Potassium N-bromo-2-nitrobenzenesulfonamidate monohydrate

In the title compound, K+·C6H4BrN2O4S−·H2O, the K+ ion is hepta-coordinated by two O atoms from two different water molecules, three sulfonyl O atoms from three N-bromo-2-nitro-benzenesulfonamidate anions and two nitro O atoms from two N-bromo-2-nitro-benzenesulfonamidate anions. The S—N distance of 1.576 (4) Å is consistent with an S=N double bond. The crystal structure is stabilized by intermolecular O—H⋯N and O—H⋯Br hydrogen bonds which link the molecules into polymeric layers running parallel to the bc plane.

In the title compound, K + ÁC 6 H 4 BrN 2 O 4 S À ÁH 2 O, the K + ion is hepta-coordinated by two O atoms from two different water molecules, three sulfonyl O atoms from three N-bromo-2nitro-benzenesulfonamidate anions and two nitro O atoms from two N-bromo-2-nitro-benzenesulfonamidate anions. The S-N distance of 1.576 (4) Å is consistent with an S N double bond. The crystal structure is stabilized by intermolecular O-HÁ Á ÁN and O-HÁ Á ÁBr hydrogen bonds which link the molecules into polymeric layers running parallel to the bc plane.
In the title compound (I), the K + ion is hepta coordinated by two O atoms from two different water molecules, three sulfonyl O atoms from three N-bromo-2-nitro-benzenesulfonamidate anions and two nitro O atoms from two N-bromo-2nitro-benzenesulfonamidate anions (Fig 2.). This is in contrast to K + ion hepta coordination by three O atoms from water molecules and by four sulfonyl O atoms of three N-bromo-2-chloro-benzenesulfonamide anions in (II) and three Nbromo-2-methyl-benzenesulfonamide anions in (III).
The S-N distance of 1.576 (4) Å in (I) is consistent with an S-N double bond and is in agreement with the observed values of 1.582 (4) Å in (II) and 1.577 (5) Å in (III).

Experimental
The title compound was prepared by a method similar to the one described by Gowda & Mahadevappa (Gowda & Mahadevappa, 1983) and Usha & Gowda (Usha & Gowda, 2006). 2 g of 2-nitrobenzenesulfonamide was dissolved with stirring in 40 ml of 5M KOH at room temperature. The resultant solution was cooled in ice and 4 ml of liquid bromine was added drop wise with constant stirring. The resultant potassium salt of N-bromo-2-nitro-benzenesulfonamidate monohydrate was filtered under suction, washed quickly with a minimum quantity of ice cold water. The purity of the compound was checked by determining its melting point (175-177°C) and estimating, iodometrically, the amount of active bromine present in it. It was further characterized from its infrared spectrum. The characteristic absorptions observed are 3624.3, 3333.0, 3192.2, 2978.1, 2922.2, 2075.4, 1626.0, 1602.9, 1477.5, 1452.4, 1242.2, 1122.6, 1060.9, 937.4, 817.8, 686.7, 640.4, 578.6, 549.6, 524.6 and 470.6 cm -1 .
Prism like yellow single crystals of the title compound used in the X-ray diffraction studies were obtained from its aqueous solution at room temperature.

Refinement
H atoms bonded to C were positioned with idealized geometry using a riding model with the aromatic C-H = 0.93 Å.
The O-bound H atoms were located in a difference map and were refined with restrained geometry (Nardelli, 1999), viz. O-H distances were restrained to 0.85 (2) Å and the H-H distance was restrained to 1.365 Å, thus leading to the angle of 107°. All H atoms were refined with isotropic displacement parameters set at 1.2 U eq of the parent atom. The residual electron-density features are located in the region of Br1. The highest peak and the deepest hole are 0.80 and 0.84 Å from Br1, respectivily.

Data collection
Oxford Diffraction Xcalibur diffractometer with Sapphire CCD detector Radiation source: fine-focus sealed tube Graphite monochromator Rotation method data acquisition using ω scans.

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.