Proton catalysis of nucleophilic substitution at pentacoordinate silicon

Addition of acid to the pentacoordinate fluorosilane 8, leads to enhanced exchange of fluorine and loss of diastereotopicity of the silicon methyl groups. A DNMR study of the 1H-NMR spectra suggests a dissociative mechanism involving protonation of the fluorine leaving group. Variable temperature studies suggest that at lower temperatures the tetracoordinate form is favoured.