THE BETA-EFFECT - CHANGING THE LIGANDS ON SILICON

The ability of a silyl group to stabilize a carbocation β to silicon, the β-effect, is directly related to the electron-withdrawing ability of the groups on silicon. This was shown by using the degree of syn addition of bromine to (E)-β-silylstyrenes as a measure of the stabilizing ability. With the exception of alkoxysilanes and phenoxysilanes, a good correlation between the degree of the β-effect and the group electronegativity of the silyl group is observed. The special case of the alkoxysilanes and phenoxysilanes is discussed in the context of the addition mechanism. © 1990, American Chemical Society. All rights reserved.