N-heterocyclic carbene stabilized dichlorosilylene transition-metal complexes of V(I), Co(I), and Fe(0)

Article abstract of DOI:10.1021/ic201096c

Reactions of N-heterocyclic carbene stabilized dichlorosilylene IPr·SiCl₂ (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2- ylidene) with (η⁵-C₅H₅)V(CO)₄, (η⁵-C₅H₅)Co(CO)₂, and Fe ₂(CO)₉ afford dichlorosilylene complexes IPr·SiCl₂·V(CO)₃(η⁵-C ₅H₅) (2), IPr·SiCl₂·Co(CO)( η⁵-C₅H₅) (3), and IPr·SiCl ₂·Fe(CO)₄ (4), respectively. Complexes 2-4 are stable under an inert atmosphere, are soluble in common organic solvents, and have been characterized by elemental analysis and multinuclear (¹H, ¹³C, and ²⁹Si) NMR spectroscopy. Molecular structures of 2-4 have been determined by single crystal X-ray crystallographic studies and refined with nonspherical scattering factors.

Full text of DOI:10.1021/ic201096c

ARTICLE
pubs.acs.org/IC
N-Heterocyclic Carbene Stabilized Dichlorosilylene Transition-Metal
Complexes of V(I), Co(I), and Fe(0)
Rajendra S. Ghadwal,* Ramachandran Azhakar, Kevin Pr€opper, Julian J. Holstein, Birger Dittrich,* and
Herbert W. Roesky*
Institut f€ur Anorganische Chemie der Universit€at G€ottingen, Tammannstrasse 4, D 37077 G€ottingen, Germany
S Supporting Information
b
ABSTRACT: Reactions of N-heterocyclic carbene stabilized
dichlorosilylene IPr SiCl2 (1) (IPr = 1,3-bis(2,6-diisopropyl-
3
phenyl)imidazol-2-ylidene) with (η5-C5H5)V(CO)4, (η5-
C5H5)Co(CO)2, and Fe2(CO)9 afford dichlorosilylene com-
plexes IPr SiCl2 V(CO)3(η5-C5H5) (2), IPr SiCl2 Co(CO)-
3
3
3
3
(η5-C5H5) (3), and IPr SiCl2 Fe(CO)4 (4), respectively.
3
3
Complexes 2ꢀ4 are stable under an inert atmosphere, are
soluble in common organic solvents, and have been character-
ized by elemental analysis and multinuclear (1H, 13C, and 29Si)
NMR spectroscopy. Molecular structures of 2ꢀ4 have been determined by single crystal X-ray crystallographic studies and refined
with nonspherical scattering factors.
’ INTRODUCTION
molecular orbital (HOMO) and an empty p-orbital as the lowest
unoccupied molecular orbital (LUMO) in the singlet ground
(1A) state. Therefore, silylenes can in principle behave as Lewis
acids as well as Lewis bases and are known to possess an
ambiphilic nature.23 Very recently, we isolated the first Lewis-
N-heterocyclic carbenes (NHCs) have proven highly versatile
σ-donor ligands for transition-metal (TM) complexes1,2 and as
effective Lewis bases to stabilize reactive main group element
species3,4 and as organocatalysts on their own right.5 Use of
NHCs as spectator ligands, particularly as alternatives to phos-
phines (R3P), resulted in a second generation of Grubbs
catalysts.6 This is one of the remarkable developments in
organometallic chemistry. Similarly, chemistry of TMꢀsilylene
complexes has attracted considerable attention7 during the last
two decades. TMꢀsilylene complexes have been proposed as
intermediates in catalytic hydrosilylation,8 dehydrosilylation of
organosilicon compounds,9 redistribution of substituents on
organosilicon compounds,10 and deoligomerization of disilanyl-
metal complexes to monosilyl derivatives.11 In general, silylenes
are compounds with a neutral divalent silicon atom, and there-
