catena-Poly[[[bis(acetato-κ2 O,O′)aquacadmium]-μ-[(pyridin-3-yl)(pyridin-4-yl)methanone]-κ2 N:N′] dihydrate]

In the title complex, {[Cd(CH3COO)2(C11H8N2O)(H2O)]·2H2O}n, the CdII ion adopts an O5N2 pentagonal–bipyramidal coordination geometry with four acetate O atoms and one water O atom at the equatorial sites and two pyridine N atoms at the axial sites. The (pyridin-3-yl)(pyridin-4-yl)methanone ligand acts in a μ2-bridging mode, linking the metal atoms, leading to an infinite chain along [-110]. O—H⋯O hydrogen bonds involving the lattice water molecules connect these chains into a three-dimensional network.


Experimental
The ligand was prepared according to the procedure of the literature reported (Chen & Mak 2005). The Cd(CH 3 CO 2 ) 2 .2H 2 O (30 mg, 0.12 mmol) and 3-pyridinyl-4-pyridinylmethanone (19 mg, 0.1 mmol) were dissolved in a mixed solvent of 1 ml deionized water and 3 ml acetonitrile with stirring at room temperature. After 3 hours, the resulted clear solution was filtered and the filtrate was left to stand in air. The clolorless crystals suitable for x-ray diffraction analysis were deposited after about two weaks (23.9 mg, 52% yield).

Refinement
All the H atoms were located in the difference electron density maps but were placed in idealized positions and allowed respectively, and U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (C methyl , O).

Figure 1
The title complex showing the atom-numbering scheme, with displacement ellipsoids shown at the 30% probability level.
All aryl hydrogen atoms are omitted for clarity. Symmetry codes: (i) x -1, y + 1, z.  The hydrogen-bonding interactions that assemble with the infinite chain structures. The red-dashed lines represent hydrogen-bonding interactions. All water O atoms were shown as red balls, and all aryl H atoms are omitted for clarity. 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.

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