1-(4-Bromophenyl)-2-ethylsulfinyl-2-(phenylselanyl)ethanone monohydrate

In the title hydrate, C16H15BrO2SSe·H2O, the sulfinyl O atom lies on the opposite side of the molecule to the Se and carbonyl O atoms. The benzene rings form a dihedral angle of 51.66 (17)° and are splayed with respect to each other. The observed conformation allows the water molecules to bridge sulfinyl O atoms via O—H⋯O hydrogen bonds, generating a linear supramolecular chain along the b axis; the chain is further stabilized by C—H⋯O contacts. The chains are held in place in the crystal structure by C⋯H⋯π and C—Br⋯π interactions.

In the title hydrate, C 16 H 15 BrO 2 SSeÁH 2 O, the sulfinyl O atom lies on the opposite side of the molecule to the Se and carbonyl O atoms. The benzene rings form a dihedral angle of 51. 66 (17) and are splayed with respect to each other. The observed conformation allows the water molecules to bridge sulfinyl O atoms via O-HÁ Á ÁO hydrogen bonds, generating a linear supramolecular chain along the b axis; the chain is further stabilized by C-HÁ Á ÁO contacts. The chains are held in place in the crystal structure by CÁ Á ÁHÁ Á Á and C-BrÁ Á Á interactions.
We thank the Brazilian agencies FAPESP, CNPq (fellowships to JZS and PRO) and CAPES (808/2009 to JZS) for financial support.
With reference to the pyramidal-S atom, the sulfinyl-O lies to the opposite side of the molecule to each of the Se and carbonyl-O atoms. This conformation allows for the formation of supramolecular chains mediated by the sulfinyl-O and water molecules, see below. The benzene rings are splayed with respect to each other as seen in the value of the C1-C2-Se-C11 torsion angle of -27.7 (2) °; the dihedral angle formed between the rings is 51.66 (17) °.
In the crystal packing, the water molecules bridge sulfinyl-O atoms via O-H···O hydrogen bonds to form a linear supramolecular chain along the b axis, Fig. 2 and Table 1. Chains are stabilized by a series of C-H···O interactions, Table   1, and are held in place by C-H···π(aryl-Br) and C-Br···π(aryl-Se) interactions, Fig. 3 and Table 1.

Experimental
Following the procedure of Long (1946), a solution of potassium hydroxide (400 mg, 7.2 mmol) and ethanothiol (0.5 ml, 7.2 mmol) in ethanol (10 ml) was added to a solution of 2-bromo-4'-bromoacetophenone (2.0 g, 7.2 mmol) in ethanol, to give 2-ethylthio-4'-bromoacetophenone (1.6 g, yield = 86%). The product was isolated and oxidized with 12 ml of an aqueous solution of sodium periodate (0.5 M) in acetonitrile (16 ml), after Leonard & Johnson (1962), to give 2-ethylsulfinyl-4'-bromoacetophenone that was extracted with dichloromethane and dried over anhydrous magnesium sulfate. 2-Ethylsulfinyl-4'bromoacetophenone (730 mg, 2.6 mmol) was added drop-wise to a cooled (195 K) solution of diisopropylamine (0.4 ml, 2.6 mmol) and butyllithium (2.3 ml, 2.6 mmol) in THF (20 ml). After 20 minutes, phenylselenilbromide (610 mg, 2.6 mmol) dissolved in THF (10 ml) was added drop-wise to the enolate solution (Zoretic and Soja, 1976). After stirring for 3 h at 195 K, water (50 ml) was added at room temperature and extraction with chloroform was performed. The organic layer was dried over anhydrous magnesium sulfate. After evaporation of solvent, a crude solid was obtained. Purification through flash chromatography with a solution of hexane and ethyl acetate in a 1:1 ratio gave a mixture of the two possible diastereoisomers (500 mg, yield = 45%). One of the diastereoisomers was separated by recrystallization at low temperature (283 K) from chloroform. Suitable crystals for X-ray analysis were obtained by vapour diffusion of n-hexane into its chloroform solution  The H atoms were geometrically placed (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (C). Those of the water molecule were found in a difference map, fixed in those positions and refined with U iso (H) = 1.2U eq (O); see Table 1 for distances. Fig. 1. The molecular structure of (I) showing atom labelling scheme and displacement ellipsoids at the 35% probability level (arbitrary spheres for the H atoms).

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 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 Rfactors(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.