fore, they are highly reactive species to be isolated at normal
laboratory conditions.12 Coordination to a TM center offers a
convenient synthetic approach to trap or to generate such highly
reactive species.13 Remarkable contributions to this field have
been made by Tilley and others.7,14 Availability of the first stable
N-heterocyclic silylene (NHSi)15 and its application as a ligand
for TM complexes introduced a direct method to prepare
TMꢀsilylene complexes.16ꢀ20 Among acyclic silylenes, dichlor-
osilylene (SiCl2) is one of the extremely reactive species and has
academic and industrial importance. SiCl2 readily polymerizes to
(SiCl2)n or decomposes to Si and SiCl4.21 Therefore access to
TM complexes containing SiCl2 as a ligand is rare and based on
indirect multistep methods.22 Moreover, these reactions often
lead to a mixture of several products. In general, silylenes (e.g.,
SiX2, X = halogen, H, alkyl, or aryl) are divalent neutral silicon
species with the lone pair of electrons as the highest occupied
base stabilized dichlorosilylene4 IPr SiCl2 (1) (IPr = 1,3-bis(2,6-
3
diisopropylphenyl)imidazol-2-ylidene) in very good yield by
reductive dehydrochlorination of HSiCl3 using NHC. This
method was the basis for developing silylene chemistry on a
broader scale, without using alkali metals for the reduction.
However even more important was the increase in the yield of
silylene. Compound 1 consists of a three coordinate silicon atom
containing a stereoactive lone pair of electrons. Therefore, 1
should serve as a convenient and readily available source of a
neutral σ-donor ligand for TM complexes. In 1, NHC is a Lewis
base, and SiCl2 behaves as a Lewis acid. Ambiphilic nature of
SiCl2, in which it behaves as a Lewis acid as well as a Lewis base at
the same time, has been already demonstrated in our previous
reports.19,20,23 We have investigated the properties of 1 as a Lewis
base,23 and its oxidative addition to organic substrates,24 func-
tionalization of NHC,25 and use of 1 as a σ-donor ligand for the
TM complexes [Co(CO)3{SiCl2(IPr)}2][CoCl3(THF)] A19
and Ni(CO)2{SiCl2(IPr)}2 B.20 Formation of an ionic (A) and
a neutral (B) bis-silylene complex further convinced us to
continue our studies on the chemistry of TM complexes contain-
ing 1 as a ligand. A survey of literature reveals that there are only a
few complexes, such as (CO)5VSiH3, (η5-C5H5)2V(SiCl3)2,
(η5-C5H5)V(NtBu)(NHtBu)Si(SiMe3)3, and (η5-C5H5)V(L)-
(SiHRR0) (L = 1,2-bis(dimethylphosphino)ethane; R = Ph or
Received: May 24, 2011
Published: July 22, 2011
r
2011 American Chemical Society
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|

Inorganic Chemistry
ARTICLE
Mes, and R0 = Ph or H), containing vanadiumꢀsilicon bonds
which have been characterized by X-ray crystallographic studies.26
Moreover, to the best of our knowledge no vanadiumꢀsilylene
complex has been isolated so far. The lack of progress in this area
is due to the paramagnetic properties of most vanadium
complexes.26 Therefore, we became interested in exploring the
chemistry of TM, especially vanadium, complexes using 1 as a
ligand. Ligand substitution reactions are essential for the applica-
tion of TM organometallic compounds as homogeneous cata-
lysts. Compared to the TMꢀcarbene complexes, TMꢀsilylene
complexes derived from stable silylenes are still elusive. Herein,
we report on a convenient access to TMꢀsilylene com-
plexes IPr SiCl2 V(CO)3(η5-C5H5) (2), IPr SiCl2 Co(CO)-
Synthesis of IPr SiCl2 Co(CO)(η5-C5H5) (3). A toluene solu-
3
3
tion of (η5-C5H5)Co(CO)2 (0.25 g, 1.39 mmol) was added to a stirred
solution of IPr SiCl2 (1) (0.67 g, 1.37 mmol) at 0 °C with constant
3
stirring. Stirring of the reaction mixture was continued at room
temperature for 12 h. Volatiles were removed under vacuum to obtain
an orange solid. Recrystallization from a mixture of dichloromethane
(10 mL) and n-hexane (10 mL) solution at ꢀ35 °C afforded complex 4
as orange-yellow crystals (0.51 g, 58%). Anal. calcd for C33H41Cl2Co-
N2OSi (M = 639): C, 61.97; H, 6.46; N, 4.38. Found (%): C, 61.89; H,
6.38; N, 4.27. 1H NMR (200 MHz, CD2Cl2, 298 K): δ 1.32 (d, J = 6.84
Hz, 12H, CHMe2), 1.68 (d, J = 6.66 Hz, 12H, CHMe2), 3.00 (q, J = 6.76
Hz, 4H, CHMe2), 4.49 (s, 5H, C5H5), 7.20 (s, 2H, NCH), 7.36ꢀ7.42
(m, 4H, C6H3), 7.50ꢀ7.56 (m, 2H, C6H3) ppm. 13C{1H} NMR (125
MHz, CD2Cl2, 298 K): δ 22.98 (CHMe2), 26.30 (CHMe2), 29.66
(CHMe2), 82.17 (C5H5), 124.87 (NCH), 125.23, 125.82, 126.11,
129.54, 131.67, 132.48, 134.76 (C6H3), 146.33 (ipso-C6H3), 155.01
(NCN) 205.97 (br, CO) ppm. 29Si NMR (99 MHz, CD2Cl2, 298 K): δ
31.86 ppm.
3
3
3
3
(η5-C5H5) (3), and IPr SiCl2 Fe(CO)4 (4) by ligand substitu-
3
3
tion reaction. Complexes 2ꢀ4 have been characterized by ele-
mental analyses and NMR spectroscopy. Molecular structures of
2ꢀ4 have been established by single crystal X-ray crystallography.
Complex 2 is the first vanadiumꢀsilylene complex which is
structurally characterized by single crystal X-ray crystallography.
The quality of the X-ray structures in terms of accuracy and precision
has been improved by using nonspherical scattering factors.
Synthesis of IPr SiCl2 Fe(CO)4 (4). Toluene (50 mL) was
3
3
added to a mixture of IPr SiCl2 (1) (1.56 g, 3.20 mmol) and Fe2(CO)9
3
(1.16 g, 3.19 mmol) in a Schlenk flask at room temperature. After 12 h of
stirring, all volatiles were removed under vacuum to obtain a brown
solid. Recrystallization from a solution of dichloromethane (15 mL) and
n-hexane (10 mL) at ꢀ35 °C afforded complex 4 as colorless crystals
(1.02 g, 48%). Anal. calcd for C31H36Cl2FeN2O4Si (M = 655): C, 56.80;
H, 5.54; N, 4.27. Found (%): C, 56.71; H, 5.43; N, 4.22. 1H NMR (200
MHz, CD2Cl2, 298 K): δ 1.13 (d, J = 6.70 Hz, 12H, CHMe2), 1.41 (d, J =
6.54 Hz, 12H, CHMe2), 2.72 (m, 4H, CHMe2), 7.15 (s, 2H, NCH),
7.30ꢀ7.51 (m, 6H, C6H3) ppm. 13C{1H} NMR (125 MHz, CD2Cl2,
298 K): δ 22.74 (CHMe2), 26.51 (CHMe2), 29.46 (CHMe2), 125.02
(NCH), 125.51, 127.99, 128.58, 131.15, 134.13 (C6H3), 145.96 (ipso-
C6H3) 214.95 (CO) ppm. 29Si NMR (99 MHz, CD2Cl2, 298 K): δ 59.19
ppm. 1H NMR (500 MHz, C6D6, 298 K): δ 0.92 (d, J = 6.69 Hz, 12H,
CHMe2), 1.44 (d, J = 6.54 Hz, 12H, CHMe2), 2.77 (m, 4H, CHMe2),
6.36 (s, 2H, NCH), 6.99ꢀ7.28 (m, 6H, C6H3) ppm. 13C{1H} NMR
(125 MHz, C6D6, 298 K): δ 22.76 (CHMe2), 26.05 (CHMe2), 29.12
(CHMe2), 124.61 (NCH), 125.63, 126.53, 127.81, 129.65, 130.91,
132.02, 134.15 (C6H3), 146.62 (ipso-C6H3) 191.56, 215.81 (CO) ppm.
