Facile syntheses of silylene nickel carbonyl complexes from lewis base stabilized chlorosilylenes

Article abstract of DOI:10.1021/ic101556s

Two silylene nickel carbonyl complexes of composition L?Ni(CO) ₃ (1) {L = PhC(NtBu)₂SiCl} and L′₂? Ni(CO)₂ (2) { L′ = RSiCl₂, R = (1,3-bis-(2,6- diisopropylphenyl)imidazol-2-ylidene)} were prepared by

Full text of DOI:10.1021/ic101556s

Inorg. Chem. 2010, 49, 10199–10202 10199
DOI: 10.1021/ic101556s
Facile Syntheses of Silylene Nickel Carbonyl Complexes from Lewis Base
Stabilized Chlorosilylenes†
ꢀ
ꢀ
Gasper Tavcar, Sakya S. Sen, Ramachandran Azhakar, Andrea Thorn, and Herbert W. Roesky*
€
€
€
Institut fu€r Anorganische Chemie der Universitat Gottingen, Tammannstrasse 4, 37077 Gottingen, Germany
Received August 2, 2010
Two silylene nickel carbonyl complexes of composition L Ni(CO)3 (1) {L = PhC(NtBu)2SiCl} and L02 Ni(CO)2 (2)
3
3
{ L0 = RSiCl2, R = (1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene)} were prepared by reacting 1 equivalent of
Ni(CO)4 with 1 equivalent of heteroleptic chlorosilylene L for 1 and with 2 equivalents of carbene stabilized
dichlorosilylene L0 for 2 in toluene at room temperature. Both complexes 1 and 2 were characterized by single-crystal
X-ray analysis, NMR and IR spectroscopy, EI-MS spectrometry, and elemental analysis.
Introduction
the adjacent nitrogen lone pairs into empty p orbitals on
silicon, which leads to a strong stabilization of the NHSi’s.
NHSi’s can be considered as ligands having donor and
acceptor properties.5,6 As a result, they can form stable
transition metal complexes with back bonding from the metal
to the silicon center.
In 1994, West and co-workers isolated Ni(CO)2(NHSi)2
[NHSi=(tBuNCHdCHNtBu)Si] from the reaction of NHSi
with Ni(CO)4 in a molar ratio of 2:1.7 The success of this
reaction enthroned silylene as the pre-eminent ligand in
transition metal chemistry and established the concept that
NHSi’s may resemble phosphines as ligands for transition
metals. Since then, there has been a burgeoning interest
in reactions of stable silylenes with transition metals.6,8-11
Transition-metal silylene complexes are of great interest
due to their similarity to transition-metal carbene complexes
because the latter serve as extremely successful catalysts for
many organic transformations.1 In organosilicon chemistry,
these silylene metal complexes are postulated as catalytic
intermediates in a number of metal-catalyzed silylene transfer
reactions.2,3 In 1987, Tilley and co-workers reported on two
base-stabilized silylene complexes, (CO)4FeSi(OtBu)2{(O)P-
[NMe2]3} and {Cp*[Me3P]2RuSiPh2[MeCN]}þ.4 Another
promising route to prepare metal-silylene complexes is the
utilization of N-heterocyclic silylenes (NHSi’s). This ap-
proach is due to the significant p-electron donation from
† Dedicated to Professor Wolfgang Kaim on the occasion of his 60th birthday.
(5) (a) Li, R.-E.; Sheu, J.-H.; Su, M.-D. Inorg. Chem. 2007, 46, 9245–9253.
(b) Bharatam, P. V.; Moudgil, R.; Kaur, D. Inorg. Chem. 2003, 42, 4743–4749. (c)
Bharatam, P. V.; Moudgil, R.; Kaur, D. Organometallics 2002, 21, 3683–3690.
(6) Schmedake, T. A.; Haaf, M.; Paradise, B. J.; Millevolte, A. J.; Powell,
D.; West, R. J. Organomet. Chem. 2001, 636, 17–25.
(7) Haaf, M.; Hayashi, R.; West, R. J. Chem. Soc., Chem. Commun. 1994,
33–34.
