Reactivity Studies of Heteroleptic Silylenes with N2O - ACS Publications

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Reactivity Studies of Heteroleptic Silylenes with N2O Ramachandran Azhakar, Kevin Pröpper, Birger Dittrich,* and Herbert W. Roesky* Institut für Anorganische Chemie der Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany S Supporting Information *

ABSTRACT: Reaction of heteroleptic silylenes LSiX (L = PhC(NtBu)2; X = PPh2 (1), NPh2 (2), NMe2 (3), OtBu (4)) with N2O resulted in the oxidized dimeric product [LSi(X)(μ-O)]2 (X = PPh2 (5), NPh2 (6), NMe2 (7), OtBu (8)), which contains a four-membered Si2O2 ring. Compounds 5−8 were characterized by spectroscopic and spectrometric techniques. The molecular structures of 5−8 were established by single-crystal X-ray structure analysis.

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INTRODUCTION The taming of highly reactive species to isolate them as stable species under laboratory conditions is a difficult task in synthetic chemistry.1 Carbenes and silylenes R2E: (where R = alkyl, aryl, H, or halogen and E = C or Si) are such highly reactive species. They play a role of growing importance in synthetic organic and organosilicon chemistry as well as in material sciences.2−4 Initially silylenes had been recognized as short-lived species in the gas phase, in solution, or trapped in frozen matrices.5 They feature both nucleophilic and electrophilic reactive sites at the silicon atom. Owing to the presence of two nonbonding electrons in the HOMO and an empty porbital as the LUMO, silylenes show Lewis acid as well as Lewis base properties.6 The first remarkable divalent silicon tencoordinate π complex, (Me5C5)2Si, was reported by Jutzi and co-workers in 1986.7 In 1994 West et al. isolated the first stable N-heterocyclic silylene (NHSi).8 The NHSis are considered as analogues of N-heterocyclic carbenes (NHCs), while the latter have been studied widely and found diverse applications in chemistry.9,10 They are used as excellent σ-donor ligands to stabilize compounds with unusual oxidation states.11 Many remarkable reactivity studies such as insertion, addition, metal complexes, and Lewis acids of stable NHSis with a variety of substrates have been reported.12−20 In 2006, we made a first report on a base-stabilized monochlorosilylene LSiCl (L = PhC(NtBu)2).21 Further, we stabilized dichlorosilylene as NHC·SiCl2 (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol2-ylidene or 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) without using hazardous reducing agents such as alkali metals or KC8. NHC·SiCl2 was obtained by a new synthetic procedure comprising the reductive elimination of HCl from trichlorosilane in the presence of NHC under mild reaction conditions.22 Recently we reported on a facile synthesis of heteroleptic silylenes that were prepared by the metathesis reaction of alkali metal amide, phosphide, alkoxide, or organoalkyl reagents with amidinato ligand stabilized monochlorosilylene LSiCl [L = PhC(NtBu)2] in toluene as solvent.23 Nitrous oxide is an effective donor of oxygen that has been © XXXX American Chemical Society

widely used for carrying out catalytic oxidation reactions. Treatment of LSiCl with N2O resulted in the formation of the trimer [LSi(μ-O)Cl]3, which contains a Si3O3 six-membered ring.20a However, the reaction of LSitBu with N2O yielded the dimeric product with a Si2O2 four-membered ring.23a Driess et al. reported the NHC-supported silanone upon reaction of N2O with the adduct of NHC-silylene.24a In contrast to the reactivity studies of N2O with silylenes, Severin et al. isolated a covalently bonded nitrous oxide of NHC.24b In order to explore the chemistry of the heteroleptic silylenes, we passed dry N2O gas through a toluene solution of the heteroleptic silylene LSiX (X = PPh2 (1), NPh2 (2), NMe2 (3), OtBu (4)).

