New Generation of Organosilyl Radicals by Photochemically Induced Homolytic Cleavage of Silicon−Boron Bonds

Unlike bis(diethylamino)organosilylboranes, bis(diisopropylamino)organosilylboranes, which have UV absorption at longer wavelength than 300 nm, undergo photolysis to afford pairs of an organosilyl radical and a bis(diisopropylamino)boryl radical by homolytic scission of the silicon-boron bonds. Generation of organosilyl radical and organoboryl radical was confirmed by trapping experiments using TEMPO (2,2,6,6-tetramethylpiperidine N-oxyl). The organosilyl radical thus generated induces not only silylation of mono-olefins and silylative cyclization of dienes but also polymerization to afford polymers bearing organosilyl termini. On the other hand, the bis(diisopropylamino)boryl radical generated is not incorporated into the olefin adducts.