4-Chloro-N′-(5-chloro-2-hydroxybenzylidene)benzohydrazide

The molecule of the title compound, C14H10Cl2N2O2, displays a trans configuration with respect to the C=N double bond and has an intramolecular O—H⋯N hydrogen bond. The dihedral angle between the two benzene rings is 1.4 (2)°. In the crystal structure, molecules are linked through intermolecular N—H⋯O hydrogen bonds, forming chains running along the a direction.

The molecule of the title compound, C 14 H 10 Cl 2 N 2 O 2 , displays a trans configuration with respect to the C N double bond and has an intramolecular O-HÁ Á ÁN hydrogen bond. The dihedral angle between the two benzene rings is 1.4 (2) . In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains running along the a direction.
The molecule of the title compound, displays a trans configuration with respect to the C═N double bond (Fig. 1). The dihedral angle between the two benzene rings is 1.4 (2)°. All the bond lengths are within normal ranges (Allen et al., 1987).
The C7═N1 bond length of 1.270 (3) Å conforms to the value for a double bond. The bond length of 1.343 (3) Å between atoms C8 and N2 is intermediate between a N-N single bond and a N═N double bond, because of conjugation effects in the molecule. There is a strong intramolecular hydrogen bond between the hydroxyl hydrogen and N1.
In the crystal structure, molecules are linked through intermolecular N-H···O hydrogen bonds (Table 1), forming chains running along the a direction (Fig. 2).
Experimental 5-Chlorosalicylaldehyde (0.1 mmol, 15.6 mg) and 4-chlorobenzohydrazide (0.1 mmol, 17.0 mg) were dissolved in MeOH (10 ml). The mixture was stirred at room temperature to give a clear colorless solution. Crystals of the title compound were formed by gradual evaporation of the solvent over a period of 13 days at room temperature.

Refinement
Atom H2 was located in a difference Fourier map and refined isotropically, with N-H distance restrained to 0.90 (1) Å.
Other H atoms were placed in idealized positions and constrained to ride on their parent atoms, with O-H distance of 0.82 Å, C-H distances of 0.93 Å, and with U iso (H) = 1.2U eq (C) and 1.5U eq (O). Fig. 1. The structure of the title compound showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

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 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.