Catalytic synthesis of oligosilazanes part 2

Abstract

Preliminary studies on transition metal-catalyzed dehydrocoupling of Si-H bonds with H-N bonds to form Si-N bonds, silazanes and H 2 are described. A number of transition metal complexes have been tested as catalyst precursors for the dehydrocoupling reaction. Of these, Ru 2(CO) 8-(Et 3Si) 2 proved to be the most active homogeneous catalyst, and Pd particles produced by the in situ reduction of Pd(OAc) 2 were the most active heterogeneous catalysts. Kinetic studies of the ruthenium-catalyzed reaction of Et 3SiH with primary amines, RNH 2 (R = n-Pr, n-Bu, s-Bu and t-Bu) were run at 70 °C in THF. The effects of changes in Et 3SiH, amine and catalyst concentrations on rates of reaction were examined. The data indicate that the dehydrocoupling catalytic cycle involves an extremely complex set of equilibria wherein the rate-determining step is dependant on the steric requirements of the amine and fragmentation of the starting Ru 3(CO) 12 cluster.