(8) (a) West, R.; Denk, M. Pure Appl. Chem. 1996, 68, 785–788. (b)
Feldman, J. D.; Mitchell, G. P.; Nolte, J.-O.; Tilley, T. D. J. Am. Chem. Soc. 1998,
120, 11184–11185. (c) Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Maciejewski,
H. Organometallics 1998, 17, 5599–5601. (d) Petri, S. H. A.; Eikenberg, D.;
Neumann, B.; Stammler, H.-G.; Jutzi, P. Organometallics 1999, 18, 2615–2618. (e)
Schmedake, T. A.; Haaf, M.; Paradise, B. J.; Powell, D.; West, R. Organometallics
2000, 19, 3263–3265. (f) Dysard, J. M.; Tilley, T. D. Organometallics 2000, 19,
4726–4732. (g) Clendenning, S. B.; Gehrhus, B.; Hitchcock, P. B.; Moser, D. F.;
Nixon, J. F.; West, R. J. Chem. Soc., Dalton Trans. 2002, 484–490. (h) Amoroso,
D.; Haaf, M.; Yap, G. P. A.; West, R.; Fogg, D. E. Organometallics 2002, 21, 534–
540. (i) Avent, A. G.; Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Maciejewski, H.
J. Organomet. Chem. 2003, 686, 321–331.
*Author to whom correspondence should be addressed:
E mail:
hroesky@gwdg.de.
(1) (a) Nolan, S. P. In N-Heterocyclic Carbenes in Synthesis; Wiley-VCH:
Weinheim, Germany, 2006. (b) Glorius, F. In N-Heterocyclic Carbenes in
Transition Metal Catalysis; Springer-Verlag: Berlin, 2007. (c) Clavier, H.;
Nolan, S. P. Annu. Rep. Prog. Chem., Sect B: Org. Chem. 2007, 103, 193–
€
222. (d) Weskamp, T.; Bohm, V. P. W.; Herrmann, W. A. J. Organomet. Chem.
2000, 600, 12–22. (e) Jafarpour, L.; Nolan, S. P. Adv. Organomet. Chem. 2000,
46, 181–222. (f) Harrold, N. D.; Waterman, R.; Hillhouse, G. L.; Cundari, T. R.
J. Am. Chem. Soc. 2009, 131, 12872–12873. (g) Sinha, A.; Rahaman, S. M. W.;
Sarkar, M.; Saha, B.; Daw, P.; Bera, J. K. Inorg. Chem. 2009, 48, 11114–11122.
(h) Lee, Y.; Li, B.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 11625–11633.
(2) Lewis, K. M.; Rethwisch, D. G. In Catalyzed Direct Reactions of
Silicon; Elsevier: Amsterdam, The Netherlands, 1993.
(3) (a) Sharma, H. K.; Pannell, K. H. Chem. Rev. 1995, 95, 1351–1374. (b)
Curtis, M. D.; Epstein, P. S. Adv. Organomet. Chem. 1981, 19, 213–232. (c)
Gauvin, F.; Harrod, J. F.; Woo, H. G. Adv. Organomet. Chem. 1998, 42, 363–
405. (d) Corey, J. Y. Adv. Organomet. Chem. 2004, 51, 1–52. (e) Tilley, T. D.
Comments Inorg. Chem. 1990, 10, 37–46. (e) F€urstner, A.; Krause, H.; Lehmann,
C. W. Chem. Commun. 2001, 22, 2372–2373. (f) Calimano, E.; Tilley, T. D.
(9) Haaf, M.; Schmedake, T. A.; West, R. Acc. Chem. Res. 2000, 33, 704–
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(10) (a) Yang, W.; Fu, H.; Wang, H.; Chen, M.; Ding, Y.; Roesky, H. W.;
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Jana, A. Inorg. Chem. 2009, 48, 2058–2060. (b) Li, J.; Merkel, S.; Henn, J.;
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(4) (a) Zybill, C.; Muller, G. Angew. Chem. 1987, 99, 683–684. Ibid.
2010, 49, 775–777.
€
Angew. Chem., Int. Ed. Engl. 1987, 26, 669-670. (b) Straus, D. A.; Tilley,
T. D.; Rheingold, A. L.; Geib, S. J. J. Am. Chem. Soc. 1987, 109, 5872–5873.
(11) Meltzer, A.; Prasang, C.; Driess, M. J. Am. Chem. Soc. 2009, 131,
7232–7233.
r
2010 American Chemical Society
Published on Web 10/08/2010
pubs.acs.org/IC

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Tavcar et al.
