{4,4′,6,6′-Tetrabromo-2,2′-[(2,2-dimethylpropane-1,3-diyl)bis(nitrilomethanylylidene)]diphenolato}copper(II)

In the title compound, [Cu(C19H16Br4N2O2)], the CuII ion and the substituted C atom of the diamine fragment lie on a crystallographic twofold rotation axis. The geometry around the CuII ion is distorted square-planar, which is defined by the N2O2 donor atoms of the coordinated Schiff base ligand. The dihedral angle between the symmetry-related substituted benzene rings is 25.33 (14)°. The crystal structure is stabilized by an intermolecular π–π interaction [centroid–centroid distance = 3.8891 (18) Å].

In the title compound, [Cu(C 19 H 16 Br 4 N 2 O 2 )], the Cu II ion and the substituted C atom of the diamine fragment lie on a crystallographic twofold rotation axis. The geometry around the Cu II ion is distorted square-planar, which is defined by the N 2 O 2 donor atoms of the coordinated Schiff base ligand. The dihedral angle between the symmetry-related substituted benzene rings is 25.33 (14) . The crystal structure is stabilized by an intermolecularinteraction [centroid-centroid distance = 3.8891 (18) Å ].
The asymmetric unit of the title compound, Fig. 1, comprises half of a potentially tetradentate Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The Cu1 and C9 atoms lie on crystallographic two-fold rotation axis. The crystal structure is further stabilized by the intermolecular π-π interaction, (Fig. 2),

Experimental
The title compound was synthesized by adding 3,5-dibromo-salicylaldehyde-2,2-dimethyl-1,3-propanediamine (2 mmol) to a solution of CuCl 2 . 4H 2 O (2.1 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for half an hour. The resultant solution was filtered. Green single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
All hydrogen atoms were positioned geometrically with C-H = 0.93-0.97 Å and included in a riding model and treated as riding atoms: C-H = 0.93, 0.96 and 0.97 Å for CH, CH 3 and CH 2 H-atoms, respectively, with U iso (H) = k x U eq (C), where k = 1.5 for CH 3 H-atoms, and k = 1.2 for all other H-atoms..

Figure 2
The packing diagram of the title compound viewed down the b-axis showing linking of molecules through the intermolecular π-π intearctions (dashed lines). The hydrogen atoms omitted for clarity. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.58 e Å −3 Δρ min = −0.59 e Å −3 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq