N,N′-Bis(3,5-dichlorobenzylidene)ethane-1,2-diamine

The molecule of the title Schiff base compound, C16H12Cl4N2, lies across an inversion centre and adopts an E configuration with respect to the azomethine C=N bond. The imine groups are coplanar with the aromatic rings. Within the molecule, the planar units are parallel but extend in opposite directions from the dimethylene bridge. In the crystal structure, molecules are linked together by intermolecular C—H⋯Cl hydrogen bonds along the a axis.

The molecule of the title Schiff base compound, C 16 H 12 Cl 4 N 2 , lies across an inversion centre and adopts an E configuration with respect to the azomethine C N bond. The imine groups are coplanar with the aromatic rings. Within the molecule, the planar units are parallel but extend in opposite directions from the dimethylene bridge. In the crystal structure, molecules are linked together by intermolecular C-HÁ Á ÁCl hydrogen bonds along the a axis.

N,N'-Bis(3,5-dichlorobenzylidene)ethane-1,2-diamine
H.-K. Fun and R. Kia Comment Schiff bases are among the most prevalent mixed-donor ligands in the field of coordination chemistry in which there has been growing interest, mainly because of their wide applications in areas such as biochemistry, synthesis, and catalysis (Pal et al., 2005;Hou et al., 2001;Ren et al., 2002). Many Schiff base complexes have been structurally characterized, but only a relatively small number of free Schiff bases have had their X-ray structures reported (Calligaris & Randaccio, 1987). As an extension of our work (Fun, Kargar & Kia 2008;Fun, Kia & Kargar 2008) on the structural characterization of Schiff base ligands, the title compound (I), is reported here.
The molecule of the title compound ( Fig. 1), lies across an inversion centre and adopts an E configuration with respect to the azomethine C═N bond. The bond lengths and angles are within normal ranges (Allen et al., 1987) and are comparable with the values found in related structures (Fun & Kia (2008a,b,c); Fun, Kargar & Kia 2008;Fun, Kia & Kargar 2008).
The two planar units are parallel but extend in opposite directions from the dimethylene bridge. In the crystal structure, molecules are linked together by intermolecular C-H···Cl hydrogen bonds along the a-axis.

Experimental
The synthetic method has been described earlier (Fun, Kargar, & Kia, 2008). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

Refinement
All of the hydrogen atoms were located from the difference Fourier map and refined freely. The highest peak is located 0.63 Å from C7 and the deepest hole is located 0.55 Å from Cl2. Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms. The suffix A corresponds to symmetry code (-x + 2, -y, -z + 1).

Special details
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.
supplementary materials sup-3 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.