Synthesis and structures of zinc(II) and cadmium(II) complexes with (η6-Benzenecarboxylate) chromium tricarbonyl and pyrazole derivatives

Article abstract of DOI:10.1002/zaac.201100269

Abstract. Reaction of zinc acetate with four different substituted pyrazoles (3,5-dimethyl pyrazole (3,5-Me₂PzH), 3,5-di-tert-butyl pyrazole (3,5-tBu₂PzH), 3,5-diphenyl pyrazole (3,5-Ph ₂PzH), and 5-methyl-3-phenyl pyrazole (3-Ph-5-Me-PzH)) followed by treatment with(η⁶-benzenecarboxylic acid) chromium tricarbonyl afforded the bimetallic zinc-chromium complexes [Zn{(η⁶-C ₆H₅COO)Cr(CO)₃}₂(3,5-Me ₂PzH)₂], [Zn{(η⁶-C₆H ₅COO)Cr(CO)₃}₂(3,5-tBu₂PzH) ₂], [Zn{(η⁶-C₆H₅COO)Cr(CO) ₃}₂(3,5-Ph₂PzH)₂], and [Zn{η⁶-C₆H₅COO)Cr(CO)₃} ₂(3-Ph-5-Me-PzH)₂]. The corresponding bimetallic cadmium-chromium complexes [Cd{(η⁶-C₆H ₅COO)Cr(CO)₃}₂(3,5-Me₂PzH) ₂] and [Cd{(η⁶-C₆H₅COO)Cr(CO) ₃}₂(3,5-tBu₂PzH)₂] were obtained by using cadmium acetate as starting material. The pyrazole rings and the carboxylate {(η⁶-C₆H₅COO)Cr(CO) ₃}^- anion act as monodentate ligand in the zinc complexes, whereas a monodentate and bidentate coordination of the {(η⁶- C₆H₅COO)Cr(CO)₃}^- anion is observed in the cadmium complexes. Copyright

Full text of DOI:10.1002/zaac.201100269

ARTICLE
DOI: 10.1002/zaac.201100269
Synthesis and Structures of Zinc(II) and Cadmium(II) Complexes with
(η6-Benzenecarboxylate) Chromium Tricarbonyl and Pyrazole Derivatives
Balasubramanian Murugesapandian[a] and Peter W. Roesky*[a]
In Memory of Professor Kurt Dehnicke
Keywords: Zinc; Chromium; Cadmium; Pyrazoles; Bimetallic compounds
Abstract. Reaction of zinc acetate with four different substituted pyr-
Cr(CO)3}2(3-Ph-5-Me-PzH)2]. The corresponding bimetallic cadmium-
azoles (3,5-dimethyl pyrazole (3,5-Me2PzH), 3,5-di-tert-butyl pyrazole chromium complexes [Cd{(η6-C6H5COO)Cr(CO)3}2(3,5-Me2PzH)2]
(3,5-tBu2PzH), 3,5-diphenyl pyrazole (3,5-Ph2PzH), and 5-methyl-3- and [Cd{(η6-C6H5COO)Cr(CO)3}2(3,5-tBu2PzH)2] were obtained by
phenyl pyrazole (3-Ph-5-Me-PzH)) followed by treatment with
(η6-benzenecarboxylic acid) chromium tricarbonyl afforded the bimetal- carboxylate {(η6-C6H5COO)Cr(CO)3}– anion act as monodentate ligand
lic zinc-chromium complexes in the zinc complexes, whereas a monodentate and bidentate coordina-
[Zn{(η6-C6H5COO)Cr(CO)3}2-
(3,5-Me2PzH)2],
using cadmium acetate as starting material. The pyrazole rings and the
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5-tBu2PzH)2], tion of the {(η6-C6H5COO)Cr(CO)3}– anion is observed in the cadmium
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5-Ph2PzH)2], and [Zn{η6-C6H5COO)
complexes.
oxylate complexes [(η5-C5H5)2TiX{(μ-O2CC6H5)Cr(CO)3}] (X
= Cl, Br, CH3) and [(η5-C5H5)2M(μ-O2CC6H5)Cr(CO)3]2 (M =
Ti, Zr) were known.[20] Recently, Long and co-workers re-
ported on the synthesis of [Zn4O{(η6-1,4-benzenedicarboxyl-
ate)Cr(CO)3}], which is a porous metal-organic framework.[21]
Under photolysis conditions substitution of a single CO ligand
per metal by N2 and H2 was observed. This kind of reactivity
was also observed in the discrete complexes.[22]
Herein we report on the reaction of [{η6-C6H5COOH}-
Cr(CO)3] with zinc acetate or cadmium acetate in the presence
of various pyrazole-based ancillary ligands. Pyrazole ligands
were extensively used in biology and coordination chemis-
try.[23] These ligands have been employed as ancillary ligands
for soluble multimetallic clusters constructed by phosphonic
acid[24] or carboxylic acid.[25] Zinc complexes containing pyr-
azole ligands were shown to mimic the biological activity of
carbonic anhydrase.[26] There are some examples of zinc and
cadmium carboxylate containing pyrazole ligands in the litera-
ture[27] but there were to the best of our knowledge no exam-
ples of zinc complexes containing organometallic carboxylic
acid ligands reported.
