Diphenyl (isopropylamido)phosphate

The P atom in the title compound, C15H18NO3P, is in a distorted tetrahedral P(O)(O)2N environment; the bond angles at P are in the range 98.16 (6)–115.82 (6)°. In the crystal, adjacent molecules are linked via N—H⋯O=P hydrogen bonds into a chain running parallel to the b axis. The methyl groups are disordered over two sets of sites in a 0.677 (14):0.323 (14) ratio. The crystal studied was a non-merohedral twin with a refined minor component of 22.31 (4)%.

The P atom in the title compound, C 15 H 18 NO 3 P, is in a distorted tetrahedral P(O)(O) 2 N environment; the bond angles at P are in the range 98.16 (6)-115.82 (6) . In the crystal, adjacent molecules are linked via N-HÁ Á ÁO P hydrogen bonds into a chain running parallel to the b axis. The methyl groups are disordered over two sets of sites in a 0.677 (14):0.323 (14) ratio. The crystal studied was a nonmerohedral twin with a refined minor component of 22.31 (4)%.

Experimental
To a solution of [C 6 H 5 O] 2 P(O)Cl (2 mmol) in dry CH 3 CN (30 ml), a solution of isopropylamine (4 mmol) in the same solvent (5 ml) was added at ice bath temperature under stirring. After 4 h, the solvent was removed and the product was washed with distilled water and recrystallized from CH 3 CN/n-C 6 H 14 (4:1) at room temperature. The single crystals suitable for X-ray analysis were obtained from this solution after a few days at room temperature.

Refinement
The crystal sample was non-merohedrally twinned. Using data reduction software, a HKLF 5 file was produced for a two-component twin and used in the refinement. The fractional contribution of the minor twin component converged to 0.2231 (4). All carbon bound H atoms were placed at calculated positions and were refined as riding with their U iso set to either 1.2U eq or 1.5U eq (methyl) of the respective carrier atoms; in addition, the methyl H atoms were allowed to rotate about the C-C bond. Nitrogen bound H atom was located in a difference Fourier map and its position was refined while the N-H distance was fixed at 0.88 Å and the U iso set to 1.2U eq of N1. The disordered methyl groups were modeled over two sites while restraining their anisotropic displacement parameters to be approximately isotropic (ISOR). To maintain a correct hydrogen geometry, a dummy atom with zero occupancy was created and constrained to share the same site (EXYZ) and anisotropic displacement parameters (EADