(2) angle has opened up
to 112.02(6)8. The average Cl /Zn /N angle of 114.678 is
also larger than the tetrahedral value. The Zn /N
distance ranging from 2.078(4) to 2.066(4) Å are
considered normal and comparable for those for 2 and
5. The average Zn /Cl distance of 2.22 Å agree well with
normal Zn /Cl bond distances [24].
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
2738
Table 2
Crystallographic data for compound 2, 5 and 6
Compound
Co(Phca2en)Cl2 (2)
Ni(Phca2en)Br2 (5)
Zn(Phca2en)Cl2 (6)
Empirical formula
Formula weight
T (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a (8)
b (8)
g (o)
V (Å3)
Z , Dcalc (g cm 3)
m (mm 1)
F (000)
Index ranges
C32H28Cl2N2Co
570.39
297(2)
monoclinic
P 21/n (No. 14)
10.4102(3)
15.3333(4)
18.6290(4)
90
101.149(1)
90
2917.49(13)
4, 1.299
0.794
1180
115 h 5 11; 175 k 5 17;
205 l 5 20
18 181
4176
0.037
4176/334
1.147
0.062/0.168
C32H28Br2N2Ni
659.09
183(2)
triclinic
P/1̄ (No. 2)
7.9336(1)
15.9184(1)
23.9192(1)
96.802(1)
96.106(1)
100.166(1)
2927.27(4)
4, 1.496
3.415
1328
95 h 5 9; 19 5 k 5 19;
295 l 5 26
34 184
11 921
0.038
11 921/667
1.064
0.033/0.080
C32H28Cl2N2Zn
576.83
183(2)
monoclinic
P 21/n (No. 14)
10.3083(1)
15.3555(1)
18.5743(2)
90
101.460(1)
90
2881.49(5)
4, 1.330
1.061
1192
125 h 5 12; 185 k 5 18;
225 l 5 22
30 770
5266
0.080
5266/334
1.042
0.062/0.137
0.072/0.175
1.314/0.290
0.050/0.092
0.525/0.721
0.094/0.154
1.453/1.092
Reflections collected
Independent reflection
R (int)
Data/parameters
Good-of-fit on F
R1/wR2 a for observed reflection
[I 2s (I )]
R1/wR2 for all data
Largest resolution peak/hole
(e Å 3)
a
R1 ajjFojjFcjj/ajFoj, wR2 {a[w (Fo2Fc 2)2]/a[w (Fo2)2]}1/2.
Table 3
Selected bond distances (Å) and angles (o) for compound 2, 5 and 6
M, X
2
5
6
Co, Cl
Ni, Br
Zn, Cl
Molecule A
Molecule B
Bond distances
M N1
2.047(4)
M N2
2.048(4)
M X1
2.2187(15)
M X2
2.2358(14)
2.007(2)
1.985(2)
2.3673(4)
2.3264(4)
1.998(8)
1.988(2)
2.3578(4)
2.3325(4)
2.078(4)
2.066(4)
2.2168(14)
2.2310(14)
Bond angles
N1 M N2
N1 M X1
N2 M X1
N1 M X2
N2 M X2
X1 M X2
C3 N1 M
C4 N1 M
C6 N2 M
C5 N2 M
84.63(9)
105.42(6)
104.45(7)
114.81(7)
117.89(6)
122.645(18)
132.53(19)
107.90(16)
129.85(19)
110.37(16)
85.08(9)
102.89(7)
105.89(6)
116.81(7)
112.63(9)
125.729(18)
130.44(19)
109.51(16)
132.08(19)
109.28(16)
83.45(16)
110.66(12)
115.85(11)
118.52(11)
113.68(12)
112.02(6)
135.0(4)
107.6(3)
135.0(4)
107.6(3)
84.07(15)
110.66(12)
117.27(12)
119.83(12)
113.02(12)
110.17(6)
134.7(3)
107.8(3)
135.5(4)
107.5(3)
The ligand adopts a Z ,Z configuration in these
complexes. The mean value for dihedral angles N /C /
C /C is about 177.58 indicating the planarity of this
moiety for the complexes studied here. However, the N /
C /C /C moieties in each complex are not coplanar, but
showing parallel configuration. The single bond distance
C(2) /C(3) in 2, 5, and 6 (1.42, 1.43 /1.44 and 1.42 Å,
respectively) being slightly shorter than C(4) /C(5) in 2,
5 and 6 (1.518, 1.523 /1.528 and 1.524 Å, respectively)
indicating an extended electron delocalization in these
complexes. Torsion angles in the chelating ring and the
stiryl moieties are listed in Table 4. In comparison to the
exo-phenyl rings, the planes of the endo -phenyl rings are
more parallel to the planes defined by the C /C /N
groups. This result demonstrates that p delocalization in
the stiryl moiety is solely between the endo -phenyl rings
and the chain connecting the rings to the coordinated
nitrogen atoms.