Introduction
Bi- and multimetallic compounds play a major role in bio-
chemistry[1] and heterogeneous catalysis.[2] These kinds of
compounds have been mimicked with synthetic molecules in
the past decades.[3] There are several strategies to assemble
heterobimetallic coordination compounds,[4] e.g. the metal
atoms can be directly assembled via metal-to-metal bonds,[5]
suitable ligands can force the metals to present in close prox-
imity,[6] and metalloligands can be used.[7] In the latter concept
an organometallic compound such as ferrocene is used as part
of the ligand scaffold.[8] In this context, also [(η6-arene) chro-
mium tricarbonyl] complexes were used to form bimetallic
compounds,[9] mesomorphic materials,[10] polymers,[11] macro-
cycles,[12] and receptors.[13] (η6-Benzoic acid) chromium
tricarbonyl, which was already reported in 1958 by E. O. Fi-
scher,[14] is known to form extended arrays in which the mole-
cules are linked by hydrogen bonds.[15] Surprisingly, the use
of (η6-benzoic acid) chromium tricarbonyl as metalloligand is
limited. In contrast to the coordination chemistry of ferrocenyl-
substituted carboxylic acid[16] the coordination chemistry of
(η6-benzenecarboxylate) chromium tricarbonyl as metalloli-
gand is not well explored. Before we started our investigations
in this area last year,[17] beside [{η6-C6H5COOH}Cr(CO)3]
and [{η6-p-C6H4(COOH)2}Cr(CO)3][15b,18] and some related
group 6 compounds[18b,19] only the group 4 metal benzenecarb-
Results and Discussion
Herein we report on the coordination chemistry of (η6-ben-
zenecarboxylic acid) chromium tricarbonyl as metalloligand
towards zinc and cadmium metal ions in the presence of pyr-
azole ancillary ligands. Reaction of zinc acetate with four dif-
ferent substituted pyrazoles (3,5-dimethyl pyrazole (3,5-Me2-
PzH), 3,5-di-tert-butyl pyrazole (3,5-tBu2PzH), 3,5-diphenyl
pyrazole (3,5-Ph2PzH), and 5-methyl-3-phenyl pyrazole (3-Ph-
* Prof. Dr. P. W. Roesky
Fax: +49-721-608-44854
E-Mail: roesky@kit.edu
[a] Institut für Anorganische Chemie
Karlsruher Institut für Technologie (KIT)
Engesserstraße 15
76128 Karlsruhe, Germany
1818
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 637, 1818–1823

ZnII and CdII Complexes with (η6-Benzenecarboxylate) Cr Tricarbonyl and Pz
5-Me-PzH)) in methanol at room temperature followed by treat- solved in the 13C{1H} NMR spectra of some complexes.
ment with (η6-benzenecarboxylic acid) chromium tricarbonyl af- The 13C{1H} NMR spectra of all compounds show the charac-
forded the desired bimetallic complexes. By applying this pro- teristic signals of the carbonyl groups, which were observed
cedure the zinc-chromium complexes [Zn{(η6-C6H5COO) around 233.3 ppm. The resonances of the carboxylate groups
Cr(CO)3}2(3,5-Me2PzH)2] (1), [Zn{(η6-C6H5COO)Cr(CO)3}2- were observed around 168.7 ppm. In the IR spectra the A1 and
(3,5-tBu2PzH)2]
Ph2PzH)2] (3),
(2),
and
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5- E νCO stretching frequencies were measured at 1963 cm–1,
[Zn{(η6-C6H5COO)Cr(CO)3}2- 1876 cm–1 (1); 1963 cm–1, 1879 cm–1 (2), 1963 cm–1,
(3-Ph-5-Me-PzH)2] (4) were obtained in good yields 1875 cm–1 (3), 1958 cm–1, 1865 cm–1 (4), 1966 cm–1, 1873 cm–1
(Scheme 1). In a similar way the corresponding bimetallic cad- (5) and 1962 cm–1, 1880 cm–1 (6). These findings are in
mium-chromium complexes [Cd{(η6-C6H5COO)Cr(CO)3}2- line with the neutral molecule benzene chromium
(3,5-Me2PzH)2] (5) and [Cd{(η6-C6H5COO)Cr(CO)3}2(3,5- tri-carbonyl (C6H6)Cr(CO)3 (A1: 1980, E: 1910 cm–1).[28]
tBu2PzH)2] (6) were obtained by using cadmium acetate as Only the E vibrations are shifted to lower energy by about
starting material (Scheme 2). All compounds have two (η6-ben- 30 cm–1. Unfortunately, it is not possible to deduce the different
zenecarboxylate) chromium tricarbonyl anions as organometal- coordination modes of the carboxylate groups (1–4: two uni-
lic ligands and two pyrazole ligands in the coordination sphere. dentate modes, 5–6: one chelating bidentate and one unidentate
The variation of substituent on the pyrazole ring did not affect mode of complexation) from the energy differences of the anti-
the nuclearity of the metal complexes under the reaction condi- symmetric and symmetric CO2 vibrations.
