Synthesis and characterization of Group 14 elements — dithienylsulfur cycloadducts and oligomers

The reactions of various organometallic dichlorides R2MCl2 (R=Bu, Ph; M=Si, Ge, Sn) with 2,2′-dilithio 3,3′-dithienylsulfur were described. They gave simultaneously cycloadducts and oligomers. The X-ray crystal structure of the heterocycle 3b shows a slightly distorted six-membered ring with the two heteroatoms (sulfur and germanium) in a boat conformation. The molecular weights of the oligomers were determined by size exclusion chromatography. Starting from metal divalent species, insoluble oligomers were obtained. The presence of bivalent metallic sites in these chains was verified by cycloaddition reaction with 3,5-di-t-butyl orthoquinone. Electrical studies show that these non-doped oligomers behave as semi-conductors.