29Si NMR (99 MHz, C6D6, 298 K): δ 59.20 ppm.
’ EXPERIMENTAL SECTION
General Procedures. All syntheses and manipulations were
performed under an inert atmosphere of nitrogen using Schlenk line
techniques or a glovebox. The solvents used were purified by MBRAUN
MB SPS-800 solvent purification system. NHC stabilized dichlor-
osilylene IPr SiCl2 (1) was prepared4 according to the method given
3
in the literature. Without further purification, (η5-C5H5)V(CO)4,
(η5-C5H5)Co(CO)2, (abcr GmbH & Co. KG) and Fe2(CO)9
(Aldrich) were used as received. C6D6 (Na/benzophenone ketyl)
and CD2Cl2 (CaH2) were distilled under nitrogen prior to use. 1H, 13C,
29Si, and 51V NMR spectra were recorded using Bruker Avance DPX 200
or Bruker Avance DRX 500 spectrometer. 51V NMR chemical shifts are
reported relative to VOCl3 as an external reference. Elemental analyses
were obtained from the Analytical Laboratory of the Institute of
Inorganic Chemistry at the University of G€ottingen.
Synthesis of IPr SiCl2 V(CO)3(η5-C5H5) (2). To a Schlenk flask
3
3
containing IPr SiCl2 (1) (0.59 g, 1.21 mmol) and (η5-C5H5)V(CO)4
3
’ RESULTS AND DISCUSSION
(0.28 g, 1.22 mmol) was added toluene (40 mL) at room temperature
with constant stirring. The reaction mixture was further stirred for 12 h.
A small amount of insoluble material was removed by filtration. The
volatiles from the red filtrate were removed under vacuum to obtain a
brown solid. The solid was dissolved in toluene (20 mL) and stored
at ꢀ35 °C in a freezer to yield compound IPr SiCl2 V(CO)3(η5-C5H5)
Synthesis and Characterization. Reaction of IPr SiCl2 (1)
3
with (η5-C5H5)V(CO)4, (η5-C5H5)Co(CO)2, and Fe2(CO)9
afforded NHC stabilized dichlorosilylene complexes IPr SiCl2
3
3
V(CO)3(η5-C5H5) (2), IPr SiCl2 Co(CO)(η5-C5H5) (3), and
3
3
3
3
IPr SiCl2 Fe(CO)4 (4), respectively (Scheme 1).
3
3
(2) as red crystals (0.61 g, 73%). Anal. calcd (%) for C35H41Cl2N2O3SiV
(M = 687): C, 61.13; H, 6.01; N, 4.07. Found (%): C, 61.01; H, 5.87; N,
4.09. 1H NMR (200 MHz, C6D6, 298 K): δ 0.94 (d, J = 6.84 Hz, 12H,
CHMe2), 1.56 (d, J = 6.62 Hz, 12H, CHMe2), 2.99 (q, J = 6.70 Hz, 4H,
CHMe2), 4.65 (s, 5H, C5H5), 6.37 (s, 2H, NCH), 6.98ꢀ7.24 (m, 6H,
C6H3) ppm. 13C{1H} NMR (75 MHz, C6D6, 298 K): δ 22.63
(CHMe2), 26.43 (CHMe2), 29.19 (CHMe2), 91.07 (C5H5), 124.77
(NCH), 125.63, 126.39, 129.27, 131.26, 135.13, 137.84 (C6H3), 145.58
(ipso-C6H3) ppm. 1H NMR (200 MHz, CD2Cl2, 298 K): δ 1.10 (d, J =
6.80 Hz, 12H, CHMe2), 1.41 (d, J = 6.62 Hz, 12H, CHMe2), 2.83 (q, J =
6.70 Hz, 4H, CHMe2), 4.57 (s, 5H, C5H5), 7.20 (s, 2H, NCH),
7.36ꢀ7.51 (m, 6H, C6H3) ppm. 13C{1H} NMR (125 MHz, CD2Cl2,
298 K): δ 22.42 (CHMe2), 26.33 (CHMe2), 29.14 (CHMe2), 90.78
(C5H5), 124.70 (NCH), 125.19, 127.00, 128.38, 129.19, 131.11, 134.97,
138.17 (C6H3), 145.58 (ipso-C6H3), 158.10 (NCN), 259.20ꢀ263.03
Complexes 2ꢀ4 are crystalline solids, soluble in common
organic solvents, and stable under an inert atmosphere. These
complexes were characterized by elemental analyses and 1H, 13C,
and 29Si NMR spectroscopic studies. 1H NMR spectra of 2ꢀ4
show two sets of resonances for methyl protons (CHMe2) of
isopropyl groups, whereas methine protons appear as a multiplet.
