Homogeneous hydrosilylation, transition mechanism

The mechanism for hydrosilylation in Figs. 6 and 7 clearly has much in common with suggestions regarding homogeneous transition metal catalysis for other processes involving olefins, such as hydrogenation, isomerization, the oxo reaction, and oligo- and polymerization. 

A proposed mechanism [9] for the hydrosilylation of olefins catalyzed by platinum(II) complexes (chloroplatinic acid is thought to be reduced to a plati-num(II) species in the early stages of the catalytic reaction) is similar to that for the rhodium(I) complex-catalyzed hydrogenation of olefins, which was advanced mostly by Wilkinson and his co-workers [10]. Besides the Speier s catalyst, it has been shown that tertiary phosphine complexes of nickel [11], palladium [12], platinum [13], and rhodium [14] are also effective as catalysts, and homogeneous catalysis by these Group VIII transition metal complexes is our present concern. In addition, as we will see later, hydrosilanes with chlorine, alkyl or aryl substituents on silicon show their characteristic reactivities in the metal complex-catalyzed hydrosilylation. Therefore, it seems appropriate to summarize here briefly recent advances in elucidation of the catalysis by metal complexes, including activation of silicon-hydrogen bonds. 

A review on the industrial applications of homogeneous catalysts is particularly welcome. The proceedings of recent symposia and a general text have been published in addition to reviews on metal cluster catalysts, activation of saturated hydrocarbons by metal complexes in solution, catalysis by arene Group-VIB tricarbonyls, titanocene-catalysed reactions ofalkenes, transition-metal hydrides in catalysis, the mechanisms of the catalytic cyclization of aliphatic, hydrocarbons, asymmetric hydrosilylation and asymmetric synthesis. A n.m.r. study of the conformations of chelated Diop and a MO study of organo-metallic migration reactions are also of interest. Polymer supported catalysts have been reviewed and the relationship between cross-linking of the polymer and catalytic activity has been discussed. ... 

---