Dichloridobis(pyridine-2-thiolato-kappa(2) N,S)tin(IV): a new polymorph

The title compound, [SnCl2(C5H4NS) (2)], is the product of reaction of 2,20-dipyridyl disulfide with tin tetrachloride. The Sn IV atom adopts a distorted octahedral geometry, with the two bidentate pyridine-2-thiolate ligands forming two planar four-membered chelate rings. The two Sn-Cl, two Sn-N and two Sn-S bonds are in cis, cis and trans configurations, respectively. The crystal grown from acetonitrile represents a new monoclinic polymorph in space group C-2/c with the molecule having twofold rotational symmetry, the Sn IV atom lying on the twofold axis. The molecular structure of the monoclinic polymorph is very close to that of the triclinic polymorph studied previously in space group P1, the molecule occupying a general position [Masaki & Matsunami (1976). Bull. Chem. Soc. Jpn, 49, 3274-3279; Masaki et al. (1978). Bull. Chem. Soc. Jpn, 51, 3298-3301]. Apparently, the formation of the two polymorphs is determined by the different systems of intermolecular interactions. In the crystal of the monoclinic polymorph, molecules are bound into ribbons along the c axis by C-H ... Cl hydrogen bonds, whereas in the crystal of the triclinic polymorph, molecules form chains along the a axis by attractive S - S interactions. The crystal studied was a pseudomerohedral twin; the refined BASF value is 0.221 (1).