2-Chloro-N′-(2-hydroxy-3,5-diiodobenzylidene)benzohydrazide

In the title compound, C14H9ClI2N2O2, the dihedral angle between the benzene rings is 65.9 (2)° and an intramolecular O—H⋯N hydrogen bond generates an S(6) ring. The molecule has an E conformation about the C=N bond. In the crystal, molecules are linked into C(4) chains propagating in [001] by N—H⋯O hydrogen bonds.

In the title compound, C 14 H 9 ClI 2 N 2 O 2 , the dihedral angle between the benzene rings is 65.9 (2) and an intramolecular O-HÁ Á ÁN hydrogen bond generates an S(6) ring. The molecule has an E conformation about the C N bond. In the crystal, molecules are linked into C(4) chains propagating in [001] by N-HÁ Á ÁO hydrogen bonds.
The molecular structure of the title compound is shown in Fig. 1. The bond distances and angles are normal (Allen et al., 1987). The dihedral angle between the two benzene rings is 65.9 (2)°. The molecule of the compound displays an E geometry about the C═N bond. The molecules are linked into chains along the c axis by intermolecular N-H···O hydrogen bonds ( Fig. 2 and Table 1).
Experimental 2-Hydroxy-3,5-diiodobenzaldehyde (1.0 mmol, 373.9 mg) was dissolved in methanol (50 ml), then 2-chlorobenzohydrazide (1.0 mmol, 170.6 mg) was added slowly into the solution, and the mixture was kept at reflux with continuous stirring for 2 h. After the solution had cooled to room temperature colourless powder crystals appeared. The powder crystals were filtered and washed with methanol for three times. Recrystallization from absolute methanol yielded colourless block-shaped single crystals of the title compound.

Refinement
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 calculated positions with O-H = 0.82 Å, C-H = 0.93 Å, and refined in riding mode with U iso (H) = 1.2U eq (C) and 1.5U eq (O). Fig. 1

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.