Reactions of Silylium Ions with Nucleophiles

摘要

Transformation of the diethylsilylium cation Et_2Si~+H into ethyl-and dimethylsilylium ions EtSi~+H_2 and Me_2Si~+H in reactions with nucleophiles is induced by electron-donor compounds.Their activity increases in the order Bu_2O < BuOH < (Me_3Si)_2O < C_6H_6 and is determined by the structure of the inter- mediate adduct and electron density distribution in it.Qualitative estimation shows that the affinity of the tritiated diethylsilylium cation Et_2Si~+T for a nucleophile increases in the order C_6H_6 < BuOH < Bu_2O < (Me_3Si)_2O.The higher affinity of the Et_2Si~+H cation for hexamethyldisiloxane compared to dibutyl ether,at similar basicity of the nucleophiles,is attributable to the higher charge of the oxygen atom in (Me_2Si)_2O.