Catalytic Synthesis of Linear Oligosiloxanes and Germasiloxanes Mediated by Scandium Trifluoromethanesulfonate

Sc(OTf) 3 -catalyzed coupling reaction of silanediols with 2-methylallylsilanes and germanes leading to SiO–Si or SiO–Ge bond formation with the evolution of isobutylene is described. Diisopropyl-substituted silanediols of the general formula HO( i -Pr) 2 Si[OSi( i -Pr) 2 ] n OH ( n = 0,1) have been successfully functionalized by using 2-methylallylsilanes or 2-methylallylgermanes in the presence of scandium trifluoromethanesulfonate to yield new linear tri- and tetrasiloxanes or germasiloxanes under mild conditions. The reaction can be readily extended to the synthesis of high molecular weight polysiloxanes by using di(methylallyl)silane as a metalating agent. Unsaturated oligosiloxane products have been used as substrates for further functionalization via catalytic silylative coupling and hydrosilylation reactions.