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RESULTS AND DISSCUSSION Compounds [LSi(X)(μ-O)]2 (X = PPh2 (5), NPh2 (6), NMe2 (7), OtBu (8)) were obtained by passing dry N2O gas through a toluene solution of heteroleptic silylene LSiX (X = PPh2 (1), NPh2 (2), NMe2 (3), OtBu (4)) for 15 minutes at room temperature (Scheme 1). Compounds 5−8 are stable both in the solid state and in solution for a long time without any decomposition under an inert gas atmosphere. The 29Si NMR spectrum of 5 exhibits two resonances of a doublet centered at δ −88.33 and −88.35 ppm (JSiP = 33 Hz), which is upfield shifted compared to that of 1 (δ 34.3, JSiP = 152 Hz), consistent with compounds containing five-coordinate silicon.23b The 31P NMR spectrum of compound 5 shows a broad resonance (δ −51.95 ppm), with two silicon satellites of JSiP = 33 Hz. The tBu protons for compound 5 in its 1H NMR spectrum appear as a singlet (δ 0.92 ppm). Compounds 6−8 exhibit two resonances, δ −108.09 and −108.17 (6), −99.44 and −100.16 (7), and −113.39 and −113.99 (8) ppm, respectively, in their 29Si NMR spectrum. The narrow resonances in the 29Si NMR chemical shifts of compounds 6−8 might be due to the five-membered rings being in opposite Received: September 15, 2012

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dx.doi.org/10.1021/om3008794 | Organometallics XXXX, XXX, XXX−XXX

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Scheme 1. Synthesis of Compounds 5−8

directions to each other. The 1H NMR spectra of 6−8 also show two resonances of equal intensity for tBu protons, which reside over the nitrogen atoms. Again these two resonances exhibit very little difference, which might be due to the slightly different geometrical orientation of the two silicon atoms in the molecule. Compounds 5−7 each display their fragment ion [M+ − X] in its mass spectrum at m/z 735 (X = PPh2 (5)), 718 (X = NPh2 (6)), and 594 (X = NMe2 (7)), respectively. The mass spectrum of compound 8 displays its molecular ion peak at m/z 696. The molecular structures for compounds 5−8 are given in Figures 1−4. In all cases the silicon atom is five-coordinate and Figure 2. Molecular structure of 6. The anisotropic displacement parameters are depicted at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (deg): N2−Si1 1.8356(10), N1−Si1 1.9514(11), N3−Si1 1.7663(10), O1−Si1 1.6750(9), O1*−Si1 1.7131(9); N1−Si1−N2 68.96(4), N2− Si1−N3 111.82(5), N1−Si1−N3 95.49(5), O1−Si1−O1* 84.73(4), O1−Si1−N2 121.01(5), O1*−Si1−N2 100.27(4), O1−Si1−N1 91.27(4), N1−Si1−O1* 164.41(5), O1−Si1−N3 125.43(5), Si1− O1−Si1* 95.27(4).

Å). Similarly, two types of Si−O bond lengths are present. The shorter bond length is 1.6703(10) Å, and the longer one measures 1.7205(10) Å. These shorter and longer bond lengths are corresponding to the axial and equatorial positions. The Si1−P1 bond distance in 5 is 2.2895(6) Å, which is shorter compared to that of 1 (2.3111(6) Å).23b The Si−O−Si and O− Si−O bond angles are 94.69(5)° and 85.32(5)°. The coordination environments of 6 and 7 are derived from the three nitrogen atoms and two oxygen atoms. Like 5, there are two types of Si−N (amidinato ligand) and Si−O bond lengths present in 6 and 7. The Si1−N3 bond distance is 1.7663(10) Å in 6. The Si1−N3 and Si2−N4 bond distances in 7 are 1.7271(13) and 1.7259(13) Å,26 which are comparable to that of 3 (1.724(2) Å).27 The Si−O−Si and O−Si−O bond angles are 95.27(4)° and 84.73(4)° in 6. In 8, the coordination environment of silicon is derived from three oxygen atoms and two nitrogen atoms. The Si1−O3 and Si1−O4 bond distances are 1.6445(10) and 1.6422(10) Å.

Figure 1. Molecular structure of 5. The anisotropic displacement parameters are depicted at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (deg): N2−Si1 1.8248(12), N1−Si1 1.9824(12), P1−Si1 2.2895(6), O1−Si1 1.6703(10), O1*−Si1 1.7205(10); N1−Si1−N2 68.62(5), N2−Si1−P1 119.60(4), N1−Si1−P1 93.94(4), O1−Si1−O1* 85.32(5), O1−Si1−N2 121.53(5), O1*−Si1−N2 102.40(5), O1− Si1−N1 92.19(5), N1−Si1−O1* 167.60(5), Si1−O1−Si1* 94.69(5).

