HYDROSILYLATION CATALYZED BY METAL COLLOIDS - A RELATIVE ACTIVITY STUDY

The relative activities of the platinum group metal colloids were measured for the hydrosilylation reaction between (vinyl)SiMe3 (VTMS) and (hexyl)3SiH or (EtO)3SiH. The relative activities of the colloids were the same as those reported in the literature for molecular complexes Pt > Rh > Ru = Ir ≫ Os. The synthesis of Me(decyl)Si(octyl)2 (silahydrocarbon) is discussed, and the relative activities of Pt and Rh for this reaction were compared. Rh was more active than Pt in the synthesis of silahydrocarbon from 1-octene and Me(decyl)SiH2. It was also found that aeration was critical for these reactions, consistent with the fact that hydrosilylation is cocatalyzed by O2. It was discovered in the silahydrocarbon synthesis that dihydride inhibited Pt-catalyzed hydrosilylation but had no effect on Rh. This effect was further demonstrated with model reactions that showed that, in contradiction to the literature, the relative rate of addition to olefins for R3-xSiHx addition catalyzed by Pt is R3SiH > R2SiH2. For Rh the relative rates were R2SiH2 > R3SiH; these relative rates were thus opposite those for Pt. The addition of RSiH3 to olefins was also investigated. We conclude that R2SiH2 and RSiH3 poison Pt toward catalysis while no poisoning occurs for Rh. © 1990, American Chemical Society. All rights reserved.