1,3 Silicon to silicon migration of the methoxy group in solvolysis of (bromodiphenylsilyl)(methoxydimethylsilyl)bis(trimethylsilyl)methane. Crystal structures of (ethoxydimethylsilyl)(methoxydiphenylsilyl)bis(trimethylsilyl)-methane and (methoxydimethylsilyl)(methoxydiphenylsilyl)bis(trimethylsilylmethane)

Abstract

In the reaction of the bromide (Me₃Si)₂C(SiMe₂OMe)(SiPh₂Br)(1a) with EtOH the OMe group undergoes a 1,3 Si to Si migration to give exclusively the rearranged product (Me₃Si)₂-C(SiMe₂OEt)(SiPh₂OMe)(2). (The same product is obtained if AgCIO₄ is present in the MeOH.) The rate-determining step of the reaction is believed to involve separation of Br^– anchimerically assisted by the γ-OMe group to form a 1,3 methoxy-bridged cation. Because of such assistance the bromide (1a) and the related chloride (Me₃Si)₂C(SiMe₂OMe)(SiPh₂Cl) are > 10⁸ times as reactive towards MeOH as the corresponding (Me₃Si)₃C(SiPh₂X) species, but they are somewhat less reactive than the compounds (Me₃Si)₂C(SiMe₂OMe)(SiMe₂X). The reactions of (1a) with other alcohols or with water seem also to give rearranged species (Me₃Si)₂C(SiMe₂OR)(SiPh₂OMe)(R = H, CH₂Ph, CH₂CF₃).

The structures of (Me₃Si)₂C(SiMe₂OR)(SiPh₂OMe) with R = Me or Et have been determined by X-ray diffraction, and shown to involve fairly close Si–O ⋯ Si interligand contacts.