arranged in a distorted trigonal bipyramidal geometry with a τ value25 (τ = 1 for perfect trigonal bipyramidal; τ = 0 for perfect square based pyramid) of 0.77 (5), 0.65 (6), {0.65 for both Si1 and Si2} (7), and {0.70 for Si1 and 0.67 for Si2} (8). The coordination environment features two nitrogen atoms from the supporting amidinato ligand, two oxygen atoms, and one phosphorus atom for 5. The four-membered Si2O2 ring in 5 is slightly distorted from planarity. There are two types of Si−N (amidinato ligand) bond lengths present, one being shorter (Si1−N2 1.8248(12) Å) and one longer (Si1−N1 1.9824(12)

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CONCLUSION In summary we report on the reactivity of heteroleptic silylene, LSiX (X = PPh2 (1), NPh2 (2), NMe2 (3), OtBu (4)) with N2O, which afforded the dimeric product [LSi(X)(μ-O)]2 (X = PPh2 (5), NPh2 (6), NMe2 (7), OtBu (8)) containing a Si2O2 six-membered ring. This result is in contrast to the trimer [LSi(Cl)(μ-O)]3 obtained from the reaction of LSiCl with B

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Figure 3. Molecular structure of 7. The anisotropic displacement parameters are depicted at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (deg): N2−Si1 1.8370(12), N1−Si1 2.0020(13), N3−Si1 1.7271(13), O1−Si1 1.6688(11), O2−Si1 1.7240(11), N5−Si2 1.8369(12), N6−Si2 2.0116(12), N4−Si2 1.7259(13), O1−Si2 1.7265(11), O2−Si2 1.6724(11); N1−Si1−N2 67.58(5), N2−Si1−N3 114.87(6), N1−Si1−N3 96.60(6), O1−Si1−O2 85.08(5), O1−Si1−N2 120.39(6), O2−Si1−N2 99.09(5), O1−Si1−N1 90.48(5), O1−Si1−N3 122.53(6), O2−Si1−N1 161.22(5), N5−Si2−N6 67.51(5), N4−Si2−N5 115.98(6), N4−Si2−N6 96.37(6), O1−Si2−O2 84.89(5), O2−Si2−N5 118.61(6), O1−Si2−N5 99.51(6), O1−Si2−N6 90.44(5), O1−Si2−N6 161.90(5), O2−Si2−N4 123.18(6), Si1−O1−Si2 95.03(6), Si2−O2−Si1 95.00(5).

Figure 4. Molecular structure of 8. The anisotropic displacement parameters are depicted at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (deg): N2−Si1 1.8477(12), N1−Si1 1.9801(11), O3−Si1 1.6445(10), O1−Si1 1.6738(9), O2−Si1 1.7149(9), N3−Si2 1.8428(11), N4−Si2 1.9723(11), O4−Si2 1.6422(10), O2−Si2 1.6744(9), O1−Si2 1.7198(9); N1−Si1−N2 68.09(5), N2−Si1−O1 121.58(5), N1−Si1−O3 90.82(5), O1−Si1−O2 84.98(4), O1−Si1−N2 121.58(5), O2−Si1−N2 100.75(5), O1−Si1−N1 90.58(5), O2−Si1−N1 163.37(5), N3−Si2−N4 68.04(5), N3−Si2−O1 99.33(5), N3−Si2−O2 122.77(5), O1−Si2−O2 84.80(4), O2−Si2−O4 122.25(5), O1−Si2−N4 162.45(5), O2−Si2−N4 91.93(5), Si1−O1−Si2 95.01(5), Si2−O2−Si1 95.18(5). Compound 5. Quantity used: LSiPPh2, 1.00 g. Yield: 0.92 g, 89%. Anal. (%) Calcd for C54H66N4O2P2Si2 (921.25): C, 70.40; H, 7.22; N, 6.08. Found: C, 70.31; H, 7.12; N, 6.01. 1H NMR (500 MHz, CD2Cl2, 25 °C): δ 0.92 (b, 36H, C(CH3)3), 7.20−7.96 (m, 30H, ArH) ppm. 31 1 P{ H} NMR (202.46 MHz, CD2Cl2, 25 °C): δ −51.95 (b, JSiP = 33 Hz) ppm. 29Si{1H} NMR (99.36 MHz, CD2Cl2, 25 °C): δ −88.33 (d, JSiP = 33 Hz), −88.35 (d, JSiP = 33 Hz) ppm. EI-MS: m/z 735 [M+ − PPh2]. Compound 6. Quantity used: LSiNPh2, 1.05 g. Yield: 0.95 g, 87.3%. For elemental analysis, 6·toluene was treated under vacuum for six hours to remove the toluene molecules. Anal. (%) Calcd for C54H66N6O2Si2 (887.31): C, 73.09; H, 7.50; N, 9.47. Found: C, 73.06; H, 7.42; N, 9.45. 1H NMR (500 MHz, CDCl3, 25 °C): δ 0.89 (s, 18H, C(CH3)3), 0.92 (s, 18H, C(CH3)3), 6.96−7.60 (m, 30H, ArH) ppm. 29 Si{1H} NMR (99.36 MHz, CDCl3, 25 °C): δ −108.09 (s), −108.17 (s) ppm. EI-MS: m/z 718 [M+ − NPh2]. Compound 7. Quantity used: LSiNMe2, 1.10 g. Yield: 0.93 g, 80%. Anal. (%) Calcd for C34H58N6O2Si2 (639.03): C, 63.90; H, 9.15; N, 13.15. Found: C, 63.83; H, 9.13; N, 13.03. 1H NMR (500 MHz, CDCl3, 25 °C): δ 1.08 (s, 18H, C(CH3)3), 1.13 (s, 18H, C(CH3)3), 2.72 (s, 6H, N(CH3)2), 2.74 (s, 6H, N(CH3)2), 7.24−7.38 (m, 10H,

