catena-Poly[[aquacadmium(II)]-bis(μ2-4-chlorobenzoato)]

In the title complex, [Cd(C7H4ClO2)2(H2O)]n, the Cd atom lies on a twofold axis and adopts a square-pyramidal coordination geometry. The water molecule occupies the axial site with O atoms from four different 4-chlorobenzoato ligands in the equatorial plane. Pairs of 4-chlorobenzoato ligands bridge adjacent CdII ions, generating an infinite chain structure along the c axis. Parallel polymeric chains are further interconnected through water–acetate O—H⋯O hydrogen bonds, forming layers in the bc plane.

In the title complex, [Cd(C 7 H 4 ClO 2 ) 2 (H 2 O)] n , the Cd atom lies on a twofold axis and adopts a square-pyramidal coordination geometry. The water molecule occupies the axial site with O atoms from four different 4-chlorobenzoato ligands in the equatorial plane. Pairs of 4-chlorobenzoato ligands bridge adjacent Cd II ions, generating an infinite chain structure along the c axis. Parallel polymeric chains are further interconnected through water-acetate O-HÁ Á ÁO hydrogen bonds, forming layers in the bc plane.

Comment
Organic acids are widely used as versatile building blocks in many metal-organic frameworks with diverse structural motifs (Zhao et al., 2003;Cao et al., 2002;Zhang et al., 2004). In metal complexes the 4-chlorobenzoato anion can function both to balance charge and as a bridging ligand. Several structures incorporating this ligand have been investigated (Turpeinen, et al., 1999;Xue et al., 2006 (Rodesiler et al., 1985).
Experimental 4-chlorobenzoic acid (0.040 g, 0.3 mmol) was dissolved in a mixture of methanol, 2 ml, and acetonitrile, 2 ml. Sodium hydroxide was subsequently added at room temperature to adjust the pH to 7. Then, Cd(ClO 4 ) 2 .6H 2 O (0.371 g, 0.1 mmol) was added and the solution stirred for an hour. The clear solution was filtered and then left to stand in air. After 6 days colorless rod-like crystals were deposited (260 mg, 72% yield).

Refinement
The hydrogen

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^ > 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 )