Despite the fact that the donor nitrogen atoms are sp2
hybridized, the chelate ring is significantly puckered in
all three complexes and some strain in the chelate ring is
suggested by the deviation from 1208 angle about the
nitrogen, Co /N(1) /C(3) (134.7(3)8) and Co /N(1) /C(4)
(107.8(3)8)
in
2;
Ni /N(1) /C(3)
(132.53(19)8,
130.44(19)8)
and
Ni /N(1) /C(4)
(107.90(16)8,
109.51(16)8) in 5; Zn /N(1) /C(3) (135.0 (4)8) and Zn /
N(1) /C(4) (107.6(3)8) in 6. The dihedral angles N(1) /
C(4) /C(5) /N(2) are /56.8(5)8 in 2, /51.9(3)8 and
50.1(3)8 in 5 and /56.3(5)8 in 6 that is typical for
diamine chelate [30,45,46].
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
2739
Fig. 2. Representation of molecular structure of 2 with atom-labeling scheme. Atomic displacement parameters are shown at 50% probability level.
The crystal structure of [ZnCl2(Phca2en)] (6) is visually indistinguishable from that of the cobalt compound and uses an identical atom numbering
scheme, but with ‘Co’ replaced by ‘Zn’.
The geometry of hydrogen bonds are given in Table 5.
Complexes 2 and 6 exhibit similar hydrogen bonding
patterns built up from the C /H Cl hydrogen bonds.
Chains of MLCl2 molecules arranged along a axis are
linked together via C /H Cl hydrogen bonds to form
three-dimensional networks (Fig. 4(a and b)). The
H Cl contacts range from 2.63 to 2.83 Å with the
C /H Cl angles of 1348/1678. For complex 5, the C /
H Br hydrogen bonds have minor impact on crystal
packing, though a three-dimensional hydrogen bonding
network exists. The H Br contacts are as large as 3.01
Å and the mean C /H Br angle being 1398 reflecting
the weakness of such intermolecular interactions in the
solid state.
Due to the geometrical restrictions in 2, 5 and 6, the
Hb atoms, i.e. H(2) and H(7), lie in the vicinity of the
metal atoms making intramolecular interactions possible in the form of weak C /H M hydrogen bonds. This
type of interaction is somewhat similar to the agostic
interactions found in many organometallic complexes
[47,48], although a C /Hd Md charge-assisted hydrogen bonding could be encountered here. As a matter
of fact, the involvement of the metal centers in hydrogen
bonding is now well established and known as nontraditional hydrogen bonds [49,50]. A recent survey by
Desiraju and Steiner [51], gives the range 2.5 /3.2 Å for
the weak (C /)H M hydrogen bonds. Our structural
data reveals that the (C /)H M interactions ranging
from 2.9 to 3.13 Å in 2, 5 and 6 would meet the above
criteria and can be regarded as intramolecular weak
hydrogen bonds. Consequently, the Hb atoms are
influenced by the change in the electron density on the
central metal atom and this can be followed easily by 1H
NMR spectroscopy. Our results from 1H NMR study of
Zn(Phca2en)X2 complexes, in which X /Cl, Br, I and
NCS, clearly give further evidence to the existence of
Fig. 3. Representation of molecular structure of 5 with atom-labeling scheme. Atomic displacement parameters are shown at 50% probability level.
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
2740
Fig. 4. The C/H Cl hydrogen bonds are forming chains (a) of CoLCl2 (or ZnLCl2) molecules along a axis in the crystal structure of 2 (or 6) and a
three-dimensional network (b) is built up from linking chains.
Table 4
Torsion angles for chelating ring and stiryl groups
2
5
tion has also been reported by others [52,24] for closely
related structures.
6
Molecule A Molecule B
4. Supplementary material
N1 C4 C5 N2
56.3(5) 51.9(3)
N1 C3 C2 C1
178.4(5)
178.9(3)
N2 C6 C7 C8
175.5(5) 179.3(3)
C2 C1 C21 C22
35.4(8)
157.2(3)
C2 C1 C11 C12 129.3(6)
121.6(3)
C7 C8 C31 C32
39.5(7)
18.9(4)
C7 C8 C41 C42
48.1(8)
63.7(4)
50.1(3)
178.9(3)
174.7(3)
36.4(4)
129.7(3)
40.4(4)
43.3(4)
56.8(5)
177.5(5)
176.6(5)
34.9(8)
133.6(7)
39.3(7)
48.0(8)
such (C /)H Zn intramolecular interactions, although
being weak but can be significant. This type of interac-
Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited
with the Cambridge Crystallographic Centre as supplementary publication no. CCDC- 182874 (2), 182875 (5)
and 182876 (6). Copies of the data can be obtained free
of charge on application to The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: /441223-336033; e-mail: [email protected] or www:
http://www.ccdc.cam.ac.uk).