Imidazole backbone protons exhibit a singlet and show solvent
dependence. Complexes 2 and 3 each show a singlet for
cyclopentadienyl (C5H5) protons. 13C{1H} NMR spectra of
2ꢀ4 exhibit usual resonances for the IPr ligand. In the 13C NMR
spectra (in CD2Cl2) of 2 and 3, a resonance at δ 90.78 and
82.17 ppm, respectively, may be assigned for each cyclopenta-
dienyl group. Complex 2 exhibits a broad 29Si NMR signal at δ
88.70 ppm due to the presence of paramagnetic vanadium.
Similar broadening can also be seen in the 13C{1H} NMR
spectrum of 2 for carbonyl groups (δ 259.20ꢀ263.03 ppm).
(br, CO) ppm. 29Si NMR (99 MHz, CD2Cl2, 298 K): δ 88.70 ppm. 51
NMR (78 MHz, CD2Cl2, 298 K): δ ꢀ1593.46 ppm.
V
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Inorganic Chemistry
ARTICLE
Scheme 1
However, resonances for the IPr ligand in 2 exhibit without any
broadening. 51V NMR resonance for 2 appears at δ ꢀ1593.46
ppm, which is consistent with those observed for analogues
vanadium complexes.26 For the carbonyl group, 3 and 4 show
13C NMR resonances between δ 191 and 219 ppm. 29Si NMR
spectra of 3 and 4 exhibit a resonance at 31.86 and 59.20 ppm,
which is consistent with those observed for TMꢀsilylene
complexes.19,20
Single Crystal X-ray Structure Determination. Single Crys-
tal X-ray Structures. Molecular structures of compounds 2ꢀ4
were established by single-crystal X-ray crystallographic studies
and corresponding ORTEP-representations are shown in
Figures 1ꢀ3. Crystallographic data for 2ꢀ4 are summarized in
Table 1. All crystals were measured on a Bruker three-circle
diffractometer equipped with a SMART 6000 CCD area detector
and a CuKR rotation anode. Integrations were performed with
SAINT.27 Intensity data for all compounds were corrected for
absorption and scaled with SADABS.28 Structures were solved by
direct methods and initially refined by full-matrix least-squares
methods on F2 with the program SHELXL-97,29 utilizing anisotropic
displacement parameters for nonhydrogen atoms. The structural
model was improved by a subsequent refinement with nonspherical
scattering factors,30 which was initiated by converged IAM parameter
values. The scattering-factor model used in this refinement was based
on the Hansen and Coppens multipole formalism.31 For com-
pounds 2 and 4 hydrogen atoms were included in the model by
constraints via a riding model,and in case of 3, hydrogen atoms
were refined freely. Instead of adjusting the respective multipole
parameters to the experimental data, which requires Bragg data
to a high resolution, multipole parameters were predicted from
theoretical calculations on each whole molecule, using the
density functional theory (DFT) functional B3LYP and 6-31
g* as the basis set. This procedure is different to the fragment-
based invariom approach.32 Prior to refinement with XDLSM as
part of the XD suite,33 input files were processed with the
program InvariomTool.32 The criterion for observed reflections
was [I > 3σ (I)]. Only positional and displacement parameters of
nonhydrogen atoms were adjusted in the nonspherical atom
refinement, so that the number of parameters was not increased
in comparison to the IAM. Bond distances to hydrogen atoms
were set to values from geometry optimization.34 These asphe-
rical atom refinements share the benefits of a conventional charge
density refinement. For all compounds, parameter precision (as
indicated by parameter standard deviations) and figures of merit
improve. Anisotropic displacement parameters (ADPs) become
deconvoluted from electron density, and an interpretable elec-
tron density model was obtained (Figures 1ꢀ3). Calculated
deformation densities show the expected electron density accu-
mulations in bonding regions. Valence-shell charge concentra-
tions (VSCC) of σ-donation can also be localized by calculating
and interpreting the Laplacian of the electron density. These
results are presented for compounds 2ꢀ4 (Figures 1ꢀ3).