10200 Inorganic Chemistry, Vol. 49, No. 21, 2010
The carbene transition metal complexes are serving as power-
ful catalysts for several organic transformations; therefore,
the study of silylene-metal complexes seems promising.
Moreover, such compounds may also be studied as precur-
sors for preparing silicon-metal alloys by chemical vapor
deposition.9
Scheme 1. Synthesis of 1
Recently, we reported the facile synthesis of tricoordinate
stable heteroleptic chlorosilylene PhC(NtBu)2SiCl (L)12 and
N-heterocyclic carbene stabilized dichlorosilylene (RSiCl2,
R=1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) (L0).13
These compounds can be considered as tamed silicon
dichloride14 having one or two reactive Si-Cl bonds com-
pared to other dicoordinate stable silylenes. Previously, we
also showed that tricoordinate silylene is capable of forming
silylene transition metal complexes. For example, treatment
of PhC(NtBu)2SiOtBu with Fe2(CO)9 yielded PhC(NtBu)2-
Scheme 2. Synthesis of 2
SiOtBu Fe(CO)4,10a whereas L0, when reacted with Co2-
3
(CO)8, yielded [Co(CO)3{L0}2]þ[CoCl3(THF)]-.10b To gain
further insight into the structure and bonding of silylene
units bearing unsupported Si-M bonds (M = transition
metal), we embarked on extending our investigation to
Ni(CO)4. Unlike chromium hexacarbonyl (d6, saturated), iron
pentacarbonyl (d8, saturated), and cobalt carbonyl (d9, un-
saturated), Ni(CO)4 (d10, saturated) is the most labile and
most reactive toward ligand exchange. The rate of exchange is
first order, and proportional to the concentration of Ni-
(CO)4.15 Very recently, Driess et al. documented the formation
(Scheme 1), whereas in L0, the reaction proceeds with 1:2
equivalents to afford L02Ni(CO)2 (2) with the displace-
ment of two CO molecules (Scheme 2). Both products are
extremely air- and moisture-sensitive and immediately
decompose when exposed to air. Complexes 1 and 2 are
soluble in solvents like diethyl ether, toluene, and THF.
The number of carbonyl groups displaced from Ni(CO)4
might be due to electronic factors of the ligand. A prac-
tical consequence is that the elimination of CO can be
fine-tuned by alteration of the substituents on the nitro-
gen atoms of the silylene ligand.
The coordination of the Ni atom to silicon resulted in a
downfield chemical shift in the 29Si NMR spectrum. The
silylene-nickel complex of 1 resonates at δ 62.69 ppm
(29Si NMR of L: 14.16 ppm), while in 2 it is observed at
δ 43.19 ppm (29Si NMR of L0: 19.06 ppm). The downfield
chemical shift is due to the deshielding upon coordination
of the nickel atom to silicon. These values are consistent
with those reported for base-stabilized silylene transition
of silylene-nickel carbonyl complex R0Si Ni(CO)3 [R =
3
CH[(C=CH2)CMe(NAr)2], Ar=2,6-iPr2C6H3]11 and showed
its remarkable reactivity toward H2S, NH3, iPrNH2, and
H2NNH(Ph).16 In all of these reactions, the Ni(CO)3
group played the role of an umbrella by using the lone
pair of electrons of silicon. In view of these results, we
selected Ni(CO)4 and probed its reaction with L and L0,
respectively.
