Tetra-μ-acetato-bis[(pyridine N-oxide)copper(II)](Cu—Cu)

The molecule of the title binuclear copper(II) complex, [Cu2(CH3COO)4(C5H5NO)2], occupies a special position on a crystallographic inversion centre; the coordination environment of the CuII atom is slightly distorted square-pyramidal and is made up of four O atoms belonging to four acetate groups in the basal plane with the O atom of pyridine N-oxide ligand in the apical position. The Cu—Cu distance is 2.6376 (6) Å.

The molecule of the title binuclear copper(II) complex, [Cu 2 (CH 3 COO) 4 (C 5 H 5 NO) 2 ], occupies a special position on a crystallographic inversion centre; the coordination environment of the Cu II atom is slightly distorted square-pyramidal and is made up of four O atoms belonging to four acetate groups in the basal plane with the O atom of pyridine N-oxide ligand in the apical position. The Cu-Cu distance is 2.6376 (6) Å .

Tetra-µ-acetato-bis[(pyridine N-oxide)copper(II)](Cu-Cu)
Yue Cui, Qian Gao, Chao-Yan Zhang and Ya-Bo Xie S1. Comment The crystal structures of binuclear copper(II) complexes have been extensively studied because of their possible anticarcinogen properties (Li et al., 2007), and numerous papers dealing with binuclear copper complexes have been published (Zhang, 2009). Herein, we report the synthesis and crystal structure of a new binuclear copper complex.
The molecule of the title binuclear copper(II) complex, [Cu 2 (C 2 H 3 O 2 ) 4 (C 5 H 5 ON) 2 ], occupies a special position in the crystallographic inversion centre; coordination environment of the Cu II atom represents a slightly distorted tetragonal pyramid and is made up of four oxygen atoms belonging to four acetato-group in the basal plane as well as the oxygen atom of pyridine N-oxide ligand in the apical position. The Cu-O bond distance between Cu II atom and acetato O atoms vary from 1.9605 (18) Å to 1.9710 (18) Å, while the Cu-O bond distance involving Cu II atom and the O atom of the

S2. Experimental
A solution containing a 1:2:5 molar ratio of picolinic acid N-oxide (0.0139 g, 0.1 mmol), CuCO 3 (0.0247 g, 0.2 mmol) and acetic acid (1 ml, 0.5 mmol/ml) in a mixture of ethanol(5 ml) and water (10 ml) was sealed in a 25 ml teflon reactor and kept at 453 K for 3 days, then slowly cooled to 373 k and kept at this temperature for 24 h more. After cooling to room temperature, the mixture was filtered and the filtrate was allowed to stand at room temperature. Block crystals suitable for the X-ray investigation were collected.

S3. Refinement
All H atoms were placed geometrically (C-H = 0.93-0.96 Å) and included into refinement in the riding motion approximation with U iso (H) = 1.2U eq (C) [1.5U eq (C) for methyl H atoms].  Molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level; hydrogen atoms are shown as small circles of arbitrary radius. The unlabelled atoms are derived by the symmetry transformation -x + 1, -y, -z.

Tetra-µ-acetato-bis[(pyridine N-oxide)copper(II)](Cu-Cu)
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.43 e Å −3 Δρ min = −0.33 e Å −3 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.  (7) H9A-C9-H9B 109.5