Complex 2 is the first example of a vanadiumꢀsilylene
complex that has been characterized by single crystal X-ray
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Figure 1. (a) ORTEP-representation of the molecular structure of 2. ADPs are depicted at the 50% probability level. Isopropyl groups and hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Si(1)ꢀC(9) 1.98452(2), Si(1)ꢀCl(1) 2.1120(8), Si(1)ꢀCl(2) 2.1264(10),
V(1)ꢀSi(1) 2.4043(7), V(1)ꢀC(1) 1.9223(2), V(1)ꢀC(4) 2.2649(3); and C(1)ꢀV(1)ꢀSi(1) 127.97(8), C(3)ꢀV(1)ꢀSi(1) 76.32(8), C(9)ꢀ
Si(1)ꢀCl(1) 98.35(7), C(9)ꢀSi(1)ꢀCl(2) 96.53(7), Cl(1)ꢀSi(1)ꢀCl(2) 99.61(3), C(9)ꢀSi(1)ꢀV(1) 129.99(7). (b) Isosurface plot of the
2
Laplacian r F(r) [eÅꢀ5] of the electron density of 2 from aspherical atom refinement with an isosurface value of 0.2 e/Å5. Phenyl, isopropyl groups, and
hydrogen atoms were omitted for clarity. The VSCCs from σ-donation are visible on the C(9)ꢀSi(1) and Si(1)ꢀV(1) bonds. (c) Deformation electron
density plot35 of 2.
Figure 2. (a) ORTEP representation of the molecular structure of 3. Anisotropic displacement parameters are depicted at the 50% probability level.
Isopropyl groups and hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Si(1)ꢀCl(2) 2.0989(4), Si(1)ꢀCl(1)
2.1127(5), C(7)ꢀSi(1) 1.96059(16), Si(1)ꢀCo(1) 2.1349(4); and Si(1)ꢀCo(1)ꢀC(6) 98.68(5), C(7)ꢀSi(1)ꢀCl(2) 101.10(4), C(7)ꢀSi(1)ꢀ
Cl(1) 96.83(4), Cl(2)ꢀSi(1)ꢀCl(1) 100.42(2), C(7)ꢀSi(1)ꢀCo(1) 121.17(4), Cl(2)ꢀSi(1)ꢀCo(1) 115.68(2), Cl(1)ꢀSi(1)ꢀCo(1) 117.88(2).
2
(b) Isosurface plot of the Laplacian r F(r) [eÅꢀ5] from nonspherical atom refinement of 3 with an isosurface value of 0.2 e/Å5. Phenyl, isopropyl
groups, and hydrogen atoms are omitted for clarity. The VSCCs from σ-donation are clearly visible on the C(5)ꢀSi(1) and Si(1)ꢀCo(1) bonds.
(c) Deformation electron density plot35 of 3.
Figure 3. (a) ORTEP representation of the molecular structure of 4. Anisotropic displacement parameters are depicted at the 50% probability level.
