Crystal and Molecular Structures of the Sulfur-Rich Organic Polysulfanes Heptathiacyclononane (C₂H₄S₇) and Bis(triphenylmethyl)pentaand hexasulfane

Abstract

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 (Ph 3 C) 2 S 5 molecules consist of a helical C–S–S–S–S–S–C backbone (all torsion angles of same sign) and triphenylmethyl groups of normal conformation. The analogous (Ph 3 C) 2 S 6 forms triclinic crystals; the molecular conformation of the C–S 6 –C chains is not helical, but the motif of torsion angles is + + – – +. In both compounds the C– S bonds are considerably longer (191 pm) than comparable C–S single bonds as in cyclo-C 2 H 4 S 7 . The latter forms monoclinic crystals consisting of ring molecules of C 1 symmetry which can formally be derived from the crown-shaped S 8 ring by substituting one sulfur atom by a C 2 H 4 group of approximate C 2h symmetry.