Bis(dimethylformamide-κO){4,4′,6,6′-tetrachloro-2,2-[butane-1,4-diyl(nitrilomethanylylidene)]diphenolato-κ4 O,N,N′,O′}nickel(II)

In the title Schiff base complex, [Ni(C18H14Cl4N2O2)(C3H7NO)2], the geometry around the NiII atom is distorted octahedral. It is coordinated by the N2O2 donor atoms of the tetradentate Schiff base ligand and the O atoms of two dimethylformamide molecules, which are cis to one another. The benzene rings are almost normal to each other [dihedral angle = 88.60 (14)°]. The various intramolecular C—H⋯O hydrogen bonds make S(5) and S(6) ring motifs. In the crystal, molecules are linked by pairs of weak C—H⋯Cl interactions, forming inversion dimers.

In the title Schiff base complex, [Ni(C 18 H 14 Cl 4 N 2 O 2 )-(C 3 H 7 NO) 2 ], the geometry around the Ni II atom is distorted octahedral. It is coordinated by the N 2 O 2 donor atoms of the tetradentate Schiff base ligand and the O atoms of two dimethylformamide molecules, which are cis to one another. The benzene rings are almost normal to each other [dihedral angle = 88.60 (14) ]. The various intramolecular C-HÁ Á ÁO hydrogen bonds make S(5) and S(6) ring motifs. In the crystal, molecules are linked by pairs of weak C-HÁ Á ÁCl interactions, forming inversion dimers.

Experimental
Crystal data [Ni(C 18 H 14 Table 1 Hydrogen-bond geometry (Å , ). In continuation of our work on the synthesis and crystal structure analysis of Schiff base ligands and their complexes (Kargar, Kia, Abbasian et al., 2012;Kargar, Kia, Ardakani et al., 2012;Kargar et al., 2011;Kia et al., 2010), we report herein on the synthesize and crystal structure of the title compound.
The asymmetric unit of the title compound, Fig. 1, comprises a Ni II Schiff base complex. The geometry around Ni II is distorted octahedral being coordinated by N 2 O 2 donor atoms of the tetradentate ligand, 6,6′-((butane-1,4-diylbis(azanylylidene))bis(methanylylidene)) bis(2,4-dichlorophenol) [Kargar, Kia, Ardakani et al., 2012] and by two oxygen atoms of dimethylformamide molecules that are cis to one another. The bond lengths (Allen et al., 1987) and angles are within the normal range. The intramolecular C-H···O hydrogen bonds makes S(5) and S(6) ring motif ( In the crystal structure molecules are linked by pairs of weak C-H···Cl interactions into individual inversion dimers (Table 1 and Fig. 2).

Experimental
The title compound was synthesized by adding 3,5-dichlorosalicylaldehyde-1,4-butylenediimine (1 mmol) to a solution of NiCl 2 .6H 2 O (1.1 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for 30 min. The resultant solution was filtered. Green prismatic single crystals of the title compound, suitable for X-ray structure determination, were obtained by recrystallization from ethanol on slow evaporation of the solvents at room temperature over several days.

Refinement
The H-atoms were included in calculated positions 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 × U eq (parent C-atom), where k = 1.5 for CH 3 H-atoms and = 1.2 for other H-atoms.  The molecular structure of the title compound, showing 40% probability displacement ellipsoids and the atomic numbering. Dashed lines show the intramolecular C-H···O interactions (see Table 1 for details).

Figure 2
The crystal packing of the title compound viewed along the a axis, showing linking of molecules through weak C-H···Cl interactions (dashed lines; see Table 1  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.39 e Å −3 Δρ min = −0.58 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