(Di-2-pyridyl sulfide-κ2 N,N′)diiodidozinc(II)

The title compound, [ZnI2(C10H8N2S)], contains a six-membered chelate ring adopting a boat conformation in which the Zn atom is coordinated by two iodide ions and by the two pyridyl N atoms of a single di-2-pyridyl sulfide ligand within a slightly distorted tetrahedron. The Zn, S and I atoms are located on a crystallographic mirror plane. As usual for this type of complex, the sulfide group does not participate in zinc coordination. The dihedral angle between the two pyridine rings is 60.1 (1)°.

The title compound, [ZnI 2 (C 10 H 8 N 2 S)], contains a sixmembered chelate ring adopting a boat conformation in which the Zn atom is coordinated by two iodide ions and by the two pyridyl N atoms of a single di-2-pyridyl sulfide ligand within a slightly distorted tetrahedron. The Zn, S and I atoms are located on a crystallographic mirror plane. As usual for this type of complex, the sulfide group does not participate in zinc coordination. The dihedral angle between the two pyridine rings is 60.1 (1) .

Experimental
Crystal data [ZnI 2 (C 10  Data collection: IPDS (Stoe, 1998b); cell refinement: IPDS; data reduction: IPDS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL (Bruker, 1998); software used to prepare material for publication: CIFTAB in SHELXTL. Recently, we are interested in the synthesis, structures and thermal properties of coordination polymers based on zinc (II) halides and N-donor ligands (Bhosekar et al., 2007). We have found for example that most of the ligand rich compounds can be transformed into ligand deficient compounds on heating. Starting from these findings we have initiated systematic investigations on this topic. In these investigations we have reacted zinc(II) iodine with 2,2'-bipyridyldisulfide. In this reaction, simultaneously a cleavage of the S-S bond takes place leading to the formation of di-2'pyridyl sulfide (dps). In further reaction with zinc(II) iodine the title compound (I) has been formed. To identify this product in further reaction by X-ray powder diffraction, a structure determination was performed.
In general dps is a versatile ambidentate ligand that, due to its conformational flexibility, can act in N,N'-bidentate (Tresoldi et al., 1992;Kondo et al., 1995 andNicolò et al., 1996) or bridging (Tresoldi et al., 1991 andTeles et al., 1999) coordination modes toward many metals, resulting in complexes with different stereochemistry. When dps is connected to the metal atom as a chelate ligand, a six-membered ring in boat conformation is formed, differently from its rigid analogues 2,2'-bipyridine that generates a pentacyclic chelate in a planar arragement. In addition, in some cases dps can act as tridentate ligand in a N,N,S-coordination mode involving metal-sulfur interactions (Anderson & Steel, 1998).
In the crystal structure the coordination geometry about the Zn(II) ion is almost tetrahedral with bonds being formed to two iodine ions and the two pyridyl nitrogen atoms of a single dps ligand (Fig. 1). These latter interactions result in the formation of a six-membered chelate ring, which is in a boat conformation. The angles at Zn(II) range from 93.85 to 108.33°, the largest being N-Zn-I. The Zn-I and Zn-N distances are in the range of 2.5447 (6)-2.5473 (6) and 2.063 (3) Å.
The structural parameters in the dps molecule are quite regular. In particular the C-S bond, 1.775 Å, is in good agreement with those expected for C(sp 2 )-S bonds (1.77 Å).

Experimental
ZnI 2 and 2,2'-bipyridyldisulfide was obtained from Alfa Aesar and methanol was obtained from Fluka. 0.125 mmol (39.9 mg) zinc(II) iodine, 0.125 mmol (27.6 mg) 2,2'-bipyridyldisulfide and 3 ml of methanol were transfered in test-tube, which were closed and heated to 110 °C for four days. On cooling colourless block-shaped single crystals of (I) are obtained.

Refinement
All H atoms were located in difference map but were positioned with idealized geometry and were refined isotropic with U eq (H) = 1.2 U eq (C) of the parent atom using a riding model with C-H = 0.95 Å. Fig. 1. Crystal structure of compound I with labelling and displacement ellipsoids drawn at the 50% probability level. Symmetry code: i = x, -y + 1/2, z.