Potassium N-bromo-2,4-dichlorobenzenesulfonamidate sesquihydrate

The asymmetric unit of the title salt, K+·C6H3BrCl2NO2S−·1.5H2O, contains one K+ cation, one N-bromo-2,4-dichlorobenzenesulfonamidate anion, one water molecule in general position and one water molecule located on a twofold rotation axis. The K+ cation is hepta-coordinated by three water O atoms and four sulfonyl O atoms from three symmetry-related N-bromo-2,4-dichlorobenzenesulfonamide anions. The S=N distance of 1.575 (3) Å is consistent with that of a double bond. In the crystal, the anions are linked by O—H⋯Br and O—H⋯N hydrogen bonds into layers parallel to the ac plane.

The asymmetric unit of the title salt, K + ÁC 6 H 3 BrCl 2 NO 2 S À Á-1.5H 2 O, contains one K + cation, one N-bromo-2,4-dichlorobenzenesulfonamidate anion, one water molecule in general position and one water molecule located on a twofold rotation axis. The K + cation is hepta-coordinated by three water O atoms and four sulfonyl O atoms from three symmetry-related N-bromo-2,4-dichlorobenzenesulfonamide anions. The S N distance of 1.575 (3) Å is consistent with that of a double bond. In the crystal, the anions are linked by O-HÁ Á ÁBr and O-HÁ Á ÁN hydrogen bonds into layers parallel to the ac plane.
In the title compound, K + ion is hepta coordinated by three O atoms from water molecules and four sulfonyl O atoms of three different N-bromo-2,4-dichlorobenzenesulfonamide anions. The replacement of Na + by K + changes co-ordination from hexa to hepta in the structure (Gowda et al., 2007) and other parameters.
The S-N distance of 1.575 (3) Å is consistent with a S-N double bond and is in agreement with the observed values of 1.582 (4) Å in (II), 1.584 (6) Å in (III) and 1.590 (6) Å in (IV).
The asymmetric unit of (I) consists of one potassium cation, one N-bromo-2,4-dichlorobenzenesulfonamidate anion and one water molecule in general position and and one water molecule located on a twofold rotation axis.
In the crystal structure the anions are linked by intermolecular O-H···Br and O-H···N hydrogen bonding into layers, that are parallel to the ac plane ( Fig. 2 and Table 1).

Experimental
The title compound was prepared by a method similar to the one described by Gowda & Mahadevappa (Gowda & Mahadevappa, 1983). 2 g of 2,4-dichlorobenzenesulfonamide 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-2,4-dichlorobenzenesulfonamide 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 (203-205° C) and estimating, iodometrically, the amount of active bromine present in it. It was further characterized from its infrared spectrum.
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.