4,4,5,5-Tetramethyl-1,3,2λ5-dioxaphospholan-2-one

The five-membered ring in the title compound, C6H13O3P, exists in an envelope conformation with one of the ring C atoms at the flap position. The coordination geometry around the P atom is a distorted tetrahedron. The crystal structure is stabilized by several weak C—H⋯O and P—H⋯O hydrogen bonds, forming a three-dimensional network.

The five-membered ring in the title compound, C 6 H 13 O 3 P, exists in an envelope conformation with one of the ring C atoms at the flap position. The coordination geometry around the P atom is a distorted tetrahedron. The crystal structure is stabilized by several weak C-HÁ Á ÁO and P-HÁ Á ÁO hydrogen bonds, forming a three-dimensional network.

D-HÁ
Data collection: CrysAlis CCD (Oxford Diffraction, 2010); cell refinement: CrysAlis RED (Oxford Diffraction, 2010); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.  Carbon-carbon bond-forming catalytic reactions are very important fundamental processes in synthetic chemistry. Among them, one of the commonly recognized is the Heck reaction employing as the catalyst precursors palladium compounds with phosphorus ligands (Beletskaya & Cheprakov, 2000). Complexes incorporating in their structure 1,3,2-dioxaphospholane heterocyclic rings have been recently found to be efficient catalysts of the Heck reaction carried out under mild conditions (Skarżyńska et al., 2011). In this paper we report the synthesis and crystallization of tetramethyl dioxaphospholane, the title compound.

Structure Reports Online
The geometric parameters around the four-coordinate phosphorus atom ( Fig. 1) indicate a deformation of the ideal tetrahedron towards a trigonal pyramid. The O-P-O1 and O-P-O2 angles differ considerably from the ideal value of 109.5° and approach 120°, while O1-P-O2 is close to 90°. Such deformations might be explained by the effect of different substituents and bond types. Bond lengths P-O1, P-O2, P-O, and P-H are typical (Allen et al., 1987). The heterocyclic five-membered ring P/O1/C1/C2/O2 adopts an envelope conformation with the C1 atom deviating from the four-atom plane by about 0.55 Å.

Refinement
All H atoms were found in a difference Fourier map and refined isotropically. The measured C-H distances in methyl groups are in range 0.92 (2)-1.00 (2)Å and P-H bond length is 1.28 (2) Å. The highest residual peak and the deepest hole in the final difference map are located 0.77 and 0.76Å from the C1 and P atom, respectively.

Special details
Experimental. The crystal was placed in the cold stream of an open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100 K. Analytical numeric absorption correction was carried out with CrysAlis RED (Oxford Diffraction, 2010) using a multifaceted crystal model (Clark & Reid, 1995). 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.