PHOTOCHEMICAL-REACTIONS OF 2-(PENTAMETHYLDISILANYL)FURAN AND 2-(PENTAMETHYLDIGERMANYL)FURAN - FORMATION OF A RADICAL PAIR

Photochemical reactions of 2-(pentamethyldisilanyl)furan and 2-(pentam ethyldigermanyl)furan have been investigated by chemical trapping expe riments and laser flash-photolysis. On irradiation, the furylated cate nates of Group 14 elements undergo silicon-silicon sigma bond and germ anium-germanium sigma bond homolysis to give a pair of silyl radicals and germyl radicals, respectively. In CCl4, these radicals are convert ed to the corresponding chlorides by abstraction of a chlorine atom. I n nonhalogenated solvents (cyclohexane and other hydrocarbons), the si lyl radical pair undergoes a disproportionation to give as main produc ts a monosilane and a silene. The trimethylgermyl radical mainly coupl es at the ipso-position of the furyl group of the pairing radical to y ield the corresponding diradical. This diradical undergoes elimination of a divalent species, dimethylgermylene, with concomitant formation of 2-(trimethylgermyl)furan.