4,6-Dichloro-2-[(E)-(2-{[(E)-3,5-dichloro-2-oxidobenzylidene]azaniumyl}ethyl)iminiumylmethyl]phenolate

The asymmetric unit of the title compound, C16H12Cl4N2O2, comprises half of a potentially tetradentate Schiff base ligand, located about a twofold rotation axis which bisects the central C—C bond of the ethane-1,2-diamine group. In the solid state, the compound exists in the zwitterionic form. There are two intramolecular N—H⋯O hydrogen bonds making S(6) ring motifs. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming two-dimensional frameworks which lie parallel to (100). There are also short Cl⋯Cl [3.4395 (9) Å] contacts present.

The asymmetric unit of the title compound, C 16 H 12 Cl 4 N 2 O 2 , comprises half of a potentially tetradentate Schiff base ligand, located about a twofold rotation axis which bisects the central C-C bond of the ethane-1,2-diamine group. In the solid state, the compound exists in the zwitterionic form. There are two intramolecular N-HÁ Á ÁO hydrogen bonds making S(6) ring motifs. In the crystal, molecules are linked by C-HÁ Á ÁO hydrogen bonds, forming two-dimensional frameworks which lie parallel to (100). There are also short ClÁ Á ÁCl [3.4395 (9) Å ] contacts present.
The asymmetric unit of the title compound, Fig. 1, comprises half of a potentially tetradentate Schiff base ligand that exists in the keto-amine tautomeric form. The molecule is located about a two-fold rotation axis which bisects the central C8-C8a bond of the ethane-1,2-diamine group. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The intramolecular N-H···O hydrogen bonds make S(6) ring motifs (Table 1; Bernstein et al., 1995).
In the crystal, molecules are linked by C-H···O hydrogen bonds along the b and c axes directions, forming two dimensional networks which lie parallel to the bc plane [ Table 1 and Fig. 2]. There are also short Cl···Cl ii [3.4384 (10)Å; symmetry code: (ii) -x, y, 1/2 -z] contacts present, which are shorter than the sum of the van der waals radius of Cl atoms (Bondi, 1964; Fig. 3).

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

Refinement
The N-bound H atom was located in a difference Fourier map. It was constrained to ride on the parent N-atom with U iso (H) = 1.2 U eq (N). The C-bound H atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 and 0.97 Å for CH and CH 2 H atoms, respectively, with U iso (H) = 1.2U eq (C).

Figure 2
The crystal packing of the title compound viewed down the c-axis, showing hoe the molecules are linked via C-H···O interactions (dashed lines), so forming two dimensional networks (see Table 1 for details).  The crystal packing diagram of the title compound viewed down the b-axis, showing the short intermolecular Cl···Cl contacts (dashed lines). All H atoms have been omitted for clarity.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.24 e Å −3 Δρ min = −0.28 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.