Silica-supported Karstedt-type Catalyst For Hydrosilylation Reactions

Hydrosilylation is one of the most important reactions in organosilicon chemistry and organic synthesis, and many silicones containing special functional groups have been synthesized via this reaction. In this paper, the preparation, properties, catalytic kinetics and use as a hydrosilylation catalyst of a silica-supported Karstedt (Pt) type catalyst are reported, and the preparation technology for Methyl(r-chloropropyl) dichlorosilane was studied by this catalyst.Karstedt's catalyst, Pt2{[(CH2=OH)Me2Si]2O}3, is a particularly efficient homogeneous catalyst for hydrosilylation. Herein we report preparation of a heterogeneous catalyst which is modeled after the Karstedt catalyst. Vinylsiloxane groups have been bonded to the surface of fume silica by treatment with vinyltriethoxysilane. Further treatment of this material with an aqueous solution of chloroplatinic acid leads to formation of a heterogeneous Karstedt like catalyst. The content of platinum in catalyst was 1.9% by AAS detection. This type of catalyst has high catalytic activity at room temperature under an atmospheric pressure, and the catalyst can be reused five times without any appreciable loss in the catalytic activity. . Catalytic kinetics of hydrosilylation of Me2PhSiH with styrene was studied, and the activation energy of this was calculated to be 93.32 kJ/mol. It was found that the main product was B-addition product and there were rarely a-addition product when dimethylphenylsilane reacted with styrene. The highly regioselective result indicated that the silica-supported Karstedt catalyst have good selectivity. The mechanism of hydrosilylation was also investigated, and study suggested the Chalk-Harrod mechanism is possible catalytic mechanism catalyzed by this catalyst.Methyl(y-chloropropyl)dichlorosilane was prepared by using the catalyzing of silica-supported Karstedt catalyst for the catalyzing hydrosilation ofmethyldichlorosilane with 3-chloro propene. The effect of various possible facts and the reaction conditions on the results was also investigated. It was found that the catalyst has high activity under 0.5g. The prdduct is obtained in 78% yield.