Bis[2-(hy-droxy-imino)-cyclo-hexan-1-one oximato-κ(2) N,N']copper(II).

In the title compound, [Cu(C6H9N2O2)2], the Cu(II) atom is located on an inversion center and has a square-planar environment. Two 2-(hy-droxy-imino)-cyclo-hexan-1-one oxim-ate monoanions chelate to the Cu(II) atom and the Cu-N distances are 1.920 (3) and 1.930 (3) Å. There are two short intra-molecular O-H⋯O hydrogen bonds between the ligands. The complex mol-ecules stack into columns extended along the c axis, with a Cu⋯Cu distance between adjacent mol-ecules of 3.3060 (3) Å.

In the title compound, [Cu(C 6 H 9 N 2 O 2 ) 2 ], the Cu II atom is located on an inversion center and has a square-planar environment. Two 2-(hydroxyimino)cyclohexan-1-one oximate monoanions chelate to the Cu II atom and the Cu-N distances are 1.920 (3) and 1.930 (3) Å . There are two short intramolecular O-HÁ Á ÁO hydrogen bonds between the ligands. The complex molecules stack into columns extended along the c axis, with a CuÁ Á ÁCu distance between adjacent molecules of 3.3060 (3) Å .
In the title coordination compound, the Cu II atom has a square-planar geometry being coordinated by four N atoms from two monodeprotonated dioxime ligands (Fig.1). The monodeprotonated 1,2-cyclohexanedionedioxime coordinates in a typical bidentate mode through its oxime nitrogen atoms, thus leading to the formation of a five-membered chelate ring around the metal core with a N1-Cu1-N2 angle of 82.84 (12)° and slightly asymmetric Cu-N distances of 1.920 (3) and 1.930 (3) Å. The cyclohexyl ring of the 1,2-cyclohexanedionedioxime molecule adopts a half-boat conformation.
Two dioxime residues are connected via O-H···O hydrogen bonds, typical for all bis-ligand complexes of α -dioximes (Table 1). The packing of the molecules involves columns of Cu atoms with a Cu-Cu separation of 3.3060 (3) Å (Fig.2).

Experimental
The title compound was obtained by disolving 0.02 g of copper acetate dihydrate and 0.028 g of 1,2-cyclohexanedionedioxime in the 30 ml methanol/dimethylformamide 1:5 (v/v) mixture. The resulting solution was boiled for ca 7 min, filtered off, and then slowly cooled to room temperature resulting in needle-shaped brown crystals (yield: 40%).

Refinement
The C-bound hydrogen atoms were placed in calculated positions and were treated using a riding model approximation [U iso (H) = 1.2U eq (C)]. The O-bound hydrogen atoms were found from electron-density difference maps and refined freely.

Figure 2
The crystal packing of the title compound.

Bis[2-(hydroxyimino)cyclohexan-1-one oximato-κ 2 N,N′]copper(II)
Crystal data [Cu(C 6  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 > 2sigma(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.