PHOTOLYSIS OF ORGANOPOLYSILANES - PHOTOCHEMICAL BEHAVIOR OF BRANCHED POLYSILANES

The highly branched permethylpolysilanes, 2-(trimethylsilyl)nonamethyl tetrasilane, 2,2-bis(trimethylsilyl)octamethyltetrasilane (1b), 2,3-bi s(trimethylsilyl)octamethyltetrasilane, and ,3,3-tetrakis(trimethylsil yl)hexamethyltetrasilane (1d), and branched polysilaalkanes, 1,2-bis[t ris(trimethylsilyl)silyl]ethane, 1,3-bis[tris(trimethylsilyl)silyl]pro pane, and ,2-tetrakis(trimethylsilyl)-1,2-disilacyclopentane were prep ared, and their photochemical behavior was investigated in the presenc e or absence of 2,3-dimethylbutadiene in pentane. Irradiation of the b ranched permethylated polysilanes with a low-pressure mercury lamp pro duced two different types of silylenes, while the branched polysilaalk anes gave a single silylene. In the photolysis of 1b and 1d, hydrosila nes arising from homolytic scission of an Si-Si bond followed by the h ydrogen abstraction of the resulting silyl radicals were obtained.