Diphenyl[2-(phenylsulfonyl)propan-2-yl]-λ5-phosphanethione

The title compound, C21H21O2PS2, was obtained from the corresponding dilithio methandiide by treatment with iodomethane. The bond lengths and angles deviate considerably from those in the dimetallated compound. These differences are most pronounced in the PCS backbone. While the title compound features C—P and C—S distances of 1.9082 (17) and 1.8348 (17) Å, respectively, the dianion showed C—Pav distances shortened by 11% [1.710 (4) Å] and C—S distances shortened by 12% [1.614 (3) Å]. Additionally, the P—C—S angle experiences a contraction by methylation of the dianion from 121.4 (2) to 111.96 (9)° in the title compound.

VHG thanks the Deutsche Forschungsgemeinschaft, the Alexander von Humboldt Foundation and the Fonds der Chemischen Industrie for financial support as well as Professor Dr Holger Braunschweig for generous support.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5837).

Comment
Methylene compounds with two anion stabilizing substituents, such as phosphonium or sulfonyl moieties, have become interesting reagents due to their possible transformation into the corresponding methandiide by double deprotonation. (Kasani et al., 1999;Ong et al., 1999;Cantat et al., 2006) These geminal dianions have caught special attention because of their unique electronic properties and structures, which enabled the isolation of a planar four-coordinate carbon atom (Cooper et al., 2010). Additionally, these dianionic species have proven to be efficient ligand systems for the construction of novel carbene complexes, which differ from the known Fischer and Schrock-type complexes. Thereby, a huge variety of different compounds incorporating early and late transition metals as well as lanthanoids and actinoids have been reported (Cavell et al., 2001;Cantat et al., 2008;Harder, 2011).
As part of our studies on dilithio methandiides we developed a new methylene coumpound with both, a thiophosphinoyl and a sulfonyl moiety (Gessner, 2011;Gessner et al., 2012). This compound is easily converted into its dianionic congener, which features strongly distorted geometries of the metallated carbon atoms, which can be explained by a novel bonding mode of a sp 2 -hybridized carbon with the two lithium atoms. Treatment of the dilithio methandiide with iodomethane furnished the dimethylated titel compound. The bond lengths and angles are comparable to the protonated analogue, but deviate considerably from the dimetallated compound. These differences are most pronounced in the PCS backbone. While the title compound features C-P and C-S distances of 1.908 (2) and 1.835 (2) Å, respectively, the dianion showed C-P av distances shortened by 11% [1.710 (4) Å] and C-S distances shortened by 12% [1.614 (3) Å] (Gessner et al., 2012). Additionally, the P-C-S angle experiences a contraction by methylation of the dianion from 121.4 (2)° to 112.0 (1)° in the title compound. This is the result of the re-hybridization from a sp 2 -hybridized carbon in the methandiide to an sp 3 -hybridized carbon in the title compound.
Experimental 284 mg (2.00 mmol) iodomethane were added to a suspension of 405 mg (0.20 mmol, equates to 0.81 mmol per molecule) of the corresponding dilithio methandiide in 20 ml THF at room temperature. After stirring for 4 h the mixture was treated with 20 ml of an aqueous ammonia solution (25%) and the mixture extracted with diethyl ether. Drying over sodium sulfate and removal of the solvent in vacuo afforded the crude product as orange oil. The product was obtained as colorless solid after purification by flash chromatography (eluent: pentane/diethyl ether= 1:1, R F = 0.33) on silica (285 mg, 0.71 mmol; 88%). Single crystals were grown by slow evaporation of a solution of the title compound in THF. 1

Refinement
H atoms were located in a difference map and refined as riding with C-H ranging from 0.95Å to 0.98Å and U(H) set to 1.2U eq (C) or 1.5U eq (C methyl ).

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Diphenyl[2-(phenylsulfonyl)propan-2-yl]-λ 5 -phosphanethione
Crystal data C 21 H 21 O 2 PS 2 M r = 400.47 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 8.2137 (7)  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.