N2O, containing a six-membered Si3O3 ring. The formation of the dimers is obviously due to the presence of bulkier X = PPh2 (1), NPh2 (2), NMe2 (3), OtBu (4) groups on the silicon atoms.

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EXPERIMENTAL SECTION

Syntheses were carried out under an inert atmosphere of dinitrogen in oven-dried glassware using standard Schlenk techniques. All other manipulations were accomplished in a dinitrogen-filled glovebox. Solvents were purified by an MBraun solvent purification system, MB SPS-800. Compounds 1−4 were prepared as reported in the literature.23b 1H and 29Si NMR spectra were recorded with a Bruker Avance DPX 300 or a Bruker Avance DRX 500 spectrometer, using CD2Cl2 and CDCl3 as solvents. Chemical shifts δ are given relative to SiMe4. EI-MS spectra were obtained using a Finnigan MAT 8230 spectrometer. Elemental analyses were performed at the Institut für Anorganische Chemie, Universität Göttingen. General Procedure for the Synthesis of [LSiX(μ-O)]2 (X = PPh2 (5), NPh2 (6), NMe2 (7), OtBu (8)). Toluene (60 mL) was added to a 100 mL Schlenk flask containing the respective heteroleptic silylene compounds. Dry N2O gas was passed through this solution for 15 min. C

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ArH) ppm. 29Si{1H} NMR (99.36 MHz, CDCl3, 25 °C): δ −99.44 (s), −100.16 (s) ppm. EI-MS: m/z: 594 [M+ − NMe2]. Compound 8. Quantity used: LSiOtBu, 1.00 g. Yield: 0.90 g, 86%. Anal. (%) Calcd for C38H64N4O4Si2 (697.11): C, 65.47; H, 9.25; N, 8.04. Found: C, 65.43; H, 9.22; N, 8.03. 1H NMR (500 MHz, CDCl3, 25 °C): δ 1.11 (s, 18H, C(CH3)3), 1.14 (s, 18H, C(CH3)3), 1.42 (s, 9H, OC(CH3)3), 1.46 (s, 9H, OC(CH3)3), 7.22−7.35 (m, 10H, ArH) ppm. 29Si{1H} NMR (99.36 MHz, CDCl3, 25 °C): δ −113.39 (s), −113.99 (s) ppm. EI-MS: m/z: 696 [M+], 639 [M+ − C(CH3)3], 623 [M+ − OC(CH3)3]. Crystal Structure Determination. Suitable single crystals for Xray structural analysis of 5−8 were obtained by storing their corresponding toluene solutions at 0 °C for 24−48 h in the refrigerator (Table S1). Crystals were taken out of the mother liquor under an argon atmosphere using NVH oil. Diffraction data were collected at 100 K on a Bruker three-circle diffractometer equipped with a SMART 6000 CCD area detector and a Cu Kα rotating anode. Due to good crystal quality, all four data sets were collected to the edge of the Ewald sphere with high completeness and high multiplicity. Raw data were integrated with SAINT,28 and an empirical absorption correction with SADABS29 was applied. The structures were solved by direct methods (SHELXS-97) and refined against F2 by full-matrix least-squares methods using all data (SHELXL-2012).30 SHELXLE31 was used as refinement GUI. All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were refined unconstrained with displacement parameters constrained to 1.2 or 1.5 of the Uiso of their parent atom. Compounds 5 and 8 showed rotational disorder in their tert-butyl groups. Disordered groups were assigned to different part numbers to suppress intermolecular bonds, and H atoms of these groups were calculated and constrained to their parent atom sites. Compound 6 contains one toluene molecule with a rotating methyl group.

