Bromo-di(silyl)methanes - Precursors to Disilylcarbanionic Ligands

Abstract

Abstract The reaction of the series of methyl/phenylchlorosilanes Me2PhSiCl, MePh2SiCl and Ph3SiCl with CHBr3/n-BuLi to give the corresponding bromo-di(silyl)methanes has been investigated. The selectivity of the reaction proved to be strongly influenced by the number of phenyl groups bound to silicon. As already established for Me3SiCl, Si-C coupling readily occurs with Me2PhSiCl to give (Me2PhSi)2CHBr (1) in good yields, whereas MePh2SiCl affords (MePh2Si)2CHBr (2) in lower yields. The molecular structures of 2 and the by-product (MePh2Si)2CBr2 have been determ ined by single crystal X-ray diffraction. In the case of the fully arylated species, Ph3SiCl, only the monosilylated compound (Ph-Si)CH2Br (3) is generated. (HMe2Si)2CHBr (5) can be obtained starting from 1 by treatment with triflic acid to give (CF3SO3Me2Si)2CHBr (4), followed by reduction of 4 with LiAlH4 in diethyl ether. In situ metalation of 5 with n-BuLi affords (HMe2)2CHLi, which reacts instantaneously with a second equivalent of 5 to give the halogen-free dimer [(HMe2Si)2CH]SiMe2CH2SiMe2H (6).