Dimeric and trimeric diorganosilicon chalcogenides (PhRSiE)2,3 (E = S, Se, Te; R = Ph, Me)

Ph2SiCl2 and PhMeSiCl2 react with Li2E (E = S, Se, Te) under formation of trimeric diorganosilicon chalcogenides (PhRSiE)3 (R = Ph: 1a–3a, R = Me: cis/trans-4a (E = S), cis/trans-5a (E = Se)). In case of E = S, Se dimeric four-membered ring compounds (PhRSiE)2 (R = Ph: 1b–2b, R = Me: cis/trans-4b (E = S), cis/trans-5b (E = Se)) have been observed as by-products. 1a–5b have been characterized by multinuclear NMR spectroscopy (1H, 13C, 29Si, 77Se, 125Te). Four- and six-membered ring compounds differ significantly in 29Si and 77Se chemical shifts as well as in the value of 1JSiSe. The molecular structures of 2a, 3a and trans-5a reported in this paper are the first examples of compounds with unfused six-membered rings Si3E3 (E = Se, Te). The Si3E3 rings adopt twisted boat conformations. The crystal structure of 3a reveals an intermolecular Te–Te contact of 3.858 Å which yields a dimerization in the solid state.