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ASSOCIATED CONTENT

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AUTHOR INFORMATION

Nakagawa, T.; Kawai, T. Coord. Chem. Rev. 2010, 254, 2643−2651. (e) Guerchais, V.; Ordronneau, L.; Bozec, H. L. Coord. Chem. Rev. 2010, 254, 2533−2545. (5) Gaspar, P. P.; West, R. In The Chemistry of Organic Silicon Compounds, 2nd ed.; Rappoport, Z.; Apeloig, Y., Eds.; John Wiley and Sons: NewYork, 1999; Vol. 2, Part 3, pp 2463−2568. (6) (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. (d) Percival, P. W.; Brodovitch, J.-C.; Mozafari, M.; Mitra, A.; West, R.; Ghadwal, R. S.; Azhakar, R.; Roesky, H. W. Chem.Eur. J. 2011, 17, 11970−11973. (e) Inoue, S.; Epping, J. D.; Irran, E.; Driess, M. J. Am. Chem. Soc. 2011, 133, 8514−8517. (f) Inoue, S.; Wang, W.; Präsang, C.; Asay, M.; Irran, E.; Driess, M. J. Am. Chem. Soc. 2011, 133, 2868−2871. (g) Ghadwal, R. S.; Azhakar, R.; Roesky, H. W.; Pröpper, K.; Dittrich, B.; Goedecke, C.; Frenking, G. Chem. Commun. 2012, 48, 8186−8188. (7) Jutzi, P.; Kanne, D.; Krüger, C. Angew. Chem. 1986, 98, 163−164; Angew. Chem., Int. Ed. 1986, 25, 164. (8) Denk, M.; Lennon, R.; Hayashi, R.; West, R.; Belyakov, A. V.; Verne, H. P.; Haaland, A.; Wagner, M.; Metzler, N. J. Am. Chem. Soc. 1994, 116, 2691−2692. (9) (a) Nolan, S. P. In N-Heterocyclic Carbenes in Synthesis; WileyVCH: 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) Solorio-Alvardo, C. R.; Wang, Y.; Echavarren, A. M. J. Am. Chem. Soc. 2011, 133, 11952−11955. (e) Boyd, P. D. W.; Wright, J.; Zafar, M. N. Inorg. Chem. 2011, 50, 10522−10524. (f) Hess, J. L.; Hsieh, C.-H.; Reibenspies, J. H.; Darensbourg, M. Y. Inorg. Chem. 2011, 50, 8541−8552. (g) Jana, A.; Azhakar, R.; Tavčar, G.; Roesky, H. W.; Objartel, I.; Stalke, D. Eur. J. Inorg. Chem. 2011, 3686−3689. (h) Kronig, S.; Theuergarten, E.; Holschumacher, D.; Bannenberg, T.; Daniliuc, C. G.; Jones, P. G.; Tamm, M. Inorg. Chem. 2011, 50, 7344−7359. (10) (a) Chuprakov, S.; Malik, J. A.; Zibinsky, M.; Fokin, V. V. J. Am. Chem. Soc. 2011, 133, 10352−10355. (b) Dzik, W. I.; Zhang, P.; de Bruin, B. Inorg. Chem. 2011, 50, 9896−9903. (c) Goedecke, C.; Leibold, M.; Siemeling, U.; Frenking, G. J. Am. Chem. Soc. 2011, 133, 3357−3569. (d) Martin, D.; Melaimi, M.; Soleilhavoup, M.; Bertrand, G. Organometallics 2011, 30, 5304−5313. (11) Wang, Y.; Robinson, G. H. Inorg. Chem. 2011, 50, 12326− 12337. (12) Yao, S.; van Wüllen, C.; Sun, X.-Y.; Driess, M. Angew. Chem. 2008, 120, 3294−3297; Angew. Chem., Int. Ed. 2008, 47, 3250−3253. (13) (a) Meltzer, A.; Inoue, S.; Präsang, C.; Driess, M. J. Am. Chem. Soc. 2010, 132, 3038−3046. (b) Jana, A.; Schulzke, C.; Roesky, H. W. J. Am. Chem. Soc. 2009, 131, 4600−4601. (c) Jana, A.; Schulzke, C.; Roesky, H. W.; Samuel, P. P. Organometallics 2009, 28, 6574−6577. (d) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Wolf, H.; Stalke, D. Organometallics 2012, 31, 5506−5510. (14) (a) Yao, S.; Brym, M.; van Wüllen, C.; Driess, M. Angew. Chem. 2007, 119, 4237−4240; Angew. Chem., Int. Ed. 2007, 46, 4159−4162. (b) Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Heinicke, J.; Boese, R.; Bläser, D. J. Organomet. Chem. 1996, 521, 211−220. (c) Haaf, M.; Schmiedl, A.; Schmedake, T. A.; Powell, D. R.; Millevolte, A. J.; Denk, M.; West, R. J. Am. Chem. Soc. 1998, 120, 12714−12719. (15) Xiong, Y.; Yao, S.; Brym, M.; Driess, M. Angew. Chem. 2007, 119, 4595−4597; Angew. Chem., Int. Ed. 2007, 46, 4511−4513. (16) (a) Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Slootweg, J. C. Chem. Commun. 2000, 1427−1428. (b) Antolini, F.; Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Slootweg, J. C. Dalton. Trans. 2004, 3288−3294. (17) Xiong, Y.; Yao, S.; Driess, M. Organometallics 2009, 28, 1927− 1933. (18) (a) Xiong, Y.; Yao, S.; Driess, M. Chem.Eur. J. 2009, 15, 5545−5551. (b) Xiong, Y.; Yao, S.; Driess, M. Organometallics 2010, 29, 987−990. (c) Ghadwal, R. S.; Azhakar, R.; Roesky, H. W.; Pröpper, K.; Dittrich, B.; Klein, S.; Frenking, G. J. Am. Chem. Soc. 2011, 133,

S Supporting Information *

CIF files for 5 (CCDC 900209), 6 (CCDC 900210), 7 (CCDC 900211), and 8 (CCDC 900212) and a table giving crystal data and details of the structure solution and refinement for 5−8. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author

*E-mail: [email protected]; [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the Deutsche Forschungsgemeinschaft (DFG) for supporting this work. R.A. is grateful to the Alexander von Humboldt Stiftung for a research fellowship.

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REFERENCES

(1) Gaspar, P. P. In Reactive Intermediates, Vol. 3; Jones, M., Jr., Moss, R. A., Eds.; Wiley: New York, 1985; pp 333−427. (2) (a) Gil, W.; Trzeciak, A. M. Coord. Chem. Rev. 2011, 255, 473− 483. (b) Zhang, W.-H.; Chien, S. W.; Hor, T. S. A. Coord. Chem. Rev. 2011, 255, 1991−2024. (c) Troegel, D.; Stohrer, J. Coord. Chem. Rev. 2011, 255, 1642−1685. (3) (a) Levason, W.; Reid, G; Zhang, W. Coord. Chem. Rev. 2011, 255, 1319−1341. (b) Gaspar, P. P.; West, R. In The Chemistry of Organic Silicon Compounds, 2nd ed.; Rappoport, Z.; Apeloig, Y., Eds.; John Wiley and Sons: NewYork, 1999; Vol. 2, Part 3, pp 2463−2568. (4) (a) Vollmer, C.; Janiak, C. Coord. Chem. Rev. 2011, 255, 2039− 2057. (b) Hui, J. K.-H.; Maclachlan, M. J. Coord. Chem. Rev. 2010, 254, 2363−2390. (c) Steffen, A.; Ward, R. M.; Jones, W. D.; Marder, T. B. Coord. Chem. Rev. 2010, 254, 1950−1976. (d) Hasegawa, Y.; D

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Organometallics

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17552−17555. (d) Gehrhus, B.; Hitchcock, P. B. Organometallics 2004, 23, 2848−2849. (e) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Hey, J.; Stalke, D. Organometallics 2011, 30, 3853−3858. (f) Azhakar, R.; Sarish, S. P.; Tavčar, G.; Roesky, H. W.; Hey, J.; Stalke, D.; Koley, D. Inorg. Chem. 2011, 50, 3028−3036. (g) Azhakar, R.; Sarish, S. P.; Roesky, H. W.; Hey, J.; Stalke, D. Organometallics 2011, 30, 2897− 2900. (h) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Hey, J.; Stalke, D. Dalton Trans. 2012, 41, 1529−1533. (i) Azhakar, R.; Roesky, H. W.; Ghadwal, R. S.; Holstein, J. J.; Dittrich, B. Dalton Trans. 2012, 41, 9601−9603. (19) (a) Azhakar, R.; Sarish, S. P.; Roesky, H. W.; Hey, J.; Stalke, D. Inorg. Chem. 2011, 50, 5039−5043. (b) Tavčar, G.; Sen, S. S.; Azhakar, R.; Thorn, A.; Roesky, H. W. Inorg. Chem. 2010, 49, 10199−10202. (c) Ghadwal, R. S.; Azhakar, R.; Pröpper, K.; Holstein, J. J.; Dittrich, B.; Roesky, H. W. Inorg. Chem. 2011, 50, 8502−8508. (d) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Wolf, H.; Stalke, D. J. Am. Chem. Soc. 2012, 134, 2423−2428. (e) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Hey, J.; Stalke, D. Chem. Asian J. 2012, 7, 528−533. (f) Schmedake, T. A.; Haaf, M.; Paradise, B. J.; Millevolte, A. J.; Powell, D.; West, R. J. Organomet. Chem. 2001, 636, 17−25. (g) Azhakar, R.; Roesky, H. W.; Holstein, J. J.; Dittrich, B. Dalton Trans. 2012, 41, 12096−12100. (20) (a) Azhakar, R.; Tavčar, G.; Roesky, H. W.; Hey, J.; Stalke, D. Eur. J. Inorg. Chem. 2011, 475−477. (b) Jana, A.; Azhakar, R.; Sarish, S. P.; Samuel, P. P.; Roesky, H. W.; Schulzke, C.; Koley, D. Eur. J. Inorg. Chem. 2011, 5006−5013. (21) So, C.-W.; Roesky, H. W.; Magull, J.; Oswald, R. B. Angew. Chem. 2006, 118, 4052−4054; Angew. Chem., Int. Ed. 2006, 45, 3948− 3950. (22) Ghadwal, R. S.; Roesky, H. W.; Merkel, S.; Henn, J.; Stalke, D. Angew. Chem. 2009, 121, 5793−5796; Angew. Chem., Int. Ed. 2009, 48, 5683−5686. (23) (a) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Wolf, H.; Stalke, D. Chem. Commun. 2012, 48, 4561−4563. (b) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Wolf, H.; Stalke, D. Organometallics 2012, 31, 4588−4592. (24) (a) Xiong, Y.; Yao, S.; Driess, M. J. Am. Chem. Soc. 2009, 131, 7562−7563. (b) Tskhovrebov, A. G.; Solari, E.; Wodrich, M. D.; Scopelliti, R.; Severin, K. Angew. Chem. 2012, 124, 236−238; Angew. Chem., Int. Ed. 2012, 51, 232−234. (25) (a) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349−1356. (b) Chandrasekhar, V.; Azhakar, R.; Senapati, T.; Thilagar, P.; Ghosh, S.; Verma, S.; Boomishankar, R.; Steiner, A.; Kögerler, P. Dalton Trans. 2008, 1150−1160. (26) Chandrasekhar, V.; Boomishankar, R.; Azhakar, R.; Gopal, K.; Steiner, A.; Zacchini, S. Eur. J. Inorg. Chem. 2005, 1880−1885. (27) So, C.-W.; Roesky, H. W.; Gurubasavaraj, P. M.; Oswald, R. B.; Gamer, M. T.; Jones, P. G.; Blaurock, S. J. Am. Chem. Soc. 2007, 129, 12049−12054. (28) SAINT, Bruker AXS Inc.: Madison, WI, USA), 2000. (29) Sheldrick, G. M. SADABS; Universität Göttingen: Germany, 2000. (30) Sheldrick, G. M. Crystallogr. Sect. A 2008, 64, 112−122. (31) Huebschle, C. B.; Sheldrick, G. M.; Dittrich, B. J. Appl. Crystallogr. 2011, 44, 1281−1284.

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dx.doi.org/10.1021/om3008794 | Organometallics XXXX, XXX, XXX−XXX