POLYMERIC ORGANOSILICON SYSTEMS .22. SYNTHESIS AND PHOTOCHEMICAL PROPERTIES OF POLY[(DISILANYLENE)OLIGOPHENYLYLENES] AND POLY[(SILYLENE)BIPHENYLYLENES]

[4,4'-(tetramethyldisilanylene)biphenylylene](1a), poly[4,4'-(tetraeth yldisilanylene)-biphenylylene] (1b), and 2-dimethyl-1,2-diphenyldisila nylene)biphenylylene] (1c) were prepared by the condensation reaction of the respective 4,4'-bis(chlorosilyl)biphenyls with sodium. Poly[4,4 '-(dimethylsilylene)biphenylylene] (1d), poly[4,4'-(methylphenylsilyle ne)biphenylylene] (1e), and poly[3,3'-(dimethylsilylene)biphenylylene] (1f) were obtained from the nickel-catalyzed dehalogenative coupling of the products formed from the reaction of the respective bis(bromoph enyl)-substituted silanes with magnesium. Poly[(disilanylene)terphenyl ylenes] 2a-c and poly[(disilanylene)quaterphenylylenes] 3a-c were also synthesized by the similar nickel-catalyzed dehalogenative coupling r eactions of di-Grignard re agents prepared from the respective bis(4-b romophenyl)-substituted disilanes, with p-dibromobenzene and 4,4'- dib romobiphenyl, respectively. The disilanylene-substituted polymers 1a-c , 2a-c, and 3a-c were found to be photoactive. Irradiation of the thin solid films prepared from these polymers in air resulted in scission of the Si-Si bonds, leading to the formation of degradation products i ncluding silanol and siloxy units. Poly[(silylene)biphenylylenes] 1d-f were found to be inert toward UV irradiation. Photochemical behavior of the disilanylene-substituted polymers was also investigated in solu tion, and photoactivities of these polymers were found to decrease wit h increasing the degree of an extension of the ct-electron system. The results of crystal orbital calculations for poly[(disilanylene)oligop henylylenes] have also been reported.