Dichloridobis(3-chloropyridine-κN)zinc

In the crystal structure of the title compound, [ZnCl2(C5H4ClN)2], discrete complex molecules are found in which the ZnII cations are coordinated by two chloride anions and the N atoms of the two 3-chloropyridine ligands within a slightly distorted tetrahedron. Moreover, intermolecular C—Cl⋯Cl—C halogen interactions (Cl⋯Cl = 3.442 Å) are found between the building blocks.


Comment
Halogen interactions as one weak noncovalent interaction, is of importance in e.g. crystal engineering and molecular recognition processes (Metrangolo & Resnati, 2001). Such interactions are widely found in various organometallic coordination compounds like e.g. in coordination compounds built up on multidentate ligands with pyridine groups which generate networks with a variety of special functions ( Leininger et al., 2000 andBertani et al., 2010).
As a part of our project on halogen halogen interactions the tile compound was prepared and characterized by single crystal X-ray diffraction. In the crystal structure of the title compound discrete complexes are found in which each zinc(II) cation is coordinated by two 3-chloropyridine ligands and two chloride anions. The coordination environment around the Zn cations consists of slightly distorted tetrahedra, which is typical for such complexes ( Bhosekar et al., 2008;Wriedt et al., 2009). The crystal structure is characterized by intermolecular C-Cl···Cl-C interactions with Cl···Cl separations less than the sum of Van der Waals radii (Lommerse, et al., 1996).

Experimental
Zinc(II) chloride (1 mmol) dissolved in 10 mL of ethanol, was added dropwise to a stirred solution of 3-chloropyridine (1 mmol) in 10 mL of ethanol. Subsequently, the mixture was refluxed for 2 h, and the resulting solution was further concentrated by the rotary evaporation at 40 Celsius degree. Finally, the concentrated solution was left to slowly evaporate at room temperature until the crystal formed.

Refinement
All H atoms were placed in calculated positions and allowed to ride on their parent atoms at distances of 0.93Å with isotropic displacement parameters 1.2 times Ueq of the parent atoms. Fig. 1. Crystal structure of the title compound with labeling and displacement elliposids drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds supplementary materials sup-3 in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(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.