tions used. All new compounds were characterized by standard The molecular structures of compounds 1–6 were confirmed
analytical/spectroscopic techniques and the solid-state structures by X-ray crystallography (Figures 1–6). Selected bond lengths
were determined by single-crystal X-ray diffraction.
and angles are given in the captions of corresponding Figures
Compound 1 and 3 crystallize in the monoclinic space group
P21/c, compound 2 and 4 crystallize in the triclinic space group
¯
P1 (Figures 1–4). The molecular structures of complexes 1–4
are similar to each other except the substituent on the pyrazole
ligands. Complexes 1–4 consist of one zinc atom, two pyrazole
ancillary ligands and two organometallic ligands {(η6-
C6H5COO)Cr(CO)3}–. The zinc atom is fourfold coordinated
forming a nearly tetrahedral coordination polyhedron in which
the two carboxylate groups of the {(η6-C6H5COO)Cr(CO)3}–
anion are only κ1-coordinated via the oxygen atoms (O1 and
O6). The coordination sphere is completed by two nitrogen
atoms (N1 and N3) from two different pyrazole ligands. The
average bond angles are around 109.49° (109.47° (1), 109.49°
(2), 109.48° (3), 109.51° (4)), which is close to the bond angle
for an ideal tetrahedron. The Zn–N bond lengths are Zn–N1
2.002(3), Zn–N3 1.991(3) Å (1), Zn–N1 2.026(2), Zn–N3
2.018(2) Å (2), Zn–N1 2.047(7), Zn–N3 2.015(8) Å (3), and
Zn–N1 2.002(4), Zn–N3 2.000(3) Å (4). The Zn–O bond
lengths are Zn–O1 1.943(2), Zn–O6 1.933(2) Å (1) Zn–O1
1.959(2), Zn–O6 1.953(2) Å (2), Zn–O1 1.951(6), Zn–O6
1.936(6) Å (3), and Zn–O1 1.956(3), Zn–O6 1.943 (3) Å (4).
The {(η6-C6H5COO)Cr(CO)3}– anion shows a monodentate
anionic coordination behavior towards the zinc atom. Our ob-
served bonding distances are in good agreement with the data
obtained for other zinc carboxylate complexes containing pyr-
azole ligands, e.g. {[Zn(OAc)2(Hpz)2]·CH3COOH} (Hpz =
pyrazole).[27b] Since the pyrazole NH protons were not depro-
tonated these molecules act as monodentate neutral ligands
towards the zinc atom. For compound 1 these protons could
be localized in the difference Fourier map and were freely re-
fined. The hydrogen atoms of the pyrazole rings are involved
in intramolecular hydrogen bonding with the uncoordinated
oxygen atoms of the carboxylate groups. This interaction is
shown as dashed lines in Figures 1–4.
Scheme 1.
Scheme 2.
1
The H NMR spectra of compounds 1–6 show the expected
set of signals. The characteristic three signals for the benzene
carboxylate unit were observed for all compounds in the range
of 6.30, 5.88, and 5.68 ppm (6.29, 5.89, 5.68 ppm (1); 6.24,
5.85, 5.67 ppm (2); 6.65, 5.86, 5.68 ppm (3); 6.24, 5.86,
5.67 ppm (4); 6.30, 5.88, 5.66 ppm (5); and 6.29, 5.88,
5.65 ppm (6)). The N–H pyrazole signals were usually ob-
served as broad signals in the region between 12 and 13 ppm
(12.61 ppm (1), 12.07 ppm (2), 13.37 ppm (3), 12.75 ppm (4),
12.18 ppm (5), and 11.98 ppm (6)). This clearly indicates that
only the carboxylic acid but not the pyrazole N–H function was
deprotonated during the course of reaction. The signals for the
The observed fourfold coordination of the zinc atom is in
pyrazole substituents are seen in the expected range. The asym- contrast to many other zinc carboxylates containing pyrazole
metric coordination of the pyrazole ligands can be partly re- ligands. Thus, by using 5-phenyl pyrazole-3-carboxylic acid
Z. Anorg. Allg. Chem. 2011, 1818–1823
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1819

B. Murugesapandian, P. W. Roesky
ARTICLE
Figure 1. Solid-state structure of 1 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Zn–N1 2.002(3); Zn–N3 1.991(3); Zn–O1 1.943(2); Zn–O6 1.933(2);
O6–Zn–O1 105.21(11); O6–Zn–N3 109.42(11); O1–Zn–N3
118.09(10); O6–Zn–N1 112.79(10); O1–Zn–N1 103.07(10); N3–Zn–
N1 108.25(11).
