Kay A. Youngdahl

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 3 Si) 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 3 SiH 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 3 SiH, 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.

New Catalytic Routes to Preceramic Polymers: Ceramic Precursors to Silicon Nitride and Silicon-Carbide Nitride

Abstract : Pyrolysis of a set of silicon and nitrogen substituted polysilazanes are conducted under a set of standard conditions (5 degrees C/min to 900 degrees C in a nitrogen atmosphere). The apparent ceramic compositions and ceramic yields for pyrolyzed samples of the polysilazanes (Ph(H)SiNH)x, (C6H13(H)SiNH)x, (Me(H)SiNH)x, and (H2SiNMe)x are determined. Preliminary conclusions concerning structure/reactivity relationships are discussed based on the pyrolysis results. Keywords: Polysilazanes, Structure/reactivity relationships, Catalysis, Synthesis, Pyrolysis, New catalytic reactions. Reprints.