Interconversion of 畏3-H2SiRR鈥?蟽-Complexes and 16-Electron Silylene Complexes via Reversible H鈥揌 or C鈥揌 Elimination
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- 作者：Mark C. Lipke ; Felix Neumeyer ; T. Don Tilley
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：April 23, 2014
- 年：2014
- 卷：136
- 期：16
- 页码：6092-6102
- 全文大小：588K
- 年卷期：v.136,no.16(April 23, 2014)
- ISSN：1520-5126
文摘
Solid samples of 畏3-silane complexes [PhBPPh3]RuH(畏3-H2SiRR鈥? (R,R鈥?= Et2, 1a; PhMe, 1b; Ph2, 1c, MeMes, 1d) decompose when exposed to dynamic vacuum. Gas-phase H2/D2 exchange between isolated, solid samples of 1c-d3 and 1c indicate that a reversible elimination of H2 is the first step in the irreversible decomposition. An efficient solution-phase trap for hydrogen, the 16-electron ruthenium benzyl complex [PhBPPh3]Ru[畏3-CH2(3,5-Me2C6H3)] (3) reacts quantitatively with H2 in benzene via elimination of mesitylene to form the 畏5-cyclohexadienyl complex [PhBPPh3]Ru(畏5-C6H7) (4). This H2 trapping reaction was utilized to drive forward and quantify the elimination of H2 from 1b,d in solution, which resulted in the decomposition of 1b,d to form 4 and several organosilicon products that could not be identified. Reaction of {[PhBPPh3]Ru(渭-Cl)}2 (2) with (THF)2Li(SiHMes2) forms a new 畏3-H2Si species [PhBPPh3]Ru[CH2(2-(畏3-H2SiMes)-3,5-Me2C6H2)] (5) which reacts with H2 to form the 畏3-H2SiMes2 complex [PhBPPh3]RuH(畏3-H2SiMes2) (1e). Complex 1e was identified by NMR spectroscopy prior to its decomposition by elimination of Mes2SiH2 to form 4. DFT calculations indicate that an isomer of 5, the 16-electron silylene complex [PhBPPh3]Ru(渭-H)(鈺怱iMes2), is only 2 kcal/mol higher in energy than 5. Treatment of 5 with XylNC (Xyl = 2,6-dimethylphenyl) resulted in trapping of [PhBPPh3]Ru(渭-H)(鈺怱iMes2) to form the 18-electron silylene complex [PhBPPh3]Ru(CNXyl)(渭-H)(鈺怱iMes2) (6). A closely related germylene complex [PhBPPh3]Ru[CN(2,6-diphenyl-4-MeC6H2)](H)(鈺怗eHtBu) (8) was prepared from reaction of tBuGeH3 with the benzyl complex [PhBPPh3]Ru[CN(2,6-diphenyl-4-MeC6H2)][畏1-CH2(3,5-Me2C6H3)] (7). Single crystal XRD analysis indicated that unlike for 6, the hydride ligand in 8 is a terminal hydride that does not engage in 3c-2e Ru鈥揌 鈫?Ge bonding. Complex 1b is an effective precatalyst for the catalytic Ge鈥揌 dehydrocoupling of tBuGeH3 to form (tBuGeH2)2 (85% yield) and H2.