ADDITION/ELIMINATION IN THE RHODIUM(II) PERFLUOROBUTYRATE CATALYZED HYDROSILYLATION OF 1-ALKENES - RHODIUM HYDRIDE PROMOTED ISOMERIZATION AND HYDROGENATION

Rhodium(II) perfluorobutyrate catalyzes the hydrosilylation of 1-alkenes under mild conditions, and the mode of addition determines the products that are formed. When the alkene is added to triethylsilane, ''normal'' hydrosilylation occurs; reversed addition causes the formation of allyl- or vinylsilanes. Moderate yields of isolated hydrosilylation products are obtained from reactions performed in dichloromethane. Olefin isomerization, which requires only catalytic amounts of rhodium(II) perfluorobutyrate and triethylsilane, competes with hydrosilylation, and an intermediate rhodium hydride species is responsible for this transformation. Catalytic hydrogenation of 1-alkenes occurs in dichloromethane with the use of triethysilane and alcohol. Deuterium labeling studies establish that rhodium hydride is the reagent which undergoes addition to alkenes and that the rhodium hydride is subject to rapid proton exchange. Hydrosilylation of styrene and ethyl acrylate, catalyzed by rhodium(II) perfluorobutyrate or octanoate, forms either the normal addition product or trans-disubstituted vinylsilane, depending on the mode of addition and the reaction temperature.