Bis[5-(2-amino-3-pyridyl)tetrazolato]copper(II)

In the centrosymmetric title complex, [Cu(C6H5N6)2], the CuII ion is coordinated by four N atoms from two symmetry-related bidentate 5-(2-amino-3-pyridyl)tetrazolate ligands in a slightly distorted square-planar environment. There are weak intramolecular N—H⋯N hydrogen bonds between the two ligands. In the crystal structure, there are significant π–π stacking interactions between symmetry-related tetrazole and pyridine rings, with a centroid–centroid distance of 3.6025 (18)°.

In the centrosymmetric title complex, [Cu(C 6 H 5 N 6 ) 2 ], the Cu II ion is coordinated by four N atoms from two symmetry-related bidentate 5-(2-amino-3-pyridyl)tetrazolate ligands in a slightly distorted square-planar environment. There are weak intramolecular N-HÁ Á ÁN hydrogen bonds between the two ligands. In the crystal structure, there are significantstacking interactions between symmetry-related tetrazole and pyridine rings, with a centroid-centroid distance of 3.6025 (18) .

Comment
In situ [2+3] cycloaddition synthesis of tetrazole coordination polymers under hydrothermal conditions has proved to be a fast and convenient route to explore novel coordination polymers with rich structural diversities and potential physical properties, such as second harmonic generation (SGH), ferroelectric and dielectric responses (Xiong et al., 2002;Ye et al., 2006;Fu et al. (2008). The crystal structure of the compound formed by our hydrothermal synthesis is reported herein.
The molecular structure of the title compound is shown in Fig. 1. The Cu II ion lies on an inversion center coordinated by four N atoms from two symmetry related bidentate 3-(2-Amino-pyridyl))tetrazolato ligands in a slightly distorted squareplanar environment. In the crystal structure, there are significant π-π stacking interactions between symmetry related tetrazole and pyridine rings with a centroid to centroid distance of 3.6025 (18)°.

Experimental
The title compound was prepared by hydrothermal treatment of 2-aminonicotinonitrile (2.3 mmol) and Cu(NO 3 ) 2 (1.0 mmol) with excess amount of NaN 3 in a sealed Pyrex tuble at 403K for 2-4 days. The resulting green rectangular crystals gave a yield of 75% based on Cu(NO 3 ) 2 .

Refinement
H atoms were placed in caculated positions with C-H = 0.93 and N-H = 0.90Å and refined using a riding-model approximation with U iso (H) = 1.2U eq (C,N). Fig. 1. The molecular structure of the title compound with the atomic numbering scheme. Displacement ellipsoids were drawn at the 30% probability level. Symmetry code: (a) -x+1, -y+1, -z+1. Hydrogen bonds are shown as dashed lines.

Bis[5-(2-amino-3-pyridyl)tetrazolato]copper(II)
Crystal data [Cu(C 6  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 Rfactors(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.