Reactions of symmetrical and unsymmetrical disilanes in the presence of Cp2MCl2/nBuli ( M = Ti, Zr, Hf)

Article abstract of DOI:10.1016/0022-328X(96)06298-5

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 HPhMeSiSiMe₂ H 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 Si-Si bond cleavage and Si-H 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 Si-Si bond in H(SiPhMe)χH was found to be characteristic of the disilane and occurred only to a minor extent in the trisilane and was absent in the tetrasilane.