Dichloridobis(pyridine-2-thiol­ato-κ2 N,S)tin(IV): a new polymorph

The title compound, [SnCl₂(C₅H₄NS)₂], is the product of reaction of 2,2'-dipyridyl disulfide with tin tetra-chloride. The Sn(IV) atom adopts a distorted octa-hedral geometry, with the two bidentate pyridine-2-thiol-ate 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 C2/c with the mol-ecule having twofold rotational symmetry, the Sn(IV) atom lying on the twofold axis. The mol-ecular structure of the monoclinic polymorph is very close to that of the triclinic polymorph studied previously in space group P-1, the mol-ecule 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 inter-molecular inter-actions. In the crystal of the monoclinic polymorph, mol-ecules are bound into ribbons along the c axis by C-H⋯Cl hydrogen bonds, whereas in the crystal of the triclinic polymorph, mol-ecules form chains along the a axis by attractive S⋯S inter-actions. The crystal studied was a pseudo-merohedral twin; the refined BASF value is 0.221 (1).