catena-Poly[aquabis(μ-3-chlorobenzoato-κ2 O:O′)zinc]

In the polymeric title compound, [Zn(C7H4ClO2)2(H2O)]n, the ZnII cation is located on a twofold rotation axis and is coordinated by carboxylate O atoms of four monodentate chlorobenzoate anions and by one water molecule, located on a twofold rotation axis, in a distorted square-pyramidal geometry. In the anion, the carboxylate group is twisted away from the attached benzene ring by 44.16 (11)°. The chlorobenzoate anion bridges ZnII cations, forming polymeric chains running along the c-axis direction. O—H⋯O hydrogen bonds between coordinating water molecules and carboxylate groups link adjacent chains into layers parallel to the bc plane.

In the polymeric title compound, [Zn(C 7 H 4 ClO 2 ) 2 (H 2 O)] n , the Zn II cation is located on a twofold rotation axis and is coordinated by carboxylate O atoms of four monodentate chlorobenzoate anions and by one water molecule, located on a twofold rotation axis, in a distorted square-pyramidal geometry. In the anion, the carboxylate group is twisted away from the attached benzene ring by 44.16 (11) . The chlorobenzoate anion bridges Zn II cations, forming polymeric chains running along the c-axis direction. O-HÁ Á ÁO hydrogen bonds between coordinating water molecules and carboxylate groups link adjacent chains into layers parallel to the bc plane.

Comment
The structural functions and coordination relationships of the arylcarboxylate ion in transition metal complexes of benzoic acid derivatives change depending on the nature and position of the substituent groups on the benzene ring, the nature of the additional ligand molecule or solvent, and the medium of the synthesis . Transition metal complexes with biochemically active ligands frequently show interesting physical and/or chemical properties, as a result they may find applications in biological systems (Antolini et al., 1982). Some benzoic acid derivatives, such as 4-aminobenzoic acid, have been extensively reported in coordination chemistry, as bifunctional organic ligands, due to the varieties of their coordination modes (Chen & Chen, 2002;Amiraslanov et al., 1979;Hauptmann et al., 2000). The title compound was synthesized and its crystal structure is reported herein.
The asymmetric unit of the title compound, (I), contains one-half Zn II cation, one chlorobenzoate (CB) anion and onehalf water molecule (Fig. 1). In the crystal, two CB anions bridge adjacent Zn II cations, forming a polymeric chain running along the c axis, while the water molecule coordinate in a monodentate manner to the Zn II cation, completing the distorted square-pyramidal geometry (Fig. 2). As a result of the CB anions bridging of the adjacent Zn II cations, an eightmembered ring is formed where the distances between the symmetry related atoms, Zn1···Zn1b    (Zaman et al., 2012) and [Co(C 7 H 4 IO 2 ) 2 (H 2 O) 2 ] n (Aydın et al., 2012) have also been reported.
In the crystal, strong O-H···O hydrogen bonds (Table 2) link the water hydrogens to the carboxylate oxygens in the polymeric chains (Fig. 3).

Experimental
The title compound was prepared by the reaction of ZnSO 4 .H 2 O (0.89 g, 5 mmol) in H 2 O (50 ml) with sodium 3-chlorobenzoate (1.79 g, 10 mmol) in H 2 O (100 ml) at room temperature. The mixture was filtered and set aside to crystallize at ambient temperature for one week, giving colorless single crystals.

Refinement
Atom H31 (for H 2 O) was located in a difference Fourier map and was refined freely. The C-bound H-atoms were positioned geometrically with C-H = 0.93 Å for aromatic H-atoms, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C).

Figure 1
The asymmetric unit of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

catena-Poly[aquabis(µ-3-chlorobenzoato-κ 2 O:O′)zinc]
Crystal data 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 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.  (10) 0.0049 (7) 0.0062 (7) −0.0030 (7) Geometric parameters (Å, º)