4-Bromo-N-phenylbenzamidoxime

The title compound, C13H11BrN2O, a hydroxyamidine derivative (an amidoxime), was obtained by addition of the corresponding imidoyl chloride to hydroxylamine. The benzene and phenyl rings are twisted from the mean plane of the hydroxyamidine group by 34.4 (1) and 59.2 (1)°, respectively. In the crystal structure, intermolecular O—H⋯N hydrogen bonds link pairs of molecules, forming centrosymmetric dimers.

The title compound, C 13 H 11 BrN 2 O, a hydroxyamidine derivative (an amidoxime), was obtained by addition of the corresponding imidoyl chloride to hydroxylamine. The benzene and phenyl rings are twisted from the mean plane of the hydroxyamidine group by 34.4 (1) and 59.2 (1) , respectively. In the crystal structure, intermolecular O-HÁ Á ÁN hydrogen bonds link pairs of molecules, forming centrosymmetric dimers.

Comment
Although extensively studied for their biological activity (antituberculars, hypotensives), their pharmacological properties (bactericidal, fungicidal, local anaesthetics) (Srivastava, 1997) and also as precursors in the synthesis of cyclic compounds (Dürüst, 2000 and2008), N-substituted hydroxyamidines/amidoximes have been less investigated concerning their role in coordination and supramolecular chemistry. They act as bidentate ligands to form 5-membered chelate rings with metal ions, forming stable metal complexes. The good electronic delocalization presented by their structures, and the interesting design possibilities, suggest that N-substituted hydroxyamidines/amidoximes and their complexes could be successfully incorporated into supramolecular assemblies based on coordination chemistry and hydrogen bonding. Herein we report the synthesis and crystal structure of a new amidoxime derivative.
The molecular structure of the title compound is shown in Fig. 1. The amidoxime group is present in its neutral form, N-C=N-OH and the bond lengths and angles are within normal ranges (Allen, 1987). The mean planes of the benzene and phenyl rings are tilted with respect to each other by 64.63 (9) ° and, the amidoxime group forms dihedral angles with the benzene and the phenyl rings of 34.4 (1) and 59.2 (1)°, respectively. This value is less than that reported for the bulky substituted N-aryl compound (Krajete, 2004) due to the lesser influence of steric crowding in the title compound.
As illustrated in Fig. 2, the hydrogen bond is of crucial importance to the self-assembly. Molecules are paired by two hydrogen bonds involving the N-hydroxyl group rather than the amidoxime moieties. In the crystal structure, the N-hydroxyl groups participate in hydrogen bonding of the O-H···N type in which two molecules are joined via O-H···N hydrogen bonds to form a dimer across an inversion center (Table 1).

Experimental
The title compound was synthesized according to the procedure of Krajete et al. (2004). 4-Bromo-N-phenylbenzamide (1.5 g, 5.43 mmol) and an excess of thionyl chloride (15 ml) were refluxed for 2 h under nitrogen atmosphere, yielding the corresponding imidoyl chloirde as a pale yellow solid. This compound was dissolved in dry dichlorometane and added drop-wise to a mixture of hydroxylamine hydrochloride (0.4 g, 5.97 mmol) in anhydrous ethanol and triethylamine (3.8 ml, 27.1 mmol) in dry dichloromethane at 195K. The reaction mixture was brought to room temperature and then was heated at reflux for 16 h. The resulting yellow solution was washed with distillated water and the organic materials were subsequently extracted with diethyl ether, dried over anhydrous Na 2 SO 4 and filtered. X-ray quality crystals were obtained from a solution of the title compound in aqueous EtOH by slow evaporation at room temperature.  Fig. 1. The molecular structure of the title compound (50% probability displacement ellipsoids).

Special details
Experimental. X-ray crystallographic data for (I) were collected from a single-crystal sample, which was mounted on a loop fiber.
Data were collected using a Bruker Platform diffractometer, equipped with a Bruker SMART 4 K Charged-Coupled Device (CCD) Area Detector using the program APEX2 and a Nonius FR591 rotating anode equiped with a Montel 200 optics The crystal-to-detector distance was 5.0 cm, and the data collection was carried out in 512 x 512 pixel mode. The initial unit-cell parameters were determined by a least-squares fit of the angular setting of strong reflections, collected by a 10.0 degree scan in 33 frames over four different parts of the reciprocal space (133 frames total). One complete sphere of data was collected, to better than 0.80Å resolution. 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.