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
Table 5
Intra- and intermolecular hydrogen bonds for 2, 5 and 6 (Å, 8)
D H A
d(D H) d(H A)
d(D A)
B (DHA)
2
C2 H2 Co
C7 H7 Co
C5 H5A Cl1a
C16 H16 Cl1a
C34 H34 Cl1b
C4 H4A Cl2c
C42 H42 Cl2c
0.95
0.95
0.97
0.93
0.93
0.97
0.93
3.13
3.13
2.79
2.65
2.78
2.83
2.81
3.538(1)
3.538(1)
3.593(5)
3.560(6)
3.587(8)
3.585(5)
3.685(6)
103
103
141
166
145
136
157
5
C2A H2A NiA
C7A H7A NiA
C2B H2B NiB
C7B H7B NiB
C12B H12B Br2Aa
C42B H42B Br1A
C12A H12A Br2Bb
0.95
0.95
0.95
0.95
0.95
0.95
0.95
3.00
2.92
2.91
3.02
2.93
2.90
3.01
3.427(2)
3.357(2)
3.361(2)
3.430(2)
3.703(3)
3.695(3)
3.736(3)
106
144
142
142
140
142
135
6
C2 H2 Zn
C7 H7 Zn
C4 H4a Cl2a
C5 H5A Cl1b
C16 H16 Cl1b
C34 H34 Cl1c
C42 H42 Cl2a
0.95
0.95
0.99
0.99
0.95
0.95
0.95
3.12
3.13
2.80
2.76
2.63
2.77
2.76
3.547(1)
3.550(1)
3.552(5)
3.564(5)
3.561(6)
3.580(7)
3.658(5)
102
103
134
139
167
143
157
Symmetry codes: (2); a) x1, y , z , b) x1/2, y1/2,
z1/2; (5); a) x , y1, z , b) x , y1, z ; (6); a) x1, y1, z ,
b) x2, y1, z , c) x3/2, y1/2, z1/2.
Acknowledgements
Authors wish to thank the Division of Inorganic
Chemistry, Department of Chemistry, Göteborg University for providing X-ray structure determination
facilities. M.A. and S.D. would like to acknowledge
the Isfahan University of Technology and Tarbiat
Modarres University Research Council for partial support of this work.
References
[1] S. Yamada, Coord. Chem. Rev. 190 /192 (1999) 537.
[2] S. Chang, L. Jones, C.M. Wang, L.M. Henling, R.H. Gruubbs,
Organometallics 17 (1998) 3460.
[3] K.K. Chaturvedl, J. Inorg. Nucl. Chem. 39 (1977) 901.
[4] R.D. Archer, B. Wang, Inorg. Chem. 29 (1990) 39.
[5] J. Costamagna, J. Vargas, R. Latorre, A. Alvarado, G. Mena,
Coord. Chem. Rev. 119 (1992) 67.
[6] S.C. Bhatia, J.M. Bindlish, A.R. Saini, P.C. Jain, J. Chem. Soc.,
Dalton Trans. (1981) 1773.
[7] J.M. Bindlish, S.C. Bhatia, P.C. Jain, Indian J. Chem. 13 (1975)
18.
[8] J.M. Bindlish, S.C. Bhatia, P. Gautam, P.C. Jain, Indian J.
Chem., Sect. A 16 (1978) 279.
[9] M.T. Miller, P.K. Gantzel, T.B. Karpishin, Inorg. Chem. 38
(1999) 3414.
[10] R.J. Butcher, E. Sinn, Inorg. Chem. 16 (1977) 2334.
2741
[11] S.S. Tandon, S. Chander, L.K. Thompson, Inorg. Chim. Acta
300-302 (2000) 638.
[12] E. Quiroz-Castro, S. Bernes, N. Barba-Behrens, R. TapiaBenavids, R. Contreras, H. Noth, Polyhedron 19 (2000) 1479.
[13] H.L. Blonk, W.L. Driessen, J. Reedijk, J. Chem. Soc., Dalton
Trans. (1985) 1699.
[14] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson,
R. Taylor, J. Chem. Soc., Dalton Trans. (1985) S1.
[15] Z. Dori, H.B. Gray, J. Am. Chem. Soc. 88 (1966) 1394.
[16] M. Amirnasr, K.J. Schenk, A. Gorji, R. Vafazadeh, Polyhedron
20 (2001) 695.
[17] M. Amirnasr, R. Vafazadeh, Sci. Iranica 4 (1997) 35.
[18] D.D. Perrin, W.L. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, 2nd ed., Pergamon, New York, 1990.
