Dichloridobis(pyridine-2-thiol­ato-κ²N,S)tin(IV): a new polymorph

The title compound, [SnCl₂(C₅H₄NS)₂], is the product of reaction of 2,2′-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 C2/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 P-1, 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 pseudo-merohedral twin; the refined BASF value is 0.221 (1).

[Bis(pyridin-2-yl) selenide-κ²N,N′]tetra­chloridotin(IV)

The title compound, [SnCl₄(C₁₀H₈N₂Se)], was obtained by the reaction of 2,2′-dipyridyl diselenide with tin tetra­chloride. The Sn^IV ion is coordinated by two N atoms [Sn—N = 2.266 (2) and 2.274 (2) Å] from the bis­(2-pyrid­yl)selenide ligand and four chloride anions [Sn—Cl = 2.3717 (6)–2.3939 (6) Å] in a distorted octa­hedral geometry. The central six-membered chelate ring has a boat conformation with the Se and Sn atoms deviating by 0.692 (3) and 0.855 (3) Å, respectively, from the mean plane through the remaining four ring atoms. The pyridine rings are inclined to each other by a dihedral angle of 49.62 (8)°. The crystal packing exhibits short inter­molecular Se...Cl contacts [3.5417 (7) and 3.5648 (7) Å], weak C—H...Cl hydrogen bonds and π–π stacking inter­actions between the pyridine rings with a centroid–centroid distance of 3.683 (3) Å.

1-Methyl-2,3-dihydro-1H-benzimidazole-2-selone

The title compound C₈H₈N₂Se, is the product of the reaction of 2-chloro-1-methyl­benzimidazole with sodium hydro­selenide. The mol­ecule is almost planar (r.m.s. deviation = 0.041 Å) owing to the presence of the long chain of conjugated bonds (Se=C—NMe—C=C—C=C—C=C—NH). The C=Se bond length [1.838 (2) Å] corresponds well to those found in the close analogs and indicates its pronounced double-bond character. In the crystal, mol­ecules form helicoidal chains along the b axis by means of N—H...Se hydrogen bonds.