catena-Poly[[tetraaquacadmium]-μ-5,5′-(1,4-phenylene)di(tetrazol-2-ido)-κ2 N 2:N 2′]

In the title compound, [Cd(C8H4N8)(H2O)4]n, 5,5′-(1,4-phenylene)di(tetrazol-2-ide) (L) ligands bridge CdII atoms into polymeric chains along [201]. The CdII atom is situated on an inversion centre and is coordinated by two N atoms from two L ligands and by four water O atoms in a distorted octahedral geometry. In the L ligand, the benzene ring resides on an inversion centre and the tetrazole rings are twisted from its plane by 22.3 (1)°. An extensive hydrogen-bonding network formed by classical O—H⋯N and O—H⋯O interactions consolidates the crystal packing, linking the poymeric chains into a three-dimensional structure.

In the title compound, [Cd(C 8 H 4 N 8 )(H 2 O) 4 ] n , 5,5 0 -(1,4phenylene)di(tetrazol-2-ide) (L) ligands bridge Cd II atoms into polymeric chains along [201]. The Cd II atom is situated on an inversion centre and is coordinated by two N atoms from two L ligands and by four water O atoms in a distorted octahedral geometry. In the L ligand, the benzene ring resides on an inversion centre and the tetrazole rings are twisted from its plane by 22.3 (1) . An extensive hydrogen-bonding network formed by classical O-HÁ Á ÁN and O-HÁ Á ÁO interactions consolidates the crystal packing, linking the poymeric chains into a three-dimensional structure.
In the title compound ( Fig. 1), the Cd II ion is located at an inversion centre. It has a slightly distorted octahedral coordination geometry formed by four water molecules and two nitrogen atoms from ligands L, where H 2 L = 1,4-bis-(tetrazol-5-yl)benzene. Four oxygen atoms form a planar parallelogram arrangement around the Cd centre, and the other two nitrogen atoms occupy the apical position. Each ligand L coordinates two cadmium atoms in a µ 2 -bridging mode, thus generating a one-dimension coordination polymer. As far as we known, this coordination mode is currently unknown for L ligand.
In the crystal, polymeric one-dimensional chains are linked via O-H···N hydrogen bonds (Table 1) into a threedimensional structure. The results show that there are no channels in the crystal structure.

Experimental
Cadmium nitrate tetrahydrate (0.123 g, 0.40 mmol), 1,4-bis(tetrazole-5-yl)benzene (0.042 g, 0.20 mmol) and sodium hydroxide (0.016, 0.40 mmol) were added to 8 ml of water:ammonium hydroxide (v:v=1:1) mixture. The solution was transferred into a Teflon-lined stainless steel autoclave and the autoclave was heated to 393 K and maintained at that temperature for 72 h. After cooling to room temperature, crystals suitable for X-ray diffraction were collected.

Refinement
Water hydrogen atoms were placed in calculated positions [O-H = 0.85-0.87 Å], and refined as riding, with U iso (H) = 1.5 U eq (O). The aromatic H atoms were positioned geometrically [C-H = 0.93 Å], and refined using a riding model, with U iso (H) = 1.2 U eq (C).

catena-Poly[[tetraaquacadmium]-µ-5,5′-(1,4-phenylene)di(tetrazol-2-ido)-κ 2 N 2 :N 2′ ]
Crystal data 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.