Diaquabis(tetrazolo[1,5-a]pyridine-8-carboxylato-κ2 N 1,O)cobalt(II) dihydrate

In the title compound, [Co(C6H3N4O2)2(H2O)2]·2H2O, the CoII atom is located on an inversion center in a slightly distorted octahedral environment formed by the O atoms of two water molecules, and the N and O atoms of the chelating tetrazolo[1,5-a]pyridine-8-carboxylate anions. Hydrogen bonds of the O—H⋯O and O—H⋯N types result in a three-dimensional supramolecular network.

In the title compound, [Co(C 6 H 3 N 4 O 2 ) 2 (H 2 O) 2 ]Á2H 2 O, the Co II atom is located on an inversion center in a slightly distorted octahedral environment formed by the O atoms of two water molecules, and the N and O atoms of the chelating tetrazolo[1,5-a]pyridine-8-carboxylate anions. Hydrogen bonds of the O-HÁ Á ÁO and O-HÁ Á ÁN types result in a three-dimensional supramolecular network.

Related literature
For background to coordination compounds and their synthesis by in situ reaction, see: Chen & Tong (2007); Liu et al. (2005); Li et al. (2007).

Comment
Coordination complexes have attracted great attention in recent years. (Liu,et al., 2005). The in-situ reaction which can create new ligand and structure draw much more attention in synthesizing coordination complexes (Li,et al., 2007). Some interesting complexes were ganied by the in-situ reaction. (Chen,et al., 2007).
In the title compound, the cobalt atom the cobalt atom located in the inverse center is six coordinated by two waters and two tetrazolo(1,5-a)pyridine-8-carboxylato, (Fig. 1). Each tetrazolo(1,5-a)pyridine-8-carboxylato chelates to one cobalt atom. One type of water coordinates to the cobalt and the other acts as lattice water. A three dimensional supramolecular net formed by the hydrogen bonds of waters and tetrazolo(1,5-a)pyridine-8-carboxylato ligands intermolecular (Fig. 2).

Experimental
A mixture of cobalt(II)nitrate and sodium azide (1 mmol), 2-chloronicotinic acid(0.5 mmol), in 10 ml of water was sealed in a Teflon-lined stainless-steel Parr bomb that was heated at 363 K for 48 h. Red crystals of the title complex were collected after the bomb was allowed to cool to room temperature.Yield 20% based on cobalt(II). Caution: Azides may be explosive.
Although we have met no problems in this work, only a small amount of them should be prepared and handled with great caution.

Refinement
Hydrogen atoms were included in calculated positions and treated as riding on their parent C atoms with C-H = 0.93Å and U iso (H) = 1.2U eq (C).Hydrogen atom of water were added by difference Fourier maps and refined with restrainated distance of O-H = 0.85Å with a error of 0.02Å, and the restrainated distance of H-H = 1.35Å with a error of 0.01Å of the same water.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq