[Bis(pyridin-2-yl) selenide-κ2 N,N′]tetrachloridotin(IV)

The title compound, [SnCl4(C10H8N2Se)], was obtained by the reaction of 2,2′-dipyridyl diselenide with tin tetrachloride. The SnIV 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.

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.  (Tresoldi et al., 1992;Kondo et al., 1995;Blake et al., 2002;Teles et al., 2006;Zhao et al., 2007;Wriedt et al., 2008aWriedt et al., , 2008bWriedt et al., , 2008c. The important structural feature of these complexes is the practically unchangeable bond angle at sulfur atom. On the other hand, the most labile geometrical parameters in them are the dihedral angle between two pyridine rings as well as the deviation of metal atom from the mean plane of the central six-membered chelate ring passed through the two nitrogen and two carbon atoms due to the different coordination environment. It is interesting to note that 2,2′-dipyridyl selenide is also known (Dunne et al., 1995), however, no structurally characterized metal complexes with this ligand were reported till now.
This article is dedicated to the first structural characterization of metal complex with 2,2′-dipyridyl selenide ligand - respectively. Two pyridine rings are inclined to each other with a dihedral angle of 49.62 (8)°. Remarkably, the value of the bond angle at selenium atom in I (101.51 (10)°) is almost equal to that in the free 2,2′-dipyridyl selenide ligand (101.9 (2)°) (Dunne et al., 1995).

Experimental
A solution of SnCl 4 (0.13 g, 0.5 mmol) in CH 2 Cl 2 (25 ml) was added to a solution of 2,2′-dipyridyl diselenide (0.16 g, 0.5 mmol) in CH 2 Cl 2 (25 ml) with stirring at room temperature. After 10 min, solvent was evaporated in vacuo. An attempt to re-crystallization of the solid residue from CH 3 CN led to formation of the powder Se which was separated by filtration of hot solution. The filtrate was concentrated in vacuo. The solid was re-crystallized from CH 3 CN to give I as yellow

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.95 Å and refined in the riding model with fixed isotropic displacement parameters [U iso (H) = 1.2U eq (C)].

Figure 2
The molecular structure of I showing the atomic numbering and 50% probability displacement ellipsoids.

[Bis(pyridin-2-yl) selenide-κ 2 N,N′]tetrachloridotin(IV)
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.