catena-Poly[[bis(pyridine-3-carboxylic acid-κN)mercury(II)]-di-μ-chlorido]

In the title compound, [HgCl2(C6H5NO2)2]n, the HgII cation is located on an inversion center and is six-coordinated in a distorted octahedral geometry by two N atoms from two pyridine-3-carboxylic acid molecules and four bridging Cl− anions. The bridging function of the Cl− anions leads to polymeric chains running along the a axis. One Hg—Cl bond is much longer than the other. In the crystal, O—H⋯O and weak C—H⋯Cl hydrogen bonds are observed.

In the title compound, [HgCl 2 (C 6 H 5 NO 2 ) 2 ] n , the Hg II cation is located on an inversion center and is six-coordinated in a distorted octahedral geometry by two N atoms from two pyridine-3-carboxylic acid molecules and four bridging Cl À anions. The bridging function of the Cl À anions leads to polymeric chains running along the a axis. One Hg-Cl bond is much longer than the other. In the crystal, O-HÁ Á ÁO and weak C-HÁ Á ÁCl hydrogen bonds are observed.
The asymmetric unit of the title compound, (Fig. 1), contains one half -molecule. The Hg II atom is six-coordinated in a distorted octahedral configuration by two N atoms from two 3-pyridine carboxylic acid and four bridging Cl. The bridging function of the chloro atoms leads to a one-dimensional chain structure. The Hg-Cl and Hg-N bond lengths and angles are collected in Table 1. In the crystal structure, intermolecular O-H···O and C-H···Cl hydrogen bonds (Table 2, Fig. 2) may stabilize the structure.

Experimental
A solution of pyridine-3-carboxylic acid (0.25 g, 2.0 mmol) in methanol (20 ml) was added to a solution of HgCl 2 (0.27 g, 1.0 mmol) in methanol (20 ml) and the resulting colorless solution was stirred for 15 min at room temperature. This solution was left to evaporate slowly at room temperature. After one week, colorless needle crystals of the title compound were isolated (yield 0.41 g, 79.2%).

Refinement
H atoms were positioned geometrically, with C-H = 0.93 Å and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C).

catena-Poly[[bis(pyridine-3-carboxylic acid-κN)mercury(II)]-di-µ-chlorido]
Crystal data [HgCl 2 (C 6 H 5 NO 2 ) 2 ] M r = 517.71 Triclinic, P1 Hall symbol: -P 1 a = 3.8298 (5) Å b = 6.5626 (9) Å c = 14.5831 (18)  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 )