Figure 4. Solid-state structure of 4 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Zn–N1 2.002(4), Zn–N3 2.000(3), Zn–O1 1.956(3), Zn–O6 1.943(3);
O6–Zn–O1 108.47(12), O6–Zn–N3 114.16(12), O1–Zn–N3
103.45(13), O6–Zn–N1 102.00(14), O1–Zn–N1 113.76(13), N3–Zn–
N1 115.19(14).
pounds 1–4 was observed in [Zn(CH3COO)2(3-amino-5-
phenyl pyrazole)2].[27a]
Compound 5 and 6 crystallize in the triclinic space group
¯
P1 (Figures 5 and 6). Selected bond lengths and angles are
given in the captions of Figures 5 and 6. The molecular struc-
tures of complexes 5 and 6 are similar to each other. In both
complexes the cadmium atom is fivefold coordinated forming
a strongly distorted square-pyramidal coordination polyhedron.
The coordination polyhedron is made up by three oxygen
atoms O1, O2 and O6 of two {(η6-C6H5COO)Cr(CO)3}–
anions and two nitrogen atoms (N1 and N3) from two different
3,5-dimethyl pyrazole or 3,5-di-tert-butylpyrazole ligands.
Interestingly, the {(η6-C6H5COO)Cr(CO)3}– anions display
two different coordination modes (κ1 and κ2) resulting in
pentacoordinate cadmium atoms in both complexes 5 and 6.
This is contrast to complexes 1–4, which have only fourfold
coordinated zinc metal atoms. The Cd–N bond lengths are Cd–
N1 2.237(2), Cd–N3 2.223(2) Å (5) and Cd–N1 2.291(3), Cd–
N3 2.277(3) Å (6). The Cd–O bond lengths are Cd–O1
2.296(2), Cd–O2 2.474(2) and Cd–O6 2.221(2) (Å) (5), and
Cd–O1 2.325(3), Cd–O2 2.464(3) and Cd–O6 2.258(3) Å. In
both compounds the Cd–O4 bond length is significantly longer
than the Cd–O1 and Cd–O6 bond lengths, which indicates an
asymmetric coordination of the {(η6-C6H5COO)Cr(CO)3}–
anion. The pyrazole NH protons are not deprotonated and thus
these molecules act as monodentate neutral ligand towards the
cadmium atom. The hydrogen atoms of the pyrazole rings are
involved in intramolecular hydrogen bonding with the oxygen
atoms of the carboxylate groups. This interaction is shown as
dashed lines in Figures 5 and 6. Reactions of cadmium acetate
with pyrazoles were reported by Pettinari et al.[27c] The ob-
Figure 2. Solid-state structure of 2 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Zn–N1 2.026(2), Zn–N3 2.018(2), Zn–O1 1.959(2), Zn–O6 1.953(2);
O6–Zn–O1 99.38(8), O6–Zn–N3 104.77(8), O1–Zn–N3 117.34(8),
O6–Zn–N1 118.51(8), O1–Zn–N1 106.67(9), N3–Zn–N1 110.29(9).
Figure 3. Solid-state structure of 3 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Zn–N1 2.047(7), Zn–N3 2.015(8), Zn–O1 1.951(6), Zn–O6 1.936(6),
O6–Zn–O1 107.2(2), O6–Zn–N3 109.5(3), O1–Zn–N3 111.7(3), O6–
Zn–N1 116.4(3), O1–Zn–N1 106.2(3), N3–Zn–N1 105.9(3).
and 3-phenyl pyrazole-4-carboxylic acid 2D and 3D structures tained structural motives are different from compounds 5 and
were obtained, in which the zinc atom is four- and fivefold 6, e.g. [{Cd(μ-OAc)2(3,5-Me2PzH)2}n] contains hexacoordi-
coordinated.[25b] On the other hand a similar structure to com- nate cadmium ions, bridged by exo-bidentate acetate groups.
1820
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 1818–1823

ZnII and CdII Complexes with (η6-Benzenecarboxylate) Cr Tricarbonyl and Pz
Experimental Section
General: Deuterated solvents were obtained from Carl Roth GmbH +
Co. KG (99 at-% D). NMR spectra were recorded with a Bruker Av-
ance II 300 MHz NMR spectrometer. Chemical shifts are referenced
to internal solvent resonances and are reported relative to tetramethyl-
silane. IR spectra were obtained with a Bruker FTIR Tensor 37 via
the Attenuated Total Reflection method (ATR). UV/Vis spectra were
recorded with aVarian Cary 50 spectrometer. Elemental analyses were
carried out with an Elementar Vario EL. The solvents were used as
purchased from commercial sources without further purification. [{η6-
C6H5COOH}Cr(CO)3] was prepared according to literature pro-
cedures.[15b,18a]
Figure 5. Solid-state structure of 5 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Cd–N1 2.237(2), Cd–N3 2.223(2), Cd–O1 2.296(2), Cd–O2 2.474(2),
Cd–O6 2.221(2); O6–Cd–N3 115.19(8), O6–Cd–N1 109.89(8), N3–
Cd–N1 108.36(7), O6–Cd–O1 106.56(7), N3–Cd–O1 119.19(7), N1–
Cd–O1 95.81(7), O6–Cd–O2 92.82(7), N3–Cd–O2 80.09(7), N1–Cd–
O2 147.92(7), O1–Cd–O2 54.99(6).
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5-Me2PzH)2] (1): Zinc acetate
Zn(CH3COO)2·(H2O)2 (44 mg, 0.200 mmol) and 3,5-dimethyl pyr-
azole (39 mg, 0.400 mmol) were dissolved in methanol (10 mL) and
the subsequent mixture was stirred for 1 hour. To this solution [{η6-
C6H5COOH}Cr(CO)3] (101 mg, 0.400 mmol) was added and the re-
sulting mixture was stirred for 6 hours. While stirring a yellow colored
precipitate was formed. Dichloromethane was added to dissolve the
precipitate. Crystals were obtained from this dichloromethane and
methanol mixture. Yield: 120 mg. (78% based on Zn).
C30H26Cr2N4O10Zn: C, 46.68; H, 3.39; N, 7.26. Found: C, 46.87; H,
3.51, N,7.25. UV/Vis (CH2Cl2) [λmax /nm, (ε /L·mol–1·cm–1)] 270 (26
116) (sh), 330 (3980), 408 (854). 1H NMR (DMSO D6, 300 MHz,
25 °C): δ = 12.61 (2 H, br, N–H), 6.29 (d, 4 H, J = 6 Hz, Ar), 5.89 (t,
2 H, J = 6 Hz Ar), 5.82 (s, 2 H, C–H), 5.68 (t, 4 H, J = 6 Hz Ar), 2.15
(s, 12 H, CH3). 13C{1H} NMR (DMSO D6, 75 MHz, 25 °C): δ = 233.2,
168.4, 129.5, 128.20 103.8, 99.6, 97.3, 97.0, 92.9, 12.4, 11.8. IR: ν =
1963 (s), 1876 (s), 1607 (s), 1562 (s), 1500 (s), 1411 (s), 1368 (s),
1295 (s), 1195 (s), 1147 (s), 1051 (s), 1014 (s), 823 (sh), 787 (sh), 747
(s), 722 (s), 681 (s), 623 (s), 579 (s), 532(s) cm–1.
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5-tBu2PzH)2] (2): Zinc acetate
Zn(CH3COO)2·(H2O)2 (44 mg, 0.200 mmol) and 3,5-di-tert-butyl pyr-
azole (0.72 mg, 0.400 mmol) were dissolved in methanol (20 mL) and
the subsequent mixture was stirred for 1 hour. To this solution [η6-
C6H5COOH}Cr(CO)3] (101 mg, 0.400 mmol) was added and the re-
sulting mixture was stirred for 6 hours. While stirring a yellow colored
precipitate was formed. Dichloromethane was added to dissolve the
precipitate. Crystals were obtained from this dichloromethane and
methanol mixture. Yield: 140 mg. (74% based on Zn). Calcd for
C42H50Cr2N4O10Zn: C, 53.65; H, 5.36; N, 5.96. Found: C, 53.04; H,
5.52; N, 5.89. UV/Vis (CH2Cl2) [λmax /nm, (ε /L·mol–1·cm–1)] 270 (16
484) (sh), 330 (2734), 406 (534). 1H NMR (DMSO D6, 300 MHz,
25 °C): δ = 12.07 (s, 2 H, NH), 6.24 (d, 4 H, J = 3 Hz, Ar), 5.85
(t, 2 H, J = 6 Hz, Ar), 5.83 (s, 2 H, CH), 5.67 (t, 4 H, J = 6 Hz, Ar),
1.22 (s, 36 H, CH3). 13C{1H} NMR (DMSO D6, 75 MHz, 25 °C): δ =
233.2, 168.8, 129.6, 127.9, 98.7, 97.2, 96.9, 96.6, 93.0, 31.1, 30.5. IR:
ν = 1963 (s), 1905 (sh), 1879 (s), 1605 (sh), 1566 (s), 1520 (sh), 1497
(s), 1463 (s), 1410 (s), 1369 (s), 1294 (s), 1250 (s), 1204 (s), 1144 (s),
1025 (s), 996 (s), 930 (s), 878 (s), 783 (sh), 723 (s), 681 (s), 651 (s),
621 (s), 572 (sh), 526 (s) cm–1.
Figure 6. Solid-state structure of 6 showing the atom labeling scheme
omitting hydrogen atoms expect the pyrazole N–H atoms. Hydrogen
bonds are shown as dashed lines. Selected bond lengths /Å or angles /°:
Cd–N1 2.291(3), Cd–N3 2.277(3), Cd–O1 2.325(3), Cd–O2 2.464(3),
Cd–O6 2.258(3); O6–Cd–N3 126.22(12), O6–Cd–N1 90.38(13), N3–
Cd–N1 108.76(12), O6–Cd–O1 107.61(12), N3–Cd–O1 93.81(11),
N1–Cd–O1 134.57(11), O6–Cd–O2 112.47(12), N3–Cd–O2
119.92(11), N1–Cd–O2 80.37(11), O1–Cd–O2 54.26(11).
