Diaquabis(2,2′-biimidazole)cobalt(II) dichloride

There are independent cations and four chloride anions in the crystal structure of the title complex, [Co(C6H6N4)2(H2O)2]Cl2. In each cation, the CoII cation is coordinated by four N atoms from two biimidazole and two O atoms of two water molecules; one Co atom is at a position of site symmetry m, the other at a position of site symmetry 2/m. All Cl− ions and water molecules are also located on the mirror plane. Each structural unit is connected through O—H⋯Cl and N—H⋯Cl intermolecular hydrogen bonds, forming a three–dimensional supramolecular structure.

There are independent cations and four chloride anions in the crystal structure of the title complex, [Co(C 6 H 6 N 4 ) 2 -(H 2 O) 2 ]Cl 2 . In each cation, the Co II cation is coordinated by four N atoms from two biimidazole and two O atoms of two water molecules; one Co atom is at a position of site symmetry m, the other at a position of site symmetry 2/m. All Cl À ions and water molecules are also located on the mirror plane. Each structural unit is connected through O-HÁ Á ÁCl and N-HÁ Á ÁCl intermolecular hydrogen bonds, forming a threedimensional supramolecular structure.

Comment
The imidazole coordinated complexes have various structures and extensive uses in the field of catalysis, materials and bioactivity (Barquin et al., 2003;Hirotoshi & Eisaku, 2005). The bis(2,2'-biimidazole)dihydrate cobalt dichloride was synthesized. The 2,2'-biimidazole is an interesting dicyclo-ligand of containing four N atoms: the two N atoms forming coordinate bonds and the other two -uncoordinated N atoms of biimidazole form N-H···Cl hydrogen bonds. This crystal structure are constructed by intermolecular hydrogen bonds (Tadokoro & Nakasuji, 2000;Roth et al., 2000).
The average bond distance Co-N is of 2.1563 (18)

Experimental
The 2,2'-biimidazole was prepared according to (Fieselmann et al., 1978). 2,2'-Biimidazole (0.1 mmol) was mixed with 0.1 mmol CoCl 2 . 6H 2 O in solution. After 10 min of stirring, the precipitate was filtered off, the resulting clear solution was allowed to stand at room temperature, after a few days yellow block-shaped crystals were obtained.

Refinement
H atoms of water molecules are located in a difference map and refined with distance restraints of O-H = 0.86 (1) Å. Fig. 1. The molecular structure of the title complex with the atom labeling scheme. Displacement ellipsoids are drawn at 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Special details
Geometry. All s.u.'s (except the s.u.'s in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.