Results and Discussion
Synthetic and Spectroscopic Aspects. The synthetic
strategy for the title compounds involves the one-pot
reaction of Ni(CO)4 with the starting materials L and
L0, respectively. In L, the silicon exhibits a tricoordinate
site (2N, 1Cl) and can act as a two-electron donor. In L0,
the silicon is stabilized by an N-heterocyclic carbene and
features a tricoordinate center with a lone pair of elec-
trons on silicon (1C, 2Cl). The reactions of Ni(CO)4 with
L and L0 are straightforward, which afforded silylene
nickel carbonyl complexes 1 and 2, respectively. In case of
L, the reaction proceeds from a 1:1 molar ratio to afford
metal complexes (δ 40.30 ppm for PhC(NtBu)2SiOtBu
3
Fe(CO)4 and δ 44.25 ppm for [Co(CO)3{L0}2]þ[CoCl3-
1
(THF)]-).10a,b The H NMR spectrum of 1 exhibits two
sets of resonances: one for tBu and another for phenyl
protons [δ 1.06 ppm (1H NMR of L: 1.08 ppm) and δ
6.71-6.95 ppm (1H NMR of L: 6.78-7.05 ppm)],
whereas in 2 the -CH(CH3)2 protons resonate at 0.96
and 1.51 ppm (1H NMR for -CH(CH3)2 of L0: 1.01 and
1.43 ppm), -CH(CH3)2 at 2.94 ppm (1H NMR for -CH-
(CH3)2 of L0: 2.79 ppm), and NCH at 6.23 ppm (1H NMR
for NCH of L0: 6.36 ppm). The 13C NMR spectrum
reveals the presence of carbonyl groups, resonating at δ
199.31 ppm for 1 and δ 202.51 ppm for 2. Compound 1
shows the molecular ion in the EI-MS spectrum at m/z 438,
while compound 2exhibitsonlyfragments. The COstretch-
ing frequencies for 1 (1984 cm-1 and 1969 cm-1) and for 2
(1974 cm-1 and 1921 cm-1) are very close to the reported
CO stretching frequencies for previously mentioned silylene
metal carbonyl complexes and deviate significantly from
that of Ni(CO)4 (2060 cm-1).17 On the basis of these wave
numbers, we can argue that the C-O bond energy in 1 is
L Ni(CO)3 (1), where one carbonyl group was displaced
3
(12) (a) So, C.-W.; Roesky, H. W.; Magull, J.; Oswald, R. B. Angew.
Chem. 2006, 118, 4052–4054. Ibid. Angew. Chem., Int. Ed. 2006, 45,
3948-3950. (b) Sen, S. S.; Roesky, H. W.; Stern, D.; Henn, J.; Stalke, D.
J. Am. Chem. Soc. 2010, 132, 1123–1126.
(13) Ghadwal, R. S.; Roesky, H. W.; Merkel, S.; Henn, J.; Stalke, D.
Angew. Chem. 2009, 121, 5793–5796. Ibid. Angew. Chem., Int. Ed. 2009, 48,
5683 - 5686.
(14) (a) Schmeisser, M.; Voss, P. Z. Anorg. Allg. Chem. 1964, 334, 50–56.
(b) Koe, J. R.; Powell, D. R.; Buffy, J. J.; Hayase, S.; West, R. Angew. Chem.
1998, 110, 1514–1515. Ibid. Angew. Chem., Int. Ed. 1998, 37, 1441-1442. (c)
Weidenbruch, M. Angew. Chem. 2006, 118, 4347–4348. Ibid. Angew. Chem.,
Int. Ed. 2006, 45, 4241 - 4242.
(15) Hegedus, L. S. In Transition Metals in the Synthesis of Complex
Organic Molecules; University Science Books: Mill Valley, CA, 1994.
€
(16) Meltzer, A.; Inoue, S.; Prasang, C.; Driess, M. J. Am. Chem. Soc.
(17) Braga, D.; Grepioni, F.; Orpen, A. G. Organometallics 1993, 12,
1481–1483.
2010, 132, 3038–3046.

Article
Inorganic Chemistry, Vol. 49, No. 21, 2010 10201
observed a variation of the bond lengths and the angles of
the ligand when coordinated to nickel. For comparison are
˚
giventhebondlengthof Si-Cl in 1, 2.1149(7) A [Si-Cl of L
˚
2.156(1) A], and the cone angle (—N-Si-N) is 71.210(2)ꢀ
[—N-Si-N of L 71.15(7)ꢀ].12a The Si-Clav distance in 2 is
0
˚
˚
2.1280(9) A [Si-Clav of L 2.1664(17) A], and —Cl-Si-
Clav is 98.63(4)ꢀ [—Cl-Si-Clav in L0 97.25(6)ꢀ].13
Conclusion
The chlorosilylenes L and L0 are versatile ligands for the
synthesis of silylene nickel carbonyl complexes. The nature of
the ligand indicates the displacement of carbonyl groups from
the Ni(CO)4 under the same experimental conditions. In the
case of L, one carbonyl group is displaced to yield L Ni(CO)3
3
(1), but with L0, two carbonyl groups are displaced to yield
Figure 1. Crystal structure of 1. Hydrogen atoms are omitted for clarity.
