Photochemical generation of dimethylsilylene, methyl(phenyl)silylene and diphenylsilylene in the presence of high concentrations of 1,3-butadiene leads to the formation of 1-sila-3,4-divinylcyclopentanes as major products in addition to the anticipated 1-silacyclopent-3-enes. Also obtained are the ene-reaction products from the silenes, formed by formal 1,3-silyl shifts in the bis(trimethylsilyl)arylsilanes