METAL COLLOID MORPHOLOGY AND CATALYTIC ACTIVITY - FURTHER PROOF OF THE INTERMEDIACY OF COLLOIDS IN THE PLATINUM-CATALYZED HYDROSILYLATION REACTION

Transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) were used to analyze the platinum colloids formed during hydrosilylation reactions. Reaction solutions were analyzed for the addition of Et3SiH to either n-hexene or neohexene catalyzed by bis{1,3diviny1,1,1,3,3-tetramethyldisiloxane}Pt0 (Karstedt's catalyst) and this analysis showed dramatic differences between the morphology of the Pt colloid formed in each case. The neohexene reaction, which gave 62% conversion to products in 1 h, contained polycrystalline, 2.5-nm-diameter Pt particles, whereas the n-hexene reaction only went to 10% conversion in 1 h and contained 1- to 1.5-nm Pt particles. The reaction of Et3SiH with styrene gave results similar to those with neohexene. © 1991.