˚
L02 Ni(CO)2 (2). The above versatile and diverse nature of two
Selected bond lengths (A) and angles (deg): Ni1-Si1 2.2111(8), Ni1-C10
3
1.795(2), Ni1-C11 1.7967(19), Ni1-C12 1.798(2), Cl1-Si1 2.1149(7),
Si1-N1 1.8456(15), Si1-N2 1.8373(15); C10-Ni1-C11 114.39(9),
C10-Ni1-C12 114.47(9), C11-Ni1-C12 110.48(8), C10-Ni1-Si1
102.67(7), C11-Ni1-Si1 105.66(6), C12-Ni1-Si1 108.31(6), N2-
Si1-N1 71.15(7), N2-Si1-Cl1 102.23(5), N1-Si1-Cl1 102.24(5), N2-
Si1-Ni1 123.18(5), N1-Si1-Ni1 125.63(5), Cl1-Si1-Ni1 120.87(3),
N2-Si1-C26 35.72(6), N1-Si1-C26 35.81(6), Cl1-Si1-C26 109.08(5).
silylenes can be utilized as a scaffold for the preparation of other
different transition metal silylene complexes. Moreover, one can
also pursue the reactivities of 1 and 2 with reactive Si-Cl bonds
after coordinating to the lone pair of electrons, which will
provide synthetic access to other fascinating silicon compounds.
Experimental Section
slightly higher compared to that of 2. This result is con-
sistent with the π-bonding argument, which states that
greater positive charge on nickel results in less back bond-
ing of electron density into the π* orbitals of the CO ligand.
Structural Characterization. The molecular structures
of 1 and 2 are shown in Figures 1 and 2. Important bond
lengths and angles are provided in the legends of the
figures. Both compounds crystallize in the monoclinic
P21/c space group (Table 1). In both structures, the silicon
atoms are tetra-coordinate and adopt distorted tetrahe-
dral geometry. In 1, the four sites are occupied by two
nitrogen atoms from the amidinato ligand, one chlorine,
and one nickel atom, while in 2 they are occupied by one
carbon, two chlorine, and one nickel atom. In both
compounds, Ni also displays distorted tetrahedral geo-
metry. In 1, the coordination environment at the Ni atom
is derived from one Si and three C atoms of the carbonyl
groups, but 2 features a coordination environment of two
Si and two C atoms of the carbonyl groups. The Si-Ni
All manipulations were carried out in an inert atmosphere
of dinitrogen using standard Schlenk techniques and in a
dinitrogen-filled glovebox. Solvents were purified using the
MBRAUN solvent purification system MB SPS-800. All
chemicals were purchased from Aldrich and used without
further purification. L and L0 were prepared as proposed
in the literature,12b,13 as was Ni(CO)4.18 1H, 13C, and 29Si
NMR spectra were recorded with a Bruker Avance DPX 200
or a Bruker Avance DRX 500 spectrometer, using C6D6 as a
solvent. Chemical shifts δ are given relative to SiMe4. EI-MS
spectra were obtained using a Finnigan MAT 8230 instru-
ment. IR spectra were recorded on Bio-Rad Digilab FTS7
spectrometer in the range 4000-350 cm-1 as nujol mulls.
€
Elemental analyses were performed by the Institut fur Anor-
€
ganische Chemie, Universitat Gottingen. Melting points were
measured in a sealed glass tube on a Buchi B-540 melting point
€
€
apparatus.
