(E)-Methyl 3-(3,5-dibromo-2-hydroxybenzylidene)carbazate

The title compound, C9H8Br2N2O3, crystallizes with two very similar independent molecules in the asymmetric unit, each of which adopts a trans configuration with respect to the C=N bond. Intramolecular O—H⋯N hydrogen bonds are observed in each independent molecule. In the crystal structure, molecules are linked into chains propagating along [010] by N—H⋯O and C—H⋯O hydrogen bonds. In addition, C—H⋯π interactions stabilize the structure.

The title compound, C 9 H 8 Br 2 N 2 O 3 , crystallizes with two very similar independent molecules in the asymmetric unit, each of which adopts a trans configuration with respect to the C N bond. Intramolecular O-HÁ Á ÁN hydrogen bonds are observed in each independent molecule. In the crystal structure, molecules are linked into chains propagating along [010] by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds. In addition, C-HÁ Á Á interactions stabilize the structure.

Comment
Benzaldehydehydrazone derivatives have attracted much attention due to their pharmacological activity (Parashar et al., 1988) and their photochromic properties (Hadjoudis et al., 1987). They are important intermediates of 1,3,4-oxadiazoles, which have been reported to be versatile compounds with many interesting properties (Borg et al., 1999). Metal complexes based on Schiff bases have received considerable attention because they can be utilized as model compounds of active centres in various proteins and enzymes (Kahwa et al., 1986;Santos et al., 2001). We report here the crystal structure of the title compound (Fig. 1).
In the crystal structure, the molecules are linked into chains running along the [010] by N-H···O and C-H···O hydrogen bonds. In addition, intermolecular C-H···π interactions are observed, which further stabilize the structure (Table 1).
Experimental 3,5-Dibromo-2-hydroxybenzaldehyde (2.79 g, 0.01 mol) and methyl hydrazinecarboxylate (0.90 g, 0.01 mol) were dissolved in stirred methanol (15 ml) and left for 5.5 h at room temperature. The resulting solid was filtered off and recrystallized from ethanol to give the title compound in 96% yield. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ispropanol solution at room temperature (m.p. 415-417 K).

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.