(E,E)-N 1,N 2-Bis(2,6-difluorobenzylidene)ethane-1,2-diamine

The asymmetric unit of the title compound, C16H12F4N2, comprises half of the potentially bidentate Schiff base ligand, with an inversion centre located at the mid-point of the central C—C bond. The crystal packing is stabilized by intermolecular C—H⋯N and π–π interactions [centroid–centroid distance = 3.6793 (12) Å and interplanar spacing = 3.4999 (7) Å].

The asymmetric unit of the title compound, C 16 H 12 F 4 N 2 , comprises half of the potentially bidentate Schiff base ligand, with an inversion centre located at the mid-point of the central C-C bond. The crystal packing is stabilized by intermolecular C-HÁ Á ÁN andinteractions [centroid-centroid distance = 3.6793 (12) Å and interplanar spacing = 3.4999 (7) Å ].

Related literature
For background to the synthesis and structural variations of Schiff base ligands and their complexes, see: Granovski et al. (1993); Elmali et al. (2000).

Comment
Schiff base ligands are among the most prevalent ligands in the field of coordination chemistry. Metal derivatives of Schiff bases have been studied extensively, and Ni II and Cu II complexes play a major role in both synthetic and structural research (Elmali et al., 2000;Granovski et al., 1993).
The asymmetric unit of the title compound comprises half of the potentially bidentate Schiff base ligand; an inversion centre is located in the middle of the central C-C bond ( Fig. 1). Each half of the molecule is essentially planar, the imine segment (C1-N1═C2-C3) being rotated only 7.36 (10)° out of the plane of the benzene ring. The two halves are parallel by inversion symmetry, but not coplanar, the CH 2 CH 2 linker unit forming a step between them.

Experimental
The title compound was synthesized by mixing 2,4-difluorobenzaldehyde (4 mmol) and ethylenediamine (2 mmol) in chloroform (20 ml). After stirring for 2 h, the solution was filtered and the resulting yellow solid was crystallized from ethanol, giving single crystals suitable for X-ray diffraction.

Refinement
All H atoms were positioned geometrically and constrained to ride on the parent atoms, with C-H = 0.95-0.99Å and U iso (H) = 1.2 U eq (C). Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering. Symmetry code for suffix A: -x + 1, -y + 1, -z + 2.  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 > σ(F 2 ) is used only for calculating Rfactors(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.

Figures
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )