Popis: |
The reactions of disilanes with catalytic quantities of Cp2MCl2/n BuLi (M = Ti, Zr) and cis-cyclooctene in a disilane/cyclooctene/metal ratio of approximately 30: ≥ 30: 1 exhibited rapid formation of monosilanes and trisilanes. The product distributions produced from H(PhMeSi)2H, H(BuMeSi)2H (symmetrical disilanes) and from HPh2SiSiPhMeH, HPhMeSiSiMe2H, HPhMeSiSiPrMeH and HPh2SiSiPhH2 (unsymmetrical disilanes) were determined by GCMS in all cases and the trisilanes from HPh2SiSiPhMeH and HPhMeSiSiMe2H were isolated and characterized spectroscopically. Major and minor isomers of Ph4Me2Si3H2 and Ph5MeSi3H2 (formed from HPh2SiSiPhMeH) and of PhMe5Si3H2 and Ph2Me4Si3H2 (formed from HPhMeSiSiMe2H) were identified. Analysis of the product distribution in these reactions indicated that both SiSi bond cleavage and SiH dehydrocoupling of the starting disilane occurs. Rationalization of the product distributions and apparent isomer preferences through both σ-bond metathesis steps and metal silylene intermediates is presented. The rapid reaction of the SiSi bond in H(SiPhMe)xH was found to be characteristic of the disilane and occurred only to a minor extent in the trisilane and was absent in the tetrasilane. |