(Z)-(1,2-Dichlorovinyl)diphenylphosphine oxide

The title compound, C14H11Cl2OP, was synthesized by the reaction of diphenylphosphine oxide with 1,2-dichloroethyne under CuI catalysis. The reaction provided the Z isomer regioselectively. Two O—P—C bond angles [114.3 (1) and 112.5 (1)°] are significantly larger than the C—P—C [107.7 (1), 105.6 (1) and 106.6 (1)°] and another O—P—C angle [109.5 (1)°], indicating significant distortion of the tetrahedral configuration of the P atom. In the crystal, molecules are linked by weak intermolecular C—H⋯O hydrogen bonds into centrosymmetric dimers, which are connected by further C—H⋯O interactions into chains along [101].

The title compound, C 14 H 11 Cl 2 OP, was synthesized by the reaction of diphenylphosphine oxide with 1,2-dichloroethyne under CuI catalysis. The reaction provided the Z isomer regioselectively. Two O-P-C bond angles [114.3 (1) and 112.5 (1) ] are significantly larger than the C-P-C [107.7 (1), 105.6 (1) and 106.6 (1) ] and another O-P-C angle [109.5 (1) ], indicating significant distortion of the tetrahedral configuration of the P atom. In the crystal, molecules are linked by weak intermolecular C-HÁ Á ÁO hydrogen bonds into centrosymmetric dimers, which are connected by further C-HÁ Á ÁO interactions into chains along [101].

Comment
Alkenylphosphine oxides have attracted much attention because they are used as biologically active compounds (Haynes et al., 1989;Haynes et al., 1991;Shi et al., 2000), and are the key intermediates for preparation of some palladium catalysts (Inoue et al.,2002). Nucleophiles, such as amines (Rahman et al., 2000;Rahman et al., 2004), phosphines (Barbaro et al., 2002;Alajarin et al., 2004;Han & Zhao, 2005) and carbanion species readily add to the olefinic bond in alkenylphosphine oxides to give useful bifunctional adducts. In order to further confirm stereostructure and structure-activity relationship of alkenylphosphine oxides, we performed the synthesis of the title compound by addition reaction of the diphenylphosphine oxide with 1,2-dichloroethyne under catalysis of commercially available CuI at room temperature. The reaction provided (Z)-(1,2-dichlorovinyl)diphenylphosphine oxide regioselectively. The study of the crystal structure of the title compound was commenced to establish its structural features that can be helpful for its practical applications. In the title molecule ( Fig. 1

Experimental
To a stirred solution of 1,2-dichloroethyne (1.88 g, 20 mmol) in anhydrous ether (40 ml), a solution of diphenylphosphine oxide (2.23g, 12mmol) in ether (10 ml) was added dropwise in the presence of CuI (0.229g, 1.2 mmol) at room temperature in nitrogen atmosphere for 4h. After completion of the reaction as indicated by thin-layer chromatography, the mixture was filtered and rinsed with ethyl acetate. The organic layer was washed with brine and dried over MgSO 4 . The title product was obtained by crystallization as colourless solid. The product obtained was purified by flash chromatograghy. Single crystals of the title compound suitable for single-crystal X-ray analysis were obtained by recrystallization from ether.

Refinement
The H atoms were positioned geometrically and refined using a riding model with C-H = 0.93-0.98 Å and with U iso (H)= 1.2U eq (C).
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.

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 > 2sigma(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.