Hydrosilylasjon

Hydrosilylation is a chemical reaction in which a silicon–hydrogen (Si–H) bond adds across a carbon–carbon multiple bond, typically an alkene or an alkyne, to form a carbon–silicon bond. It is a foundational transformation in organosilicon chemistry and is widely used to synthesize silicon-containing compounds and to modify polymers and materials.

Most commonly, hydrosilylation is catalyzed by transition metals. Platinum-, rhodium-, palladium-, nickel-, and iridium-based systems have been developed, with the platinum-based Karstedt catalyst being particularly well known for its efficiency. The generally accepted mechanism involves oxidative addition of the Si–H bond to the metal, migratory insertion of the unsaturated substrate into the metal–silicon bond, and reductive elimination to form the new Si–C bond and regenerate the catalyst. For alkenes, the reaction usually proceeds with anti-Markovnikov regioselectivity, placing silicon at the less substituted carbon, though catalyst design can influence both regiochemistry and stereochemistry. Hydrosilylation of alkynes typically gives vinylsilane products, with further functionalization possible.

Applications of hydrosilylation are broad. It is used to prepare organosilicon intermediates, to crosslink and cure silicone polymers, and to functionalize surfaces and complex polymers. In silicone technology, hydrosilylation enables network formation and tailoring of mechanical and thermal properties. The method also supports selective modifications in organic synthesis, enabling the introduction of silyl groups as protective or directing handles and as versatile synthetic handles for downstream transformations.

Challenges and variations continue to be developed. Enantioselective hydrosilylation uses chiral catalysts to access optically active silicon-containing products. Substrate scope, catalyst longevity, and environmental considerations influence catalyst choice, with ongoing research aimed at expanding efficiency and compatibility.