Base cleavage of the benzyl–silicon bonds in m-ClC6H4CH2SiMe(OH)2 and m-ClC6H4CH2Si(OH)3. Proposed formation of metasilicate intermediates

Abstract

A kinetic study of the base-catalysed cleavage of the diol RSiMe(OH)₂(R =m-ClC₆H₄CH₂) in Me₂SO–H₂O or MeOH–H₂O has indicated that at high base concentrations the main process is the unimolecular dissociation of the dianion RSiMe(O^–)₂ into R^– and Me(O^–)SiO (an analogue of acetate ion), both of which then react rapidly with the solvent. Likewise for the triol RSi(OH)₃ in Me₂SO–H₂O the main process appears to be the formation of R^– and the metasilicate ion HO(O^–)SiO from the dianion R(OH)Si(O^–)₂. Base cleavage of the silanols RSiMe₂OH (R = PhCH₂ or m-ClC₆H₄CH₂) in Me₂SO–H₂O probably involves a contribution from the unimolecular dissociation of the anion RSiMe₂O^– to give R^– and Me₂SiO.