Phosphonium Chloride Induced Dichlorosilylene Transfer from Trichlorosilane

Heating trichlorosilane with conjugated dienes or an acetylene solution at 150 or 180 ° C in the presence of a catalytic quantity of tetrabutylphosphonium chloride resulted in elimination of HCl and dichlorosilylene transfer to the unsaturated substrates to afford silacyclopentenes or 1,4-disilacyclohexa-2,5-dienes, respectively, in good to excellent yields. The trapping reaction with hex-3-yne gave 1,1,4,4-tetrachloro-2,3,5,6-tetraethyl-1,4-disilacyclohexa-2,5-diene in 79% yield, and its structure was determined by X-ray crystallography.