Bis{(E)-4-bromo-2-[(2-chloro-3-pyridyl)iminomethyl]phenolato-κ2 N,O}copper(II)

In the title complex, [Cu(C12H7BrClN2O)2], the CuII center is tetracoordinated by two phenolate O and two azomethine N atoms from two independent bidentate 4-bromo-2-[(2-chloro-3-pyridyl)iminomethyl]phenolate (L) ligands. In the crystal structure, the CuII atom has a distorted square-planar coordination environment. The interplanar dihedral angles between the benzene and pyridine rings in the individual ligands are 63.83 (4) and 54.43 (3)°, indicating the pyridine ring to have considerably weaker steric hindrance.

In the title complex, [Cu(C 12 H 7 BrClN 2 O) 2 ], the Cu II center is tetracoordinated by two phenolate O and two azomethine N atoms from two independent bidentate 4-bromo-2-[(2-chloro-3-pyridyl)iminomethyl]phenolate (L) ligands. In the crystal structure, the Cu II atom has a distorted square-planar coordination environment. The interplanar dihedral angles between the benzene and pyridine rings in the individual ligands are 63.83 (4) and 54.43 (3) , indicating the pyridine ring to have considerably weaker steric hindrance.

Experimental
Crystal data [Cu(C 12  Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL. This work was supported by the Foundation of the Education Department of Gansu Province and the 'Jing Lan' Talent Engineering Funds of Lanzhou Jiaotong University, which are gratefully acknowledged.

S1. Comment
Phenoxy-imines are a versatile class of ligands that display a truly impressive range of diverse applications spanning from bioinorganic chemistry to coordination chemistry, chemical catalysis, and materials related applications (John et al., 2007). Due to their chelating ability and positive redox potential many copper(II) complexes are generally biologically active (Karmaka et al., 2007). As part of our ongoing research into the complexes between transition metals and phenoxy-imine ligands, we report here the synthesis and crystal structures of the title complex, bis{(E)-[4-bromo-2-((2chloropyridin-3-ylimino)methyl-κN)] phenolato-κO 1 }copper(II) (Fig. 1).
In the asymmetric molecule unit of the title complex, the Cu II center is tetracoordinated by two phenolic O and two azomethine N atoms from two ligand (L -) units and has a distorted square-planar coordination environment, which is similar to the salen-type bisoxime complexes (Dong et al., 2009a, Dong et al., 2009b. It was observed that all bond lengths are within normal ranges (Allen et al., 1987).
The color of the mixing solution turned to yellow immediately, then turned to brown slowly and allowed to stand at room temperature for several days. With evaporation of the solvent, dark-brown needle-like single crystals suitable for X-ray crystallographic analysis were obtained. IR: ν C=N, 1600 cm -1 , ν Ar-O, 1242 cm -1 , ν Cu-N, 445 cm -1 and ν Cu-O, 424 cm -1 .

Special details
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.