Hydrosilylation of Aromatic Aldehydes and Ketones Catalyzed by Mono- and Tri-Nuclear Platinum(0) Complexes

Hydrosilylation of aromatic aldehydes and acetophenone with H2SiPh2 was studied by using Pt complexes as the catalyst. Reaction of aromatic aldehydes, such as PhCHO, 4-FC6H4CHO, 4-MeC6H4CHO and 4-CF3C6H4CHO with H2SiPh2 in the presence of [Pt(PPh3)3] catalyst proceeds smoothly at room temperature with similar reaction rates. The hydrosilylation of PhCHO with H2Si(C6H4-4-Me)2 proceeds faster than that with H2SiPh2. Comparison of the reactions of PhCHO with H2SiPh2 and with D2SiPh2 demonstrated a large kinetic isotope effect (3.1). The hydrosilylation of the aldehydes catalyzed by [Pt(PMe3)(μ-SiPh2)]3, reported in our previous paper, shows large dependence of the reaction rate on the aryl group of the substrate, in the order, 4-MeC6H4CHO ≫ PhCHO = 4-FC6H4CHO > 4-CF3C6H4CHO. Hydrosilylation of (3-vinyl)benzaldehyde and 10-undecenal in the presence of [Pt(PPh3)3] catalyst occurs at the carbonyl group selectively to form the corresponding alkoxysilanes. The hydrosilylation of acetophenone with H2SiPh2 catalyzed by [Pt(PPh3)3] forms 1-phenylethyl(diphenylsilyl)ether, while the reaction using the Pt3 catalyst is accompanied by dehydrosilylation to yield a mixture of the saturated and unsaturated silyl ethers.