Polymeric Organosilicon Systems. 26. Synthesis and Photochemical and Conducting Properties of Poly[(tetraethyldisilanylene)oligo(2,5-thienylenes)]

A series of poly[(tetraethyldisilanylene)(2,5-thienylenes) n ] ( 1 − 5 ) with n = 1−5 were synthesized. The NiCl 2 (dppe)-catalyzed Grignard coupling of 1,2-bis(5-bromothien-2-yl)tetraethyldisilane ( 6 ) and 1,2-bis(5‘-bromo-2,2‘-bithien-5-yl)tetraethyldisilane ( 7 ) with 1 equiv of Mg afforded polymer 2 ( M w = 53 000, 75% yield) and 4 ( M w = 29 500, 97% yield), respectively, while similar reaction of the di-Grignard reagent obtained from 6 and 7 with 1 equiv of 2,5-dibromothiophene afforded the respective polymers 3 ( M w = 47 000, 77% yield) and 5 ( M w = 17 000, 78% yield). The sodium condensation of 2,5-bis(chlorodiethylsilyl)thiophene afforded polymer 1 ( M w = 20 000, 32% yield). Irradiation of polymers 1 − 5 with a low-pressure mercury lamp resulted in cleavage of the silicon−silicon bonds, but the reactivity decreased with an increase in the number of thienyl units. When the films of polymers 2 − 5 were doped with FeCl 3 vapor, conductivities of doped films were determined to be 10 - 5 −10 - 3 S cm - 1 (in vacuo).