1,2-Bis(2-chlorobenzylidene)hydrazine

The title Schiff base compound, C14H10Cl2N2, crystallizes with one half-molecule in the asymmetric unit. The mid-point of the N—N bond [1.418 (3) Å] lies on an inversion centre. The molecular skeleton is approximately planar, the largest deviation from the mean plane being 0.143 (4) Å for the N-bonded C atom. The crystal packing exhibits no classical intermolecular hydrogen bonds.

The title Schiff base compound, C 14 H 10 Cl 2 N 2 , crystallizes with one half-molecule in the asymmetric unit. The mid-point of the N-N bond [1.418 (3) Å ] lies on an inversion centre. The molecular skeleton is approximately planar, the largest deviation from the mean plane being 0.143 (4) Å for the Nbonded C atom. The crystal packing exhibits no classical intermolecular hydrogen bonds.
The molecular structure of the title compound has crystallographically imposed inversion symmetry located in the middle of the N-N bond (Fig. 1). The molecule is approximately planar with the largest deviation from the plane being 0.143 (4) for C7. The C7-N1 of 1.272 (2)Å is indicative of a C?N double bond. The other C-N, C-Cl, and C-C distances show no remarkable features (Allen, 2002).

S2. Experimental
Under nitrogen, a mixture of 2-chlorobenzaldehyde (2.8 g, 20 mmol), Na 2 SO 4 (3.0 g) and hydrazine (30% in water, 10 mmol) in absolute ethanol (70 ml) was refluxed for about 3 h to yield a yellow precipitate. The product was collected by vacuum filtration and washed with ethanol. The crude solid was redissolved in CH 2 Cl 2 (100 ml) and washed with water (2*10 ml)and brine(10 ml). After dried over Na 2 SO 4 , the solvent was removed under vacuum, and yellow solid was isolated in yield 90% (2.5 g). Colourless single crystals of the compound suitable for X-ray analysis were grown from CH 2 Cl 2 and absolute ethanol(3:1) by slow evaporation of the solvent at room temperature over a period of about two weeks.

S3. Refinement
All H atoms were placed in calculated positions (C-H = 0.93 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C).  The molecular structure of (I) showing the atomic numbering scheme and 30% probability displacement ellipsoids [symmetry code (i):-x, 1 -y, 1 -z].

1,2-Bis(2-chlorobenzylidene)hydrazine
Crystal data C 14 H 10 Cl 2 N 2 M r = 277.14 Monoclinic, P2 1 /c Hall symbol: -P 2ybc a = 3.9449 (17)  Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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