(E)-N′-(5-Bromo-2-methoxybenzylidene)-4-chlorobenzohydrazide

The title Schiff base compound, C15H12BrClN2O2, crystallizes with two independent molecules in the asymmetric unit. The molecules adopt an E configuration with respect to the C=N double bond. The dihedral angles between the benzene rings are 24.4 (2) and 9.4 (2)° in the two molecules. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds, forming chains running along the b axis.

As a continuation of work on such compounds, I report herein the crystal structure of the new Schiff base compound, (I), Figure 1.
The two unique molecules of (I) adopt trans configurations about the C═N double bonds. The bond lengths and bond angles are within normal ranges and comparable to those observed in other similar Schiff bases (Tang, 2007(Tang, , 2008Yang et al., 2008). The C8-N1 and C23-N3 bond lengths are respectively 1.268 (4) and 1.281 (5) Å, indicating they are double bonds while the C9-N2 and C24-N4 distances are 1.352 (5) and 1.349 (5) Å respectively, indicating some degree of conjugation in the molecules. The dihedral angle between the C1-C6 and C10-C15 benzene rings is 24.4 (2) ° with a 9.4 (2) ° angle between the C16-C21 and C25-C30 rings. The crystal structure is stabilized by intermolecular N-H···O hydrogen bonds (Table 1), forming chains running along the b axis ( Figure 2).
Experimental 5-Bromo-2-methoxybenzaldehyde (21.5 mg, 0.1 mmol) and 4-chlorobenzohydrazide (17.0 mg, 0.1 mmol) were dissolved in MeOH (10 ml). The mixture was stirred at room temperature for 5 min to give a colorless solution. Colorless needle-like crystals of (I) were obtained from this solution on standing.

Refinement
Atoms H2 attached to N2 and H4A attached to N4 were located in a difference Fourier map and refined isotropically, with N-H distances restrained to be 0.90 (1) Å. Other H atoms were placed in the calculated positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93-0.96 Å, and with U iso (H) values set to 1.2U eq (C) and 1.5U eq (methyl C). Crystals of (I) were small and very weakly diffracting reducing the amount of data collected.
Figures Fig. 1. The asymmetric unit of (I) with displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. All e.s. 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.