A silica-supported poly-y-mercaptopropylsilioxane-platinum complex has been prepared and found to catalyze the addition o f triethoxysilane to 1-hexene at 80℃ or room temperature.This complex is very stable throughout the reaction and can be reused many times without appreciable loss in the catalytic ac tivity.The addition of triethoxysilane to acetylene can also be catalyzed by this complex at room temperature to give vinyltriethoxysilane and 1

2-bis-(triethoxysilyl)-ethane.