Dimethyl(2-oxo-2-phenylethyl)sulfanium bromide

Single crystals of the title compound, C10H13OS+·Br−, were obtained from ethyl acetate/ethyl ether after reaction of acetophenone with hydrobromic acid and dimethylsulfoxide. The carbonyl group is almost coplanar with the neighbouring phenyl ring [O—C—C—C = 178.9 (2)°]. The sulfanium group shows a trigonal–pyramidal geometry at the S atom. The crystal structure is stabilized by C—H⋯Br hydrogen-bonding interactions. Weak π–π interactions link adjacent phenyl rings [centroid–centroid distance = 3.946 (2) Å].

Single crystals of the title compound, C 10 H 13 OS + ÁBr À , were obtained from ethyl acetate/ethyl ether after reaction of acetophenone with hydrobromic acid and dimethylsulfoxide. The carbonyl group is almost coplanar with the neighbouring phenyl ring [O-C-C-C = 178.9 (2) ]. The sulfanium group shows a trigonal-pyramidal geometry at the S atom. The crystal structure is stabilized by C-HÁ Á ÁBr hydrogen-bonding interactions. Weakinteractions link adjacent phenyl rings [centroid-centroid distance = 3.946 (2) Å ].

Experimental
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2010); software used to prepare material for publication: publCIF (Westrip, 2010 Comment sulphanium salts, characterized by a low sulphur valence and relatively unstable carbon-sulphur bonds, have found a broad practical application in organic chemistry. For example, dimethylphenacylsulphanium salts have been used for synthesis of a new class of photoinitiators for cationic polymerization (Crivello et al., 2000) as well as of novel fluorophores (Hirano et al., 2001). In the crystal structure of the title complex ( Fig. 1), the phenyl ring is coplanar with the carbonyl group. The sulphanium group shows a trigonal-pyramidal geometry. All the bond lengths and bond angles are within the normal range (Dossena et al., 1983;Svensson et al., 1996).
Experimental Acetophenone (0.05 mol) was dissolved in a mixture of 48% (w%) aqueous hydrobromic acid (20 ml) and dimethylsulfoxide (40 ml). This solution was heated under reflux for 5 h to afford the title compound. The mixture was extracted three times, each time with 25 ml of ethyl acetate. Ethyl ether (15 ml) was added to the combined organic extracts. The solution was allowed to stand overnight. After filtration and washing with ethyl ether, colourless needle-shaped crystals were obtained.
The crystals were as long as 13 mm being thick of about 0.4 mm.

Refinement
All the hydrogens could have been discerned in the difference electron map. However, the hydrogens were situated into the idealized postions and treated in the riding mode approximation. The used constraints were as follows: C-H = 0.93 (aryl C), C-H = 0.97 (methylene C), C-H = 0.96 Å (methyl C). U iso (H) = 1.2U eq (C aryl /C methylene ), U iso (H) = 1.5U eq (C methyl ). Fig. 1. The molecular structure of the title compound with the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.

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

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