catena-Poly[[dichloridomercury(II)]-μ-{N-[(E)-pyridin-2-ylmethylidene-κN]pyridin-3-amine-κ2 N 1:N 3}]

In the title coordination polymer, [HgCl2(C11H9N3)]n, the HgII ion is coordinated by three N atoms from two N-[(E)-pyridin-2-ylmethylidene]pyridin-3-amine (L) ligands and two chloride anions in a distorted trigonal–bipyramidal geometry. The two pyridine rings in L form a dihedral angle of 50.0 (2)°. L ligands bridge adjacent HgCl2 units into polymeric chains propagating in [010]. The crystal packing is further stabilized by weak intermolecular C—H⋯Cl hydrogen bonds and π–π interactions between the pyridine rings, with a centroid–centroid separation of 3.529 (9) Å.


Related literature
For related structures and applications of coordination polymers, see: Moulton & Zaworotko (2001); Fei et al. (2000). For the synthesis of the ligand and the index of trigonality, see: Dehghanpour et al. (2012).
The asymmetric unit of the title polymeric complex, consisting of one Hg(II) ion, one PyPy ligand and two chloride anions, is shown in Fig. 1. The coordination geometry around Hg(II) is a distorted trigonal-bipyramidal geometry, with the Hg (II) ion being surrounded by two Cl, two N atoms from one PyPy ligand and one N atom from adjacent PyPy ligand. The structural index τ, (Dehghanpour et al., 2012) which is a measure of trigonal distortion, is 0.59 for the title structure indicating a distorted trigonal-bipyramidal environment of Hg(II).
These chains interact via π-π interactions between adjacent pyridine ringe (N3/C7-C11) related by inversion center, and the distance between their centroids is equal to 3.529 (9) Å. The C-H···Cl interactions (Table 1) are also observed in the crystal structure.

Experimental
The title complex was prepared by the reaction of HgCl 2 (27.1 mg, 0.1 mmol) and pyridin-3-ylpyridin-2-ylmethyleneamine (18.3 mg, 0.1 mmol) in 25 ml of acetonitrile at room temperature. The solution was allowed to stand at room temperature and yellow crystals of the title compound suitable for X-ray analysis precipitated within few days.

Refinement
H atoms were placed in calculated positions with C-H = 0.95 Å, and included in the refinement in a riding-motion approximation, with U iso (H)= 1.2U eq (C).

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq