catena-Poly[[bis(5-chloro-2-nitrobenzoato)copper(II)]-bis(μ-5-chloro-2-nitrobenzoato)]

In the title compound, [Cu2(C7H3ClNO4)4]n, the coordination geometry around each CuII ion is distorted square-pyramidal. The CuO5 coordination is formed by five O atoms from the carboxylate groups of five 5-chloro-2-nitrobenzoate ligands. This coordination leads to the formation of centrosymmetric binuclear units which are edge-shared, forming a linear chain along the a axis, with the CuII ions alternately separated by 2.5891 (4) and 3.1763 (4) Å. The chains are interconnected into a three-dimensional network by C—H⋯O interactions.

In the title compound, [Cu 2 (C 7 H 3 ClNO 4 ) 4 ] n , the coordination geometry around each Cu II ion is distorted square-pyramidal. The CuO 5 coordination is formed by five O atoms from the carboxylate groups of five 5-chloro-2-nitrobenzoate ligands. This coordination leads to the formation of centrosymmetric binuclear units which are edge-shared, forming a linear chain along the a axis, with the Cu II ions alternately separated by 2.5891 (4) and 3.1763 (4) Å . The chains are interconnected into a three-dimensional network by C-HÁ Á ÁO interactions.
In the title compound, the coordination geometry around each Cu II ion can be described as square-pyramidal, formed by five O atoms from the carboxylate groups of five 5-chloro-2-nitrobenzoate ligands. The basal plane positions are occupied by atoms O5, O6A, O2B and O1C with an average Cu-O bond length of 1.962 (2) Å. The apical position is occupied by atom O1 (Fig.1). The Cu1 atom is displaced away from the basal plane by 0.1689 (3) Å and the Cu-Cu(-x,y,1 -z) separation is 2.5891 (4) Å. Similar CuO 5 coordination were observed in related structures reported by Kabbani et al. (2004) and Stachová et al. (2004). The CuO 5 square pyramids are edge-shared to form a linear polymeric chain along the a axis. In the chain, the Cu II ions are alternately separated by 2.5891 (4) and 3.1763 (4) Å.
The polymeric chains are interconnected through C-H···O intramolecular interactions, forming a three-dimensional network (Table 2 and Fig. 2).

S2. Experimental
An ethanol solution (50 ml) of 5-chloro-2-nitrobenzoic acid (4.84 g, 0.024 mol) was added to a solution of copper(II) sulfate pentahydrate (3.00 g, 0.012 mol) in ethanol (50 ml) and the mixture was stirred and refluxed for 2 h. The resulting solution was filtered and left to cool down to room temperature. After a few days of slow evaporation, blue crystals suitable for X-ray analysis were collected.

S3. Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).   The crystal packing of the title compound, viewed down the a axis. Hydrogen bonds are shown as dashed lines.

catena-Poly[[bis(5-chloro-2-nitrobenzoato)copper(II)]-bis(µ-5-chloro-2-nitrobenzoato)]
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.72 e Å −3 Δρ min = −1.04 e Å −3 Special details Experimental. The data was collected with the Oxford Cryosystem Cobra low-temperature attachment 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 > σ(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.