1,3-Bis(4-fluorophenyl)-N,N′-(propane-1,3-diylidene)dihydroxylamine

The title compound, C15H12F2N2O2, crystallizes with two molecules (A and B) in the asymmetric unit. Both aromatic rings of both molecules are disordered over two orientations [occupancy ratios of 0.768 (3):0.232 (3) and 0.770 (3):0.230 (3) for molecule A and 0.789 (3):0.211 (3) and 0.789 (3):0.211 (3) for molecule B]. The dihedral angles between the planes of the major and minor components of the disordered aromatic rings are 72.0 (4) and 71.2 (4)° for molecule A, and 70.2 (4) and 71.5 (2)° for molecule B. In the crystal, both molecules form inversion dimers with R 2 2(6) ring motifs via pairs of intermolecular O—H⋯N hydrogen bonds. The dimers are linked, forming zigzag C(7) chains along the c axis. Weak C—H⋯π interactions help to consolidate the packing.

The title compound, C 15 H 12 F 2 N 2 O 2 , crystallizes with two molecules (A and B) in the asymmetric unit. Both aromatic rings of both molecules are disordered over two orientations . The dihedral angles between the planes of the major and minor components of the disordered aromatic rings are 72.0 (4) and 71.2 (4) for molecule A, and 70.2 (4) and 71.5 (2) for molecule B. In the crystal, both molecules form inversion dimers with R 2 2 (6) ring motifs via pairs of intermolecular O-HÁ Á ÁN hydrogen bonds. The dimers are linked, forming zigzag C(7) chains along the c axis. Weak C-HÁ Á Á interactions help to consolidate the packing.

Comment
In continuation of our work on the syntheses and structures of derivatives of 4,4'-difluoro chalcones and oximes (Fun et al., 2010a,b;Jasinski et al., 2010a,b;Baktır et al., 2011a,b), the title compound (I) was prepared and its crystal structure is now reported.
In the title compound (I), two symmetry independent molecules 1 (with F1A) and 2 (with F1B) exist in the asymmetric unit. Fig. 1 shows one of them. The dihedral angles between the planes of the major and minor components of the disordered aromatic rings of (I) are 72.0 (4)°, 71.2 (4)° for molecule 1, and 70.2 (4)°, 71.5 (2)° for molecule 2, respectively. The dihedral angle between the two aromatic rings is 89.09 (17) (6) ring motifs (Bernstein et al., 1995). These interactions link the symmetry-related molecules into as infinite zigzag chains along the c axis (Fig. 3). In addition, C-H···π interactions are observed (Table 1).

Experimental
A solution of 2,3-dibromo-1,3-bis(4-fluorophenyl)propan-1-one (4.04 g, 0.01 mol) and hydroxylamine hydrochloride (1.4 g, 0.02 mol) in 25 ml e thanol containing 5 ml of triethylamine was refluxed for 12 h. The reaction mixture was cooled and poured into 50 ml ice-cold water. The precipitate formed was collected by filtration and dried. Colourless prisms of (I) were grown from DMSO by slow evaporation and yield of the compound was 72%. (m.p. 485 K).   Fig. 1. One of the two molecules of (I) in the asymmetric unit, showing displacement ellipsoids for non-H atoms drawn at the 30% probability level.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.