Synthesis of 1. The prepared 0.64 M solution of Ni(CO)4 in
diethyl ether (1.75 mL, 1.12 mmol) was added to the solution of
L (0.31 g, 1.05 mmol) in toluene (50 mL) at ambient tempera-
ture. The color of the solution changed slowly from yellow to
colorless. The mixture was stirred overnight. The reaction
mixture was then filtered through Celite, and the solution was
concentrated and stored at 4 ꢀC overnight to yield colorless
crystals of 1 (0.25 g, 54.5%). Mp 168-175 ꢀC. Elemental
analysis (%) calcd for C18H23ClN2NiO3Si (438): C, 49.40; H,
5.30; N, 6.40. Found: C, 50.71; H, 5.95; N, 6.68. 1H NMR (200
MHz, C6D6, 25 ꢀC): δ 1.06 (s, 18H, C(CH3)3), 6.71-6.95 (m, 5H,
C6H5) ppm. 13C{1H} NMR (125.75 MHz, C6D6, 25 ꢀC): δ 30.87
C(CH3)3, 54.8 (C (CH3)3), 125.64, 127.81, 128.0, 128.65, 129.28,
130.94 (C6H5), 171.13 (NCN), 199.31 (CO) ppm. 29Si{1H} NMR
(99.36 MHz, C6D6, 25 ꢀC): δ 62.69 ppm. EI-MS: m/z 438 (100%).
FT-IR (Nujol, cm-1): wave number 1984 (s), 1969 (s).
˚
˚
bond length in 1 is 2.2111(8) A. In 2, they are 2.1955(9) A
˚
and 2.1854(7) A. These bond lengths are comparable
with those of other silylene nickel complexes.7,16
˚
The Si-Ni bonds in the two complexes are 0.14 A and
0.16 A shorter than the sum of the covalent radii of Si
˚
˚
(1.11 A) and Ni (1.24 A). A similar decrease in bond
˚
length is also observed in the Si-Fe bond in the PhC-
10a
˚
(NtBu)2SiOtBu Fe(CO)4 (2.23 A) complex,
which is
0.2 A shorter than the sum of the covalent radii of Si (1.11
3
˚
˚
˚
˚
A) and Fe (1.32 A)þand the Si-Co bond (2.22 A) in
- 10b
[Co(CO)3{SiCl2 L0}2] [CoCl3(THF)] , which is 0.15 A
˚
shorter compared to the sum of covalent radii of silicon
and cobalt. These results indicate some possible π-back-
bonding within the Ni-Si bond. There is a slight change
in the Ni-C bond lengths when compared with that of the
precursor. The average Ni-C bond length in Ni(CO)4 is
Synthesis of 2. The prepared 0.64 M solution of Ni(CO)4 in
diethyl ether (1.75 mL, 1.12 mmol) was added to the solution of
L0 (1.09 g, 2.24 mmol) in toluene (50 mL) at ambient tempera-
ture. The color of the solution changed slowly from brown to
yellow. The mixture was stirred for 12 h. The reaction mixture
was then filtered through Celite, and the solution was concen-
trated and stored at room temperature overnight to yield bright
17
˚
1.817(2) A, whereas in 1, the Ni-Cav bond distance is
˚
1.796(2) A. The deviation is more in 2, where the mean
yellow crystals of 2 toluene (0.89 g, 73%). Mp 165-170 ꢀC. For
3
˚
Ni-C bond length is 1.764(2) A. A similar kind of
variation is also observed in the Ni-C bonds of Ni(CO)2-
(18) Jolly, P. W.; Wilke, G. In The Organic Chemistry of Nickel; Academic
Press: New York, 1974.
(NHSi)2 [NHSi=(tBuNCHdCHNtBu)Si].7 Moreover, we

ꢀ
Tavcar et al.
10202 Inorganic Chemistry, Vol. 49, No. 21, 2010
˚
Figure 2. Crystal structure of 2 toluene. Hydrogen atoms and one toluene molecule are omitted for clarity. Selected bond lengths (A) and angles (deg):
3
Ni-C2 1.764(2), Ni-C1 1.765(3), Ni-Si2 2.1854(7), Ni-Si1 2.1955(9), Si1-C9 1.985(2), Si1-Cl11 2.1183(8), Si1-Cl12 2.1443(10), Si2-C19 2.002(2),
Si2-Cl22 2.1197(8), Si2-Cl21 2.1296(9); C2-Ni-C1 125.81(11), C2-Ni-Si2 111.44(7), C1-Ni-Si2 97.59(7), C2-Ni-Si1 110.41(8), C1-Ni-Si1 107.18(8),
C19-Si2-Cl22 100.15(7), C19-Si2-Cl21 99.58(7), Cl22-Si2-Cl21 97.67(4), C19-Si2-Ni 116.02(6), Cl22-Si2-Ni 122.01(3), Cl21-Si2-Ni 117.39(3).