Isopropyl groups and hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Si(1)ꢀCl(2) 2.0890(12), Si(1)ꢀCl(1)
2.0965(14), C(5)ꢀSi(1) 1.958(3), Si(1)ꢀFe(1) 2.229(11); and Si(1)ꢀFe(1)ꢀC(4) 176.84(18), C(5)ꢀSi(1)ꢀCl(2) 101.16(12), C(5)ꢀSi(1)ꢀ
Cl(1) 99.03(12), Cl(2)ꢀSi(1)ꢀCl(1) 102.10(5), C(5)ꢀSi(1)ꢀFe(1) 121.73(12), Cl(2)ꢀSi(1)ꢀFe(1) 112.97(5), Cl(1)ꢀSi(1)ꢀFe(1) 116.92(5).
2
(b) Isosurface plot of the Laplacian r F(r) of the electron density of 4 from aspherical atom refinement with an isosurface value of 0.2 e/Å5. Phenyl,
isopropyl groups, and hydrogen atoms are omitted for clarity. The VSCCs from σ-donation are visible on C(5)ꢀSi(1) and Si(1)ꢀFe(1) bonds.
(c) Deformation electron density plot of 4.
crystallography (Figure 1a). Complex 2 crystallizes in the
monoclinic space group P2(1)/n and features a distorted
square-pyramidal geometry defined by the C5H5 centroid around
the vanadium atom. Silicon is four coordinate and displays a
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Table 1. Crystallographic Data and Structure Refinement for 2ꢀ4
2 toluene
3 0.5 benzene
4
3
3
formula
C
42H49Cl2N2O3SiV
C36H44Cl2CoN2OSi
C31H36Cl2FeN2O4Si
655.48
Fw
779.76
678
CCDC
826487
826486
826488
cryst size/mm
0.20 ꢁ 0.13 ꢁ 0.02
0.01 ꢁ 0.01 ꢁ 0.01
0.20 ꢁ 0.12 ꢁ 0.12
orthorhombic
Fdd2
cryst syst
monoclinic
orthorhombic
space group
P21/n
Pbca
T/°C
a/Å
ꢀ173
ꢀ173
ꢀ173
10.2337(2)
15.4231(3)
33.7046(11)
38.9594(13)
10.2939(4)
90
b/Å
19.3235(3)
18.8135(4)
c/Å
20.2250(4)
23.9576(4)
R/°
90
90
β/°
92.7920(10)
90
90
γ/°
90
90
90
V/Å3
3994.76(13)
6951.6(2)
13517.0(8)
1.288
Dcalcd/g cmꢀ3
1.297
1.297
Z
4
8
16
wavelength/ Å
abs coeff/mmꢀ1
θ range/°
reflns collected/indep reflns
max. and min transmn
final R1 indices
wR2 indices (all data)
largest diff peak and hole/e Å3
1.54178
1.54178
1.54178
3.907
5.842
5.661
3.16ꢀ71.94
26872/7266 [R(int) = 0.0287]
0.3674 and 0.4696
0.041
3.69ꢀ72.52
22847/6840 [R(int) = 0.0760]
0.7535 and 0.5685
0.024
3.47ꢀ71.89
25685/5420 [R(int) = 0.0730]
0.2775 and 0.4690
0.052
0.056
0.027
0.060
0.828 and ꢀ0.455
0.312 and ꢀ0.159
0.952 and ꢀ0.326
distorted tetrahedral geometry. The coordination environment
around vanadium consists of three carbonyl groups, one (η5-C5H5),
and a neutralsilylene ligand. The VꢀSi bondlength (2.4045(8) Å)
in 2 is shorter than those observed for vanadiumꢀsilyl (∼2.56 Å)
complexes,26 indicating a contribution of π-back bonding. The
ClꢀSiꢀCl bond angle in 2 (99.63(4)°) is comparable to that in 1
(97.25(6)°). The mean SiꢀCl bond length (av 2.1192(11)°) in 2
is slightly shorter than that observed for 1 (av 2.1664(16) Å),
which may be interpreted as increased Lewis acidity of the silicon
due to the σ-electron donation to the vanadium atom. The
VꢀC((η5-C5H5)) interatomic bond distances (2.250 to 2.287 Å)
are similar to the corresponding distances in vanadocene
(av 2.26 Å).36 The CꢀSiꢀV bond angle is 129.99(7)°.