[19] ‘SMART and SAINT: Area Detector Control and Integration
Software’, Siemens Analytical X-ray Instruments Inc., Madison,
WI, 1995.
[20] G.M. Sheldrick, SADABS: Program for Empirical Absorption
Correction of Area Detectors, University of Göttingen, Germany,
1996.
[21] ‘SHELXTL (Version 5.10)’, Bruker AXS Inc., Madison, WI, 1997.
[22] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Complexes, fourth ed., Wiley, New York, 1992.
[23] D. Johnston, W.L. Rohrbuagh, W.D. Horrockas, Jr., Inorg.
Chem. 10 (1971) 574.
[24] P. Li, I.J. Scowen, J.E. Davies, M.A. Halcrow, J. Chem. Soc.,
Dalton Trans. (1998) 3791.
[25] A.B.P. Lever, Inorganic Electronic Spectroscopy, 2nd ed., Elsevier, Amsterdam, 1984, p. 496.
[26] N. Greenwood, A. Earnshaw, Chemistry of the Elements
(Chapter 26), Pergamon, Oxford, 1984.
[27] C.A. Otter, S.M. Couchman, J.C. Jeffery, K.L.V. Mann, E.
Psillakis, M.D. Ward, Inorg. Chim. Acta 278 (1998) 178.
[28] W.D. Horrocks, Jr., D.H. Templeton, A. Zalkin, Inorg. Chem. 7
(1968) 2303.
[29] J.R. Wiesner, E.C. Lingafelter, Inorg. Chem. 5 (1966) 1770.
[30] W.R. Scheidt, J.C. Hanson, P.G. Rasmussen, Inorg. Chem. 8
(1969) 2398.
[31] H.I. Blonk, W.L. Driessen, J. Reedijk, J. Chem. Soc., Dalton
Trans. (1985), 1699.
[32] Y. Yamamoto, T. Suzuki, S. Kaizaki, J. Chem. Soc., Dalton
Trans. (2001) 1566.
[33] Y. Yamamoto, T. Suzuki, S. Kaizaki, J. Chem. Soc., Dalton
Trans. (2001) 2943.
[34] B.O. West, J. Chem. Soc. (1962) 1374.
[35] L. Sacconi, M. Ciampolini, F.P. Cavasino, J. Am. Chem. Soc. 84
(1962) 3246.
[36] R.H. Holm, G.W. Evervtt, A. Chakravorty, Prog. Inorg. Chem. 7
(1966).
[37] R.J. Butcher, E. Sinn, Inorg. Chem. 16 (1977) 2334.
[38] Y.P. Tian, C.Y. Duan, Z.L. Lu, X.Z. You, X.Y. Huang, J. Coord.
Chem. 38 (1996) 219.
[39] J.A.J. Jarvis, R.H.B. Mais, P.G. Owston, J. Chem. Soc. A (1968)
1473.
[40] J.L. deBoer, D. Rogers, A.C. Skapski, P.G.H. Troughton, Chem.
Commun. (1966) 756.
[41] M.R. Fox, P.L. Orioli, E.C. Lingafelter, L. Sacconi, Acta
Crystallogr. 17 (1964) 1159.
[42] W.M. Davis, M.M. Roberts, A. Zask, K. Nakanishi, T. Nozoe,
S.J. Lipard, J. Am. Chem. Soc. 107 (1985) 3864.
[43] S. Knapp, T.P. Keenan, X. Zhang, R. Fikar, J.A. Potenza, H.J.
Schugar, J. Am. Chem. Soc. 112 (1990) 3452.
[44] Y. Elerman, A. Elmali, I. Svoboda, H. Fuess, Acta Crystallogr.,
Sect. C 54 (1998) 1076.
[45] Y. Satio, H. Iwasaki, Bull. Chem. Soc. Jpn. 39 (1966) 92.
[46] C.F. Liu, J.A. Ibers, Inorg. Chem. 9 (1962) 773.
2742
M. Amirnasr et al. / Polyhedron 21 (2002) 2733 /2742
[47] M. Brookhart, M.L.H. Green, L.L. Wang, Prog. Inorg. Chem. 30
(1988) 1.
[48] R.H. Crabtree, Angew. Chem., Int. Ed. Engl. 32 (1993) 789.
[49] D. Braga, F. Grepioni, G.R. Desiraju, Chem. Rev. 98 (1988)
1375.
[50] D. Braga, F. Grepioni, E. Tedesco, K. Biradha, G.R. Desiraju,
Organometallics 16 (1987) 1846.
[51] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bonds in
Structural Chemistry and Biology, Oxford University Press,
New York, 1999.
[52] D.L. Johnston, W.L. Rohrbaugh, W.D. Horrocks, Jr., Inorg.
Chem. 10 (1971) 547.