CRYSTAL AND MOLECULAR-STRUCTURES OF THE SULFUR-RICH ORGANIC POLYSULFANES HEPTATHIACYCLONONANE (C2H4S7) AND BIS(TRIPHENYLMETHYL)PENTA- AND HEXASULFANE

Determination of the first structure of a chain-like polysulfane with five sulfur atoms in the chain has been attempted. Bis(triphenylmethyl )pentasulfane forms monoclinic crystals containing disordered solvent molecules preventing an accurate solution of the structure. The (Ph3C) 2S5 molecules consist of a helical C-S-S-S-S-S-C backbone (all torsion angles of same sign) and triphenylmethyl groups of normal conformatio n. The analogous (Ph3C)2S6 forms triclinic crystals; the molecular con formation of the C-S6-C chains is not helical, but the motif of torsio n angles is ++--+. In both compounds the C-S bonds are considerably lo nger (191 pm) than comparable C-S single bonds as in cyclo-C2H4S7. The latter forms monoclinic crystals consisting of ring molecules of C1 s ymmetry which can formally be derived from the crown-shaped S8 ring by substituting one sulfur atom by a C2H4 group of approximate C2h symme try.