Hydrosilation CatalysisBased in part on the article Hydrosilation Catalysis by John F. Harrod which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

Abstract

The addition of a hydrosilane across an unsaturated molecule is called hydrosilation. This can be catalyzed by a number of reagents among which transition metal compounds are most important. The reaction of a variety of different silanes with alkyl, alkoxy, and halogen substituents is well established. The unsaturated molecules involve alkenes, alkynes, and a huge number of different carbonyl compounds as well as combinations thereof. While hydrosilation of alkenes and alkynes can mainly be seen as a silylation method, the reaction with carbonyl compounds constitutes a formal reduction. Among the used catalyst systems hexachloroplatinic acid in isopropanol (Speier's catalyst) is most frequently used. Mechanistically the transition metal catalyzed reaction of an alkene can be seen as an oxidative addition of the silicon hydrogen bond, followed by the migratory insertion of the coordinated alkene into the metal hydrogen or silicon bond and a final reductive elimination of the alkylsilane. The formation of vinylsilanes through the dehydrogenating silation reaction is a frequently occurring side reaction. Such by‐products are thought to be formed by β‐hydride elimination of an intermediate β‐silylalkyl metal complex. The hydrosilation reaction can promote the transformation of a prochiral (alkene, ketone) to a potentially chiral molecule. It bears potential for asymmetric synthesis, which is currently heavily investigated. The reaction is equally popular for classical organic synthesis as well as for material science tasks such as the chemical bonding of a polymer to a surface.