Collect. Czech. Chem. Commun. 1980, 45, 2085-2099

Steric effects in hydrosilylation of styrene

Gabriela Kuncová and Václav Chvalovský

Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, 165 02 Prague 6-Suchdol


Hydrosilylation of styrene, 2-phenyl-1-propene, trans-1-phenyl-1-propene by (CH3)R2SiH (R = C2H5, i-C3H7, i-C4H9) and R'3SiH (R' = i-C3H7, t-C4H9) in the presence of [RhCl.{P(C6H5)3}3] (I), [{RhCl(C2H4)2}2] (II) and H2PtCl6 as catalysts has been studied. The reaction of styrene with (CH3)R2SiH catalysed by complex I in benzene leads to α- and β-adduct as well as to a substitution product. Analogous addition of (i-C3H7)3SiH catalysed by complexes I and II produces selectively trans-1-triisopropylsilyl-2-phenylethylene. Reaction of 2-phenyl-1-propene with CH3(C2H5)2SiH gives 1-diethylmethylsilyl-2-phenylpropane, 1-diethylmethylsilyl-2-phenyl-2-propene and 1-diethylmethylsilyl-2-phenyl-1-propene. Hydrosilylation of trans-1-phenyl-1-propene by diethylmethylsilane catalysed by complex I gave 1-diethylmethylsilyl-2-phenylpropane and 3-diethylmethylsilyl-1-phenylpropane. Conversion of 2-phenyl-1-propene and trans-1-phenyl-1-propene in their reaction with diethylmethylsilane catalysed by complex I was found to be much lower compared to the reaction with styrene and attained maximum at 60°C. The selectivity and rates of above reactions can be influenced by the presence of air oxygen.