POLYMERIC ORGANOSILICON SYSTEMS .14. SYNTHESIS AND SOME PROPERTIES OFALTERNATING POLYMERS COMPOSED OF A DITHIENYLENE GROUP AND A MONO-SILANYLENE, DI-SILANYLENE OR TRI-SILANYLENE UNIT

Poly[5,5' - (dimethylsilylene) - 2,2' - dithienylene] (4a), oly[5,5'-( methylphenylsilylene)-2,2'-dithienylene] (4b), 1,1,2,2-tetramethyldisi lanylene)2,2'-dithienylene] (4c), methyl-1,2-diphenyldisilanylene)-2,2 -dithienylene] (4d), ,2,2,2-tetrametbyldisilanylene)-2,2'-dithienylene l (4e), and poly[5,5'-(1,1,2,2,3,3 - hexamethyltrisilanylene) - 2,2'-d ithienylenel were synthesized by dehalogenative coupling of the respec tive bis(2-bromothienyl)-substituted mono, di- and tri-silanes with ma gnesium in the presence of a catalytic amount of a nickel(II) complex in 16-99% yields. The polymers thus obtained are light-yellow solids a nd soluble in common organic solvents. Molecular weights, M(w), of the polymers were measured and found to be 7800-35 000 by gel-permeation chromatography relative to polystyrene standards. The photochemical pr operties of the polymers (4a-4d) having silylene and disilanylene unit s were investigated. Only ethyl-1,2-diphenyl-disilanylene)2,2'-dithien ylenel (4d) was found to be photoactive, but the others were inactive. When the thin solid films prepared from the polymers 4a-4e by spin-co ating were exposed to antimony(V) fluoride in vacuo, the films became conducting; their conductivities were determined to be 10(-2)-10(-3) S cm-1 by the four-probe method.