6-Bromo-1-methyl-4-[2-(4-nitrobenzylidene)hydrazin-1-ylidene]-2,2-dioxo-3,4-dihydro-1H-2λ6,1-benzothiazine

In the title compound, C16H13BrN4O4S, the dihedral angle between the aromatic rings is 4.1 (2)° and the C=N—N=C torsion angle is 175.5 (3)°. The nitro group is almost coplanar with the benzene ring to which it is attached [dihedral angle = 2.9 (7)°]. The thiazine ring has an S-envelope conformation with the S atom displaced by 0.819 (3) Å from the mean plane of the other five atoms (r.m.s. deviation = 0.017 Å). In the crystal, C—H⋯O interactions link the molecules and weak aromatic π–π stacking [centroid–centroid separation = 3.874 (2) Å] is also observed.


Muhammad Shafiq, William T. A. Harrison and Islam Ullah Khan Comment
A number of benzothiazine derivatives have been found to be effective as drugs (Shafiq, Zia-ur-Rehman et al., 2011). As a part of our ongoing studies in this area, we now describe the crystal structure of the title compound in this areticle.
The crystal packing (Fig. 2) is stabilized by weak intermolecular C-H···O hydrogen bonds (Table 1) linking the molecules to generate a three-dimensional network with all four O atoms acting as acceptors. Weak aromatic π-π stacking [centroid-centroid separation = 3.874 (2) Å] is also observed.

Experimental
The compound was synthesized following the literature procedure (Shafiq, Zia-ur-Rehman et al., 2011) and recrystalized from an ethylacetate solution under slow evaporation.

Refinement
The H atoms were placed in calculated positions (C-H = 0.93-0.97 Å) and refined as riding. The methyl group was allowed to rotate, but not to tip, to best fit the electron density. The constraint U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C) was applied. The (0 0 1) and (0 1 0) reflections were obstructed by the beamstop and were omitted from the refinement.  The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.58 e Å −3 Δρ min = −0.40 e Å −3

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.