Conlusions
We have prepared new six bimetallic zinc-chromium or cad-
mium-chromium complexes by using the organometallic li-
gand {η6-C6H5COO}Cr(CO)3. The complexes were obtained
by reaction of zinc and cadmium acetates with {η6-
C6H5COOH}Cr(CO)3 in the presence of pyrazole ancillary li-
gands. Independent of the nature of the substituents of the pyr-
azole ligand only bimetallic but no polymeric compounds were
formed. The pyrazole rings, which were not deprotonated dur-
ing the course of reaction, act as neutral monodentate ligands
in all complexes. In contrast, the {(η6-C6H5COO)Cr(CO)3}–
anion coordinates as anionic monodentate ligand in the zinc
complexes while it acts as anionic monodentate and bidentate
ligand in the cadmium complexes.
[Zn{(η6-C6H5COO)Cr(CO)3}2(3,5-Ph2PzH)2] (3): Zinc acetate
Zn(CH3COO)2·(H2O)2 (44 mg, 0.200 mmol) and 3,5-di-phenyl pyr-
azole (88 mg, 0.400 mmol) were dissolved in methanol (20 mL) and
the subsequent mixture was stirred for 1 hour. To this solution [{η6-
C6H5COOH}Cr(CO)3] (101 mg, 0.400 mmol) was added and the re-
sulting mixture was stirred for 6 hours. While stirring a yellow colored
precipitate was formed. Dichloromethane was added to dissolve the
precipitate. Crystals were obtained from this dichloromethane and
methanol mixture. Yield: 145 mg. (76% based on Zn).
Z. Anorg. Allg. Chem. 2011, 1818–1823
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1821

B. Murugesapandian, P. W. Roesky
ARTICLE
C50H34Cr2N4O10Zn·(0.25H2O): C, 58.61; H, 3.39; N, 5.47. Found: C,
Ar), 5.88 (t, 2 H, J = 6 Hz, Ar), 5.82 (s, 2 H, C–H), 5.65
57.99; H, 3.41; N, 5.43. UV/Vis (CH2Cl2) [λmax /nm, (ε /L·mol–1·cm– (t , 4 H, J = 6 Hz, Ar), 1.22 (s, 36 H, CH3). 13C{1H} NMR (DMSO
1
1)] 270 (56 394) (sh), 330 (2048), 403 (511). H NMR (DMSO D6,
D6, 75 MHz, 25 °C): δ = 233.4, 169.0, 129.6, 127.9, 99.5, 97.8, 97.2,
96.4, 92.7, 31.0, 30.5. IR: ν = 1962 (s), 1880 (s), 1554 (s), 1494 (s),
300 MHz, 25 °C): δ = 13.37 (s, 2 H, NH), 7.84 (8 H, b, Ar), 7.45
(8 H, b, Ar), 7.34 (4 H, b, Ar), 7.18 (s, 2 H, CH), 6.65 (d, 4 H, J = 1456 (sh), 1386 (s), 1283 (s), 1249 (s), 1199 (s), 1139 (s), 1047 (s),
6 Hz, Ar), 5.86 (t, 2 H, J = 6 Hz, Ar), 5.68 (t, 4 H, J = 6 Hz, Ar). 1008 (s), 935 (sh), 846 (s), 806 (s), 720 (s), 683 (s), 652 (s), 619 (s),
13C{1H} NMR (DMSO D6, 75 MHz, 25 °C): δ = 233.3, 168.7, 151.3, 525 (s) cm–1.
143.4, 133.7, 129.0, 128.7, 128.1, 127.5, 125.1, 99.6, 98.8, 97.2, 96.9,
93.1. IR: ν = 1963 (s), 1875(s), 1595 (s), 1556 (s), 1494 (sh), 1453
X-ray Crystallographic Studies of 1–6.
(s), 1411 (s), 1367 (s), 1295 (sh), 1272 (s), 1200 (s), 1150 (s), 1106
(s), 1076 (sh), 1059 (s), 1026 (sh), 1006 (s), 980 (s), 953 (s), 919 (s),
821 (s), 762 (s), 685 (s), 657 (s), 620 (s), 569 (sh), 529 (s) cm–1.