distorted tetrahedral geometry. The SiꢀFe bond distance in 4
(2.2315(13) Å) is comparable to those observed in silyleneꢀ
iron complexes.17,22 The average SiꢀCl bond length
(av 2.0916(16)°) in 4 is slightly shorter than those observed
for 1 (av 2.1664(16) Å) and 2 (av 2.1192(11)°). The SiꢀC-
(carbene) bond distance (1.949(4) Å) is shorter than that
obtained for 1 (1.985(4) Å) and 2 (1.984(3) Å). The axial
SiꢀFeꢀC bond angle is almost linear (177.01(19)°).
’ CONCLUSION
A direct method to prepare dichlorosilylene complexes
IPr SiCl2 V(CO)3(η5-C5H5) (2), IPr SiCl2 Co(CO)(η5-C5H5)
3
3
3
3
(3), and IPr SiCl2 Fe(CO)4 (4) is reported. Complexes 2ꢀ4
3
3
The molecular structure of complex 3 is shown in the
Figure 2a. Complex 3 crystallizes in the orthorhombic space
group Pbca with half a benzene molecule in the asymmetric unit.
The silicon atom is four coordinate and features a distorted
tetrahedral geometry. The cobalt atom assumes distorted trigo-
nal planar coordination geometry defined by the C5H5 centroid,
the CO ligand, and the silylene (1) ligand. The CoꢀSi bond length
of 2.1348(5) Å is shorter than those reported for [Co(CO)3-
{SiCl2(IPr)}2][CoCl3(THF)] (2.2278(13) and 2.2276(12) Å).19
The SiꢀCl (av 2.1062(6) Å) and SiꢀC (1.9564(16) Å) bond
lengths are shorter than those observed in 1 (av 2.1664(16) and
1.985(4) Å). The CꢀSiꢀCo bond angle is 121.23(5)°.
have been characterized by elemental analyses and NMR spec-
troscopy. Molecular structures of 2ꢀ4 have been established by
single crystal X-ray crystallography and subsequent aspherical
atom refinement. Complex 2 is the first structurally characterized
vanadiumꢀsilylene complex. The ambiphilic nature of dichlor-
osilylene is demonstrated in TM complexes 2ꢀ4.
’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data for com-
b
plexes 2ꢀ4 as a CIF file. This material is available free of charge
via the Internet at http://pubs.acs.org.
The molecular structure of complex 4 is shown in Figure 3a.
Complex 4 crystallizes in orthorhombic space group Fdd2. The
geometry around the iron atom is distorted trigonal bipyramidal
with three equatorial positions occupied by carbonyl groups and
each of the two axial positions by a carbonyl group and a silylene
ligand. The silicon center is four coordinate and features a
’ AUTHOR INFORMATION
Corresponding Authors
*E-mail: rghadwal@uni-goettingen.de; bdittri@gwdg.de; hroesky@
gwdg.de.
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Inorganic Chemistry
ARTICLE
’ ACKNOWLEDGMENT
Wiley: New York, 1991; p 245ꢀ308; p 309ꢀ364. (c) Ogino, H. Chem.
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R.; Milstein, D. Chem.—Eur. J. 2005, 11, 2983–2988. (c) Schneider, N.;
Finger, M.; Haferkemper, C.; Bellemin-Laponnaz, S.; Hofmann, P.;
Gade, L. H. Chem.—Eur. J. 2009, 15, 11515–11529.
Financial support from the Deutsche Forschungsgemeinschaft
(Ro 224/55-3, DI 921/3-2) is gratefully acknowledged. R.A. is
thankful to the Alexander von Humboldt Stiftung for a research
fellowship.
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