Table 1. Crystal and Structure Refinement Parameters for Compounds 1 and 2
with a rotating anode generator and Incoatec Helios optics
˚
using Cu KR radiation (λ=1.54178 A). Both crystals belonged
parameter
1
2 toluene
to the space group P21/c and were intergrated with SAINT.19
Empirical absorption correction was applied by SADABS,20
and the structure solution by direct methods as well as refine-
ment were executed using SHELX.21
3
empirical formula
fw
C18H23ClN2NiO3Si C63H80Cl4N4NiO2Si2
437.61
1182.0
monoclinic
P21/c
crystal system
space group
monoclinic
P21/c
For 1, a colorless plate of 0.3 ꢀ 0.3 ꢀ 0.01 mm was mounted
and a total of 36 195 reflections measured, of which 3491 were
independent. The asymmetric unit consisted of one molecule of
the amidinate silylene nickel carbonyl complex. All atoms
except hydrogens were refined anisotropically by full-matrix
least-squares methods on F2 to give a final R factor of 2.75%.
Hydrogen atoms were refined using a riding model.21
For 2, the crystal selected was a brownish plate of 0.15 ꢀ 0.1 ꢀ
0.04 mm size. A total of 101 205 reflections were collected, of
which 11 010 were unique. The asymmetric unit consisted of one
molecule of 2 and one molecule of toluene. The latter was
disordered to a high degree around the 2-fold axis. The disorder
was resolved into five positions in the asymmetric unit; their
occupancy was refined and fixed in later stages of the refine-
ment. All non-hydrogen atoms were refined anisotropically by
full-matrix least-squares methods on F2 to yield a final R factor
of 4.89%. Hydrogen atoms were refined using a riding model.21
˚
a (A)
13.942(3)
11.524(2)
13.737(3)
111.24(3)
2057.2(7)
4
15.072(3)
17.701(4)
24.500(5)
95.46(3)
6507(2)
4
˚
b (A)
˚
c (A)
β (deg)
3
V (A )
˚
Z
F
calcd (g/cm3)
F(000)
1.413
912
1.207
2504
μ (mm-1
)
3.278
1.147
2.624
1.059
GOF on F2
R1 [I > 2σ(I)]
R1, wR2 (all data)
largest diff peak/hole (e A
0.0271, 0.0753
0.0275, 0.0755
0.332/-0.228
0.0391, 0.1066
0.0489, 0.1146
0.537/-0.290
-3
˚
)
elemental analysis, 2 toluene was treated under vacuum condi-
3
tions overnight to remove the toluene molecule. Anal. calcd for
C56H72Cl4N4NiO2Si2 (885.34): C, 61.71; H, 6.66; N, 5.14.
Found: C, 59.89; H, 6.84; N, 4.49. 1H NMR (200 MHz, C6D6,
25 ꢀC): δ 0.96 (d, 24 H, J = 6.7 Hz, CH(CH3)2), 1.51 (d, 24 H,
J = 6.7 Hz, CH(CH3)2), 2.94 (sept, 4H, CH(CH3)2), 6.23 (s, 4H,
CH), 6.95-7.26 (m, 12 H, C6H3) ppm. 13C{1H} NMR (125.75
MHz, C6D6, 25 ꢀC): δ 23.22 (CH(CH3)2), 25.76 (CH(CH3)2), 29.33
(CH(CH3)2), 124.36 (NCH), 125.64, 124.95, 125.64, 128.51 129.28,
130.92, 135.17, 145.55, 163.58 (C6H3), 202.51 (CO) ppm. 29Si{1H}
NMR (99.36 MHz, C6D6, 25 ꢀC): δ 43.19 ppm. FT-IR(Nujol,
cm-1): wave number 1974 (s), 1921 (s).
Acknowledgment. We are thankful to the Deutsche Forschungs-
gemeinschaft for supporting this work. G.T. and R.A. are thankful to
the Alexander von Humboldt Stiftung for research fellowships.
Supporting Information Available: CIFs for 1 and 2. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(19) SAINT; Bruker AXS Inc.: Madison, WI, 2000.
€
€
€
(20) Sheldrick, G. M. SADABS; Universitat Gottingen: Gottingen,
Germany, 2000.
Crystal Structure Determination. Crystals were mounted at
100 K on a Bruker Smart 6000 CCD diffractometer equipped
(21) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.