Abstract
On irradiation in a chlorinated hydrocarbon containing a catalytic amount of 9, 10-dicyanoanthracene (DCA), a polysilane causes chlorinative cleavage to give the corresponding chlorosilane (s) along with hexachloroethane. Intervention of the silyl radical cation is readily rationalized by the exothermic electron transfer from a polysilane to the excited singlet state of DCA, diffusion controlled quenching of the fluorescence of DCA with a polysilane, and formation of hexachloroethane. Cationic nature of the silyl radical cation is evidenced by intramolecular nucleophilic trapping by the hydroxyl group in polysilanylalkanols under these reaction conditions. A disilane undergoes regioselective photo-silylation of aromatic nitriles in two ways, namely, substitution of the nitrile, and that of the hydrogen. The position of the silyl group introduced is closely related to the substitution pattern of the nitrile, and the spin density of the radical anion. The tetraalkyl group 14 element compounds undergo similar regioselective photo-alkyl transfer to the aromatic nitrile. The natrue of the radical cation intervened is examined by means of a radical clock technique. The similarity of the pattern of the photoinduced electron transfer reaction to that of the mass spectrum of the organic group 14 element compound is also discussed.
