2-(2H-Tetrazol-5-yl)pyridinium chloride

In the title compound, C6H6N5 +·Cl−, the pyridinium and tetrazole rings are essentially coplanar. The pyridine N atoms are protonated. In the crystal structure, molecules are connected via N—H⋯Cl, C—H⋯Cl, C—H⋯N and N—H⋯N hydrogen bonds into layers that are parallel to the (001) plane. There are two crystallographically independent molecules in the asymmetric unit which are located on mirror planes.

In the title compound, C 6 H 6 N 5 + ÁCl À , the pyridinium and tetrazole rings are essentially coplanar. The pyridine N atoms are protonated. In the crystal structure, molecules are connected via N-HÁ Á ÁCl, C-HÁ Á ÁCl, C-HÁ Á ÁN and N-HÁ Á ÁN hydrogen bonds into layers that are parallel to the (001) plane. There are two crystallographically independent molecules in the asymmetric unit which are located on mirror planes.

S1. Comment
Tetrazole derivatives have found wide range of applications in coordination chemistry because of their multiple coordination modes as ligands to metal ions and for the construction of novel metal-organic frameworks (Wang et al., 2005;Xiong et al., 2002;Wen, 2008). In our ongoing investigations in this field we report here the crystal of 2-(2Htetrazol-5-yl)pyridine-1-ium chloride (Fig.1).
In the crystal structure there are two crystallographically independent molecules, both of them located on mirror planes. Therefore, the benzene and tetrazole rings in both independent molecules are essentially planar. The geometric parameters of the tetrazole rings are comparable to those in related molecules (Wang et al., 2005;Dai & Fu, 2008).
The crystal structure is stabilized by N-H···Cl, C-H···Cl, C-H···N and N-H···N hydrogen bonding. The different H bonding interactions connect the molecules into layers, that are parallel to the (0 0 1) plane (Table 1, Fig. 2).

S2. Experimental
Picolinonitrile (30 mmol), NaN 3 (45 mmol), NH 4 Cl (33 mmol) and DMF (50 ml) were added in a flask under nitrogen atmosphere and the mixture stirred at 110°C for 20 h. The resulting solution was then poured into ice-water (100 ml), and a white solid was obtained after adding HCl (6 M) till pH=6. The precipitate was filtered and washed with distilled water.
Colourless block-shaped crystals suitable for X-ray analysis were obtained from the crude product by slow evaporation of the solvent from an ethanol/HCl (50:1 v/v) solution.

S3. Refinement
All H atoms were located in difference map but were positioned with idealized geometry with C-H = 0.93 Å and N-H = 0.86 Å and were refined isotropic with U iso (H) = 1.2Ueq(C or N) using a riding model.   The crystal packing of the title compound viewed along the c axis showing the two-dimensionnal hydrogen bondings network. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.32 e Å −3 Δρ min = −0.23 e Å −3

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.