Poly[bis[μ3-2-(1H-tetrazol-1-yl)acetato]cadmium(II)]

In the title compound, [Cd(C3H3N4O2)2]n, the CdII ion, located on a twofold rotation axis, is six-coordinated by two N atoms [Cd—N = 2.368 (2) Å] and four O atoms [Cd—O = 2.300 (1) and 2.260 (1) Å] from six 2-(1H-tetrazol-1-yl)acetate (L) ligands in a distorted octahedral geometry. The metal centres are connected via the tridentate L ligands into a three-dimensional polymeric structure.


Experimental
Crystal data [Cd(C 3

Poly[bis[µ 3 -2-(1H-tetrazol-1-yl)acetato]cadmium(II)]
Li-Xia Xie, Xian-Fu Zheng, Hui Su and Qiu Jin S1. Comment Multidentate ligands containing rich coordination sites (N and/or O donors) are often employed to produce polymeric networks with structural diversity owing to their various coordination modes (Won et al., 2007;Lee et al., 2005;Du et al., 2007). As ligands with multiple coordination site, tetrazole and its derivatives have been shown to be good organic linker in generation of structurally versatile metal-organic frameworks since it can bridge different metal centers to afford coordination polymers that exhibit extraordinary structural diversity and facile accessibility of functionalized materials (Yang et al., 2009). Here, we report the synthesis and crystal structure of the title compound, (I).
In (I) (Fig. 1), each Cd II ion located on a twofold rotation axis is six-coordinated by two tetrazole nitrogen atoms (N4) and four carboxylate group oxygen atoms (O1 and O2) from six distinct ligands. The coordination bond lengths Cd-N and Cd-O are 2.368 (2), 2.300 (1) Å and 2.260 (1) Å, respectively. The coordination geometry around Cd II can be described as a distorted octahedron -the Cd II coordination angles are in the range 83.34 (6)° -177.16 (7)°. Each fully deprotonated L ligand serves as a tridentate bridging ligand via one nitrogen atom at the 5-position of the tetrazole ring while the nitrogen atoms at 3,4-positions remain uncoordinated, and two carboxylate O atoms. In this way two metal atoms and two carboxylate form a 8-membered [M 2 C 2 O 4 ] metallocyclic ring, the Cd···Cd distance is 4.793 Å. The Cd···Cd distance linked by the bridged L ligand is 8.603 Å. Thus each Cd II centers are linked together by six L ligands into a three-dimensional polymeric structure (Fig. 2).

S2. Experimental
All solvents and chemicals were of analytical grade and were used without further purification. The compound [CdL 2 ] n was synthesized as follows: 2-(1H-tetrazol-1-yl) acetic acid (1.0 mmol) was added to 5 cm 3 water and the resulting solution was adjusted pH to 7.0 by NaOH aqueous. Then Cd(NO 3 ) 2 (0.5 mmol) was added to the above solution, and the mixture was stirred for 30 min and filtered. After two days, colourless single crystals suitable for X-ray analysis were obtained. Anal. Calcd (%) for C 6

Figure 2
The crystal packing viewed along the b axis. H atoms omitted for clarity.

Poly[bis[µ 3 -2-(1H-tetrazol-1-yl)acetato]cadmium(II)]
Crystal data Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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.