Poly[aqua(μ2-pyrimidine-2-carboxylato-κ4 O,N:O′,N′)(nitrato-κO)cadmium]

In the title polymer, [Cd(C5H3N2O2)(NO3)(H2O)]n, the CdII atom is seven-coordinate in a distorted capped octahedral geometry by two N atoms of two different pyrimidine dicarboxylate (pmc) ligands, three O atoms from three separate pmc ligands, and two O atoms of disordered nitrate anions or water molecules. The CdII atoms are bridged by the pmc ligands in a chelating/bridging bis-bidentate and chelating bidentate mode, forming sheets parallel to (20-1). The sheets are further linked into a three-dimensional supramolecular network via classical O—H⋯O hydrogen bonds involving the nitrate anions and coordinating water molecules. Intramolecular O—H⋯O hydrogen bonding is also observed. The non-coordinating nitrate O atoms are disordered over two sets of sites with occupancies of 0.57 (7) and 0.43 (7).

In the title polymer, [Cd(C 5 H 3 N 2 O 2 )(NO 3 )(H 2 O)] n , the Cd II atom is seven-coordinate in a distorted capped octahedral geometry by two N atoms of two different pyrimidine dicarboxylate (pmc) ligands, three O atoms from three separate pmc ligands, and two O atoms of disordered nitrate anions or water molecules. The Cd II atoms are bridged by the pmc ligands in a chelating/bridging bis-bidentate and chelating bidentate mode, forming sheets parallel to (201). The sheets are further linked into a three-dimensional supramolecular network via classical O-HÁ Á ÁO hydrogen bonds involving the nitrate anions and coordinating water molecules. Intramolecular O-HÁ Á ÁO hydrogen bonding is also observed. The non-coordinating nitrate O atoms are disordered over two sets of sites with occupancies of 0.57 (7) and 0.43 (7).
The immediate coordination environment about the cadmium atom in I is shown in Fig. 1 revealing that the Cd(II) atom is heptacoordinate in a distorted capped octahedral geometry constructed by two N and two O atoms from two different pcm ligands, one O atom from a third pcm ligand, and two O atoms of disordered nitrate anions or water molecules. The Cd-N and Cd-O bond distances (Table 1) agree with those found in other N,O-chelate Cd(II) complexes (Sava et al., 2008;Zhang et al., 2008). Each Cd(II) is connected to four other Cd atoms through three pmc ligands generating two dimensional sheets parallel to (201), Fig. 2. Within the sheets, the Cd···Cd distances through the µ 2 -carboxylate bridge and the Cd···Cd distances across the pmc ligands are 3.9714 (4) and 6.2427 (3) Å, respectively. The sheets are stabilized by inversion-related pairs of intermolecular O-H···O hydrogen bonds between the coordinated water and nitrate molecules ( Table 2). There are, however, no π-π interactions between adjacent pyrimidine rings within the sheets. The distance between C g to C g of the pyrimidine rings of the pmc ligands is 4.114 (3) Å, which is out the range (3.3-3.8 Å) considered for significant π-π interactions (Janiak, 2000). Further intermolecular O-H···O hydrogen bonds involving the nitrate anions and coordinated water molecules (Table 2)

Refinement
The carbon-bound hydrogen atoms were placed in geometrically idealized positions and constrained to ride on their parent atom positions with C-H distances of 0.93 Å and with U iso (H) = 1.2U eq (C) for the aromatic H atoms. The hydrogen atoms attached to oxygen atoms of the water molecules were located in a difference Fourier map and refined as riding in their as-found positions with a DFIX restraint of O-H distance at 0.900±0.001 Å, with U iso (H) = 1.2U eq (O). The nitrate anion was shown to be disordered over two sites in a 0.57 (7) and 0.43 (7)  program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia,1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figure 1
Displacement ellipsoid plot at the 35% probability level of the immediate coordination geometry about the cadmium(II) centre in I. The asymmetric unit is labelled.

Poly[aqua(µ 2 -pyrimidine-2-carboxylato-κ 4 O,N: O′,N′)(nitrato-κO)cadmium]
Crystal data 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 Occ. (