Crystals of 1–4 were obtained from a dichloromethane/methanol mix-
ture, crystals of 5 from ethanol, and crystals of 6 were obtained from
methanol. A suitable crystal was covered in mineral oil (Aldrich) and
mounted onto a glass fiber. The crystal was transferred directly to the
200 K or 150 K cold N2 stream of a Stoe IPDS 2.
[Zn{(η6-C6H5COO)Cr(CO)3}2(3-Ph-5-Me-PzH)2] (4): Zinc acetate
Zn(CH3COO)2·(H2O)2 (44 mg, 0.200 mmol) and 5-methyl-3-phenyl
pyrazole (63 mg, 0.400 mmol) were dissolved in methanol (20 mL)
and the subsequent mixture was stirred for 1 hour. To this solution
[{η6-C6H5COOH}Cr(CO)3] (101 mg, 0.400 mmol) was added and the
resulting mixture was stirred for 6 hours. While stirring a yellow col-
ored precipitate was formed. Dichloromethane was added to dissolve
the precipitate. Crystals were obtained from this dichloromethane and
methanol mixture. Yield: 135 mg. (75% based on Zn).
C40H30Cr2N4O10Zn: C, 53.62; H, 3.37; N, 6.25. Found: C, 53.77; H,
3.69; N, 6.72. UV/Vis (CH2Cl2) [λmax /nm, (ε /L·mol–1·cm–1)] 270
(51599) (sh), 330 (16341), 404 (3900). 1H NMR (DMSO D6,
300 MHz, 25 °C): δ = 12.75 (s, 2 H, NH), 7.74 (4 H, b, Ar), 7.39
(4 H, b, Ar), 7.27 (2 H, b, Ar), 6.44 (s, 2 H, CH), 6.24 (4 H, b, Ar),
5.86 (2 H, b, Ar), 5.67 (4 H, b, Ar), 2.25 (s, 6 H, CH3). 13C{1H} NMR
(DMSO D6, 75 MHz, 25 °C): δ = 233.3, 168.7, 131.1, 129.6, 128.7,
127.9, 127.4, 125.0, 101.4, 98.7, 97.3, 96.9, 93.0, 11.3. IR: ν = 1958
(s), 1904 (sh), 1865 (s), 1601 (s), 1558 (s), 1497 (s), 1367 (s), 1300
(s), 1276 (s), 1217 (s), 1181 (s), 1149 (s), 1076 (sh), 1049 (s), 1009
(s), 953 (s), 911 (s), 820 (s), 772 (sh), 761 (sh), 721 (s), 679 (sh), 659
Solution and refinement: SHELXS-97 [29], SHELXL-97
.
[29]
Crystal data for 1: C30H26Cr2N4O10Zn, M = 771.92, monoclinic, a =
11.615(2) Å, b = 10.421(2) Å, c = 27.024(5) Å, β = 101.09(3)°, V =
3210.1(11) Å3, T = 200(2) K, space group P21/c, Z = 4, μ(Mo-Kα) =
1.468 mm–1, 32727 reflections measured, 8632 independent reflections
(Rint = 0.0838). The final R1 values were 0.0490 [I Ͼ 2σ(I)). The final
wR(F2) values were 0.1163 (all data). The goodness of fit on F2 was
1.013.
Crystal data for 2: C42H50Cr2N4O10Zn, M = 940.23, triclinic, a =
12.784(3) Å, b = 13.539(3) Å, c = 14.154(3) Å, α = 69.75(3)°, β =
79.42(3)°, γ = 75.77(3)°, V = 2214.9(8) Å3, T = 150(2) K, space group
–1
¯
P1, Z = 2, μ(Mo-Kα) = 1.078 mm , 22139 reflections measured, 9374
independent reflections (Rint = 0.0699). The final R1 values were
0.0434 [I Ͼ 2σ(I)). The final wR(F2) values were 0.1218 (all data).
The goodness of fit on F2 was 0.985.
(s), 625 (s), 576 (sh), 531 (s) cm–1
.
[Cd{(η6-C6H5COO)Cr(CO)3}2(3,5-Me2PzH)2] (5): [{η6-C6H5CO-
OH}Cr(CO)3] (101 mg, 0.400 mmol) was dissolved in ethanol
(10 mL). To this solution cadmium acetate (Cd(CH3COO)2·2H2O)
(54 mg, 0.200 mmol) was added and the subsequent mixture was
stirred for 1 hour. 3,5-Dimethyl pyrazole (39 mg, 0.400 mmol) was
added to the above solution and the resulting mixture was afterwards
stirred for 6 hours. The solution filtered and kept for crystallization.
Yield: 125 mg. (77% based on Cd). C30H26CdCr2N4O10: C, 44.00; H,
3.20; N, 6.84. Found: C, 43.71; H, 3.23; N, 6.56. UV/Vis (CH2Cl2)
[λmax /nm, (ε /L·mol–1·cm–1)] 266 (32 657) (sh), 330 (12 268), 404
Crystal data for 3: C50H34Cr2N4O10Zn·(0.25H2O), M = 1024.69, mo-
noclinic, a = 11.682(2) Å, b = 17.433(4) Å, c = 22.521(5) Å, β =
97.30(3)°, V = 4549.3(16) Å3, T = 150(2) K, space group P21/c, Z =
4, μ(Mo-Kα) = 1.058 mm–1, 16750 reflections measured, 9381 inde-
pendent reflections (Rint = 0.1996). The final R1 values were 0.0757 [I
Ͼ 2σ(I)). The final wR(F2) values were 0.1873 (all data). The goodness
of fit on F2 was 0.725.
Crystal data for 4: C40H30Cr2N4O10Zn, M = 896.05, triclinic, a =
11.855(2) Å, b = 13.777(3) Å, c = 13.893(3) Å, α = 97.67(3)°, β =
104.91(3)°, γ = 115.13(3)°, V = 1907.1(7) Å3, T = 150(2) K, space
1
(2519). H NMR (DMSO D6, 300 MHz, 25 °C): δ = 12.18 (2 H, br,
–1
¯
N–H), 6.30 (d, 4 H, J = 6 Hz, Ar), 5.88 (t, 2 H, J = 6 Hz, Ar), 5.76
(2 H, C–H), 5.66 (t, 4 H, J = 6 Hz, Ar), 2.13 (s, 6 H, CH3). 13C{1H}
NMR (DMSO D6, 75 MHz, 25 °C): δ = 233.4, 169.1, 129.7, 127.9,
103.4, 99.5, 97.8, 97.2, 92.7, 11.9. IR: ν = 1966 (s), 1873(s), 1578 (s),
1494 (s) 1377 (s), 1300 (s), 1169 (s), 1031 (s), 880 (sh), 816 (s), 719
(s), 657 (s), 624 (s), 532 (s) cm–1.
group P1, Z = 2, μ(Mo-Kα) = 1.248 mm , 17441 reflections measured,
8046 independent reflections (Rint = 0.1112). The final R1 values were
0.0580 [I Ͼ 2σ(I)). The final wR(F2) values were 0.1473 (all data).
The goodness of fit on F2 was 0.920.
Crystal data for 5: C30H26CdCr2N4O10, M = 818.95, triclinic, a =
10.229(2) Å, b = 10.363(2) Å, c = 15.957(3) Å, α = 90.59(3)°, β =
[Cd{(η6-C6H5COO)Cr(CO)3}2(3,5-tBu2PzH)2] (6): Cadmium acetate
(Cd(CH3COO)2·(H2O)2 (54 mg, 0.200 mmol) and 3,5-di-tert-butyl
pyrazole (72 mg, 0.400 mmol) were dissolved in methanol (10 mL)
and the subsequent mixture was stirred for 1 hour. To this solution
[{η6-C6H5COOH}Cr(CO)3] (101 mg, 0.400 mmol) was added and the
resulting mixture was afterwards stirred for 6 hours. The solution fil-
93.50(3)°, γ = 105.13(3)°, V = 1629.1(6) Å3, T = 200(2) K, space group
–1
¯
P1, Z = 2, μ(Mo-Kα) = 1.363 mm , 12296 reflections measured, 5864
independent reflections (Rint = 0.0542). The final R1 values were
0.0283 [I Ͼ 2σ(I)). The final wR(F2) values were 0.0783 (all data).
The goodness of fit on F2 was 1.016.
tered and kept for crystallization. Yield: 140 mg. (69% based on Cd). Crystal data for 6: C42H50CdCr2N4O10·(0.25 CH3OH), M = 995.27,
C42H50CdCr2N4O10·(0.25 CH3OH): C, 50.99; H, 5.16; N, 5.63. Found:
triclinic, a = 13.288(3) Å, b = 13.733(3) Å, c = 15.107(3) Å, α =
C, 51.08; H, 5.29; N, 5.79. UV/Vis (CH2Cl2) [λmax /nm, (ε /L·mol–
66.14(3)°, β = 70.23(3)°, γ = 73.55(3)°, V = 2338.1(8) Å3, T = 200(2)
1
–1
1·cm–1)] 268 (28 094) (sh), 329 (4243), 402 (639). H NMR (DMSO K, space group P1, Z = 2, μ(Mo-Kα) = 0.964 mm , 20931 reflections
¯
D6, 300 MHz, 25 °C): δ = 11.98 (s, 2 H, NH), 6.29 (d, 4 H, J = 6 Hz, measured, 9788 independent reflections (Rint = 0.0515). The final R1
1822
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 1818–1823

ZnII and CdII Complexes with (η6-Benzenecarboxylate) Cr Tricarbonyl and Pz
values were 0.0448 [I Ͼ 2σ(I)). The final wR(F2) values were 0.1215
(all data). The goodness of fit on F2 was 0.932.
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Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge Crystal-
lographic Data Centre as a supplementary publication no. CCDC-
829753, -829754, -829755, -829756, -829757, -829758. Copies of the
data can be obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB21EZ, UK (Fax: +44-1223-336-033; E-mail:
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Acknowledgement
This work was supported by the Alexander-von-Humboldt Stiftung
(Fellowship for B.M.), by the Deutsche Forschungsgemeinschaft
(DFG)-funded transregional collaborative research center SFB/TRR 88
“Cooperative effects in homo- and hetero-metalic complexes (3MET)”,
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Received: June 16, 2011
Published Online: September 26, 2011
Z. Anorg. Allg. Chem. 2011, 1818–1823
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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