Tetraimidazolebis(trichloroacetato)copper(II)

The title compound, [Cu(C2Cl3O2)2(C3H4N2)4], was prepared by the reaction of imidazole and trichloroacetatocopper(II). The CuII atom adopts a distorted octahedral coordination geometry, binding the N atoms of four imidazole ligands and the carboxylate O atoms of two trichloroacetate anions. The molecular structure and packing are stabilized by N—H⋯O hydrogen-bonding interactions. Close intermolecular Cl⋯Cl contacts [3.498 (3) Å] are also found in the structure.

The title compound, [Cu(C 2 Cl 3 O 2 ) 2 (C 3 H 4 N 2 ) 4 ], was prepared by the reaction of imidazole and trichloroacetatocopper(II). The Cu II atom adopts a distorted octahedral coordination geometry, binding the N atoms of four imidazole ligands and the carboxylate O atoms of two trichloroacetate anions. The molecular structure and packing are stabilized by N-HÁ Á ÁO hydrogen-bonding interactions. Close intermolecular ClÁ Á ÁCl contacts [3.498 (3) Å ] are also found in the structure.
The title structure contains one copper(II) cation, four imidazole ligands and two trichloroacetate anions. The coordination sphere of the copper(II) ion is best described as a slightly distorted octahedron. The Cu-N bond lengths are in agreement with those reported recently (Moncol et al., 2007). The crystal packing is stabilized by C-H···O and N-H···O hydrogen interaction (Table 1).

Experimental
The title compound was obtained by adding imidazole(4 mmol) dropwise to a solution of copper(II) trichloroacetate acid (1 mmol) in ethanol (30 ml) with stirring for 1 hour at room temperature. A blue solution formed and after a few days rod-like crystals precipitated.

Refinement
All H-atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.93Å, U iso =1.2U eq (C) for aromatic H atoms and 0.86Å, U iso = 1.2U eq (N) for the NH groups.

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