Crystal structure of poly[di-μ-aqua-{5-[(1Z)-2-(4-chlorophenyl)-1-cyanoethenyl]-1,2,3,4-tetrazol-1-ido-κN 1}sodium]

In the title compound, [Na(C10H5ClN5)(H2O)2]n, infinite chains of [Na(H2O)2]+ cations having a diamond-shaped cross-section and running parallel to the b axis are formed. O—H⋯N hydrogen bonds to the anions generate layers parallel to (100) which have the chlorobenzenecyanoethenyl substituents protruding from both surfaces. The sodium ion makes a short contact of 2.4801 (13) Å with the N atom of the tetrazolide ring which is syn to the cyano N atom.


S1. Comment
Tetrazole compounds have been largely associated with a wide range of applications in medicine, biochemistry and agriculture (Modarresi et al., 2009;Singh et al., 1980). The medicinal activity of the tetrazole functionality is due to its ability to serve as a bioequivalent (bioisostere) of the carboxylic acid group (Smith et al., 1991;Duncia et al., 1990).
They are also used as anti-hypertensive, anti-allergic, anti-biotic and anti-convulsant agents (Myznikov et al., 2007;Schocken et al., 1989;Mekni & Bakloiti, 2008;Lim et al., 2007). As part of our on-going study of bio-active molecules we herein report the synthesis and X-ray structure of the title compound as a building block precursor in the synthesis of new tetrazole scaffold compounds.
The title compound, Fig (Table 1) to generate layers parallel to (100) which have the chlorobenzenecyanoethenyl substituents protruding from both surfaces (Figs 3 and 4). Additionally, the sodium ion makes a contact of 2.4801 (13) Å with N4 of the tetrazolide ring which is significantly shorter than the sum of the ionic radius of Na + and the van der Waals radius of N (2.71 Å). The C-N and N-N bond lengths in the ring (1.314 (2)-1.345 (2) Å) suggest significant delocalization of the negative charge. The hydrogen bonding interactions may restrict the cation to approach this site as opposed to the face of the ring. The tetrazolide and benzene rings, respectively, make dihedral angle of 4.8 (2) and 25.8 (2)° with the plane defined by C2-C4.

S2. Experimental
The title compound has been obtained as an unexpected product from a multi-component reaction of 1 mmol (94 mg) of amino-pyridine, 4-chloro-benzaldehyde (1 mmol, 141.5 mg), malononitrile (1 mmol, 66 mg), sodium acetate (0.15 mmol, 12.3 mg) and sodium azide (1 mmol, 65 mg). The reaction mixture was refluxed in ethanol/water (1:1) and monitored by TLC until completion after 3 hours. On cooling, the solid precipitate was collected, dried under vacuum and recrystallized from ethanol to afford suitable crystals for X-ray diffraction. Title compound with numbering scheme and 50% probability ellipsoids.

Figure 3
Packing viewed along the b axis.

Figure 4
Elevation view of the chain structure.

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. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 Å) while those attached to oxygen were placed in locations derived from a difference map and their parameters adjusted to give O-H = 0.84 Å. All were included as riding contributions with isotropic displacement parameters 1.2 times those of the attached atoms.