hydrosilation

Hydrosilation, more commonly called hydrosilylation, is a chemical reaction in which a silicon–hydrogen bond (Si–H) adds across a carbon–carbon multiple bond, typically an alkene or alkyne, to form a silicon–carbon (Si–C) bond. The process is typically catalyzed by a transition-metal complex, with platinum-based systems being the most widely used, although other metals such as nickel, rhodium, and palladium can also catalyze hydrosilylation under suitable conditions. It is a fundamental step in the preparation of organosilicon compounds and in the curing and modification of silicone polymers.

In most catalytic cycles, the Si–H bond undergoes oxidative addition to the metal center, followed by coordination of the unsaturated substrate. The substrate then inserts into a metal–hydride or metal–silicon bond, and reductive elimination furnishes the Si–C bond and regenerates the active catalyst. The reaction can exhibit considerable chemoselectivity and regioselectivity, depending on the substrate and catalyst.

Applications of hydrosilation are broad. In polymer chemistry, it is used to crosslink vinyl-terminated silicone polymers with Si–H crosslinkers to form silicone elastomers and coatings. It also enables the synthesis of a wide range of organosilicon compounds and the surface modification of materials, providing routes to adhesion promoters, coatings, and functionalized polymers. Industrially important catalysts include the Karstedt catalyst and Speier’s catalyst, with reaction conditions typically designed to balance reactivity, selectivity, and tolerance to moisture. Safety considerations include the handling of reactive Si–H reagents and air-sensitive catalysts.