Tetrakis(μ-4-chlorobenzoato-κ2 O:O′)bis[(ethanol-κO)copper(II)](Cu—Cu)

In the centrosymmetric dinuclear title CuII complex, [Cu2(C7H4ClO2)(C2H5OH)2], the Cu—Cu distance is 2.5905 (4) Å. The two metal atoms are bridged by four 4-chlorobenzoate ligands and each has an ethanol molecule in the axial position of the overall octahedral coordination environment. The crystal packing features O—H⋯O hydrogen bonds.

In the centrosymmetric dinuclear title Cu II complex, [Cu 2 (C 7 H 4 ClO 2 )(C 2 H 5 OH) 2 ], the Cu-Cu distance is 2.5905 (4) Å . The two metal atoms are bridged by four 4chlorobenzoate ligands and each has an ethanol molecule in the axial position of the overall octahedral coordination environment. The crystal packing features O-HÁ Á ÁO hydrogen bonds.

Comment
The chemistry of metal-coordination polymers has been advanced due to their diverse topologies and potential applications in smart optoelectronic, magnetic, microporous and biomimetic materials with specific structures, properties, and reactivities (Deka et al., 2006;Eddaoudi et al., 2001). A coordination polymer contains one or more center of metal  (Tables 1).

Experimental
The reagents used here were purchased from commercial sources (Sigma-Aldrich). To synthetize the title complex 1 ml of Copper(II) Chloride (0,1 mmol; 100mM) were added to a water (3 ml) / ethanol (3 ml) mixture containing 0,0134 g of melanine and 0,017 g of acid p-Chlorobenzoic. The reaction was sealed in a Teflon-lined stainless steel autoclave, which was heated at 130°C for 3 days under autogenous pressure. After slow cooling to room temperature in 6 h. In this conditions are formed green crystals of the complex and colourless crystal of melamine. A suitable sample of the green crystals has been selected by optical microscope and used in X-Ray structure determination.

Refinement
The structure was solved by direct method and subsequent Fourier difference techniques and refined using full-matrix least-squares procedure on F 2 with anisotropic thermal parameters for all non-hydrogen atoms (SHELXL97). All non hydrogen atoms were refined anisotropically. Several hydrogen atoms were located on the final difference map, the H atoms were included in the refinement via the "riding model" method with the X-H bond geometry and the H isotropic displacement parameter depending on the parent atom X. Owing to the usual conformational disorder of the terminal ethanol, no suitable bond/angles constrain was introduced during the last refinement cycles so that the ligand geometry appears distorted but similar to the reported values in analogous complexes.  assembled by weak π-stacking and chlorine-phenyl interactions. Displacement ellipsoids are plotted at a 30% probability level and H atoms are drawn with an arbitrary radius.

Special details
Experimental. SADABS-2008/1 -Bruker AXS area detector scaling and absorption correction. wR2(int) was 0.0889 before and 0.0361 after correction. The crystals suitable for the X-ray analysis were obtained by solvothermal synthesis of the reaction of p-Chlorobenzoate with Copper(II) salt in water/ethanol (1:1) mixed together with melanin. 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 > 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.