N-(2-Amino-5-chlorophenyl)-2-bromobenzenesulfonamide

In the title compound, C12H10BrClN2O2S, the sulfonamide group adopts a staggered conformation about the N—S bond [the C—S—N—H torsion angle is 97 (3)°] with the N-atom lone pair bisecting the O=S=O angle. For the C(Ar)—S bond, the ortho-substituted C atom bisects one of O=S–N angles [the C—C—S—N torsion angle is −57.7 (3)°]. The mean planes of the aromatic rings form a dihedral angle of 75.1 (1)°. In the crystal, molecules form inversion dimers through pairs of N—H⋯NH2 hydrogen bonds. The molecules are further consolidated into layers along the bc plane by weaker N—H⋯O interactions.

In the title compound, C 12 H 10 BrClN 2 O 2 S, the sulfonamide group adopts a staggered conformation about the N-S bond [the C-S-N-H torsion angle is 97 (3) ] with the N-atom lone pair bisecting the O S O angle. For the C(Ar)-S bond, the ortho-substituted C atom bisects one of O S-N angles [the C-C-S-N torsion angle is À57.7 (3) ]. The mean planes of the aromatic rings form a dihedral angle of 75.1 (1) . In the crystal, molecules form inversion dimers through pairs of N-HÁ Á ÁNH 2 hydrogen bonds. The molecules are further consolidated into layers along the bc plane by weaker N-HÁ Á ÁO interactions.

Comment
The study of the structural and conformational properties of the sulfonamide group (R-SO 2 -NR 2 ) is essential to the comprehension of the "sulfa drugs" action. They found applications as HIV inhibitors (Lu & Tucker, 2007), antimicrobial drugs (Tappe et al., 2008), carbonic anhydrase inhibitors (Chegwidden et al., 2000), anti-tumor agents (Purushottamachar et al., 2008), just to name a few. In this respect a lot of publications have appeared reporting structural data of compounds containing the sulfonamide function (Parkin et al., 2008, Altamura et al., 2009, Perlovich et al., 2009, Perlovich et al., 2011,Vega-Hissi et al., 2011, Altamura et al., 2012. The molecule, as expected, has a staggered conformation about the N-S bond, with the N lone pair bisecting the OŜO angle (Table 1, Fig. 1). The value of the dihedral angle C6-C1-S1 -O1 (Table 1) is also in the range observed for arylsulfonamides bearing a non-hydrogen atom in ortho position (a bromine atom in this case). The sulfonamide nitrogen atom is almost planar-trigonal (Σ<N=357 (3)°). The aromatic rings are almost perpendicular to each other with a dihedral angle of 75.1 (1)°. In the crystal, dimers are formed by a couple of complementary hydrogen bonds involving the nitrogen atom of the sulfonamide grouping as a donor and amino nitrogen as an acceptor (Table 2). Dimers form layers along bc plane through weaker NH 2 ···SO 2 H-bonds between the amino group and an oxygen atom of the sulfonamide moiety ( Table 2). The remaining amine H atom (HN2B) appears to be involved in

Refinement
The N-H H atoms were located in the Fourier difference map and their coordinates were refined with U(H) = 1.2U eq (N).
All other H atoms were positioned using idealized geometry and refined using a riding model with U(H) 1.2 times U eq (C).

Computing details
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: PARST (Nardelli, 1995).  The structure of the title compound showing labelling and displacement ellipsoids drawn at the 30% probability level.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.32 e Å −3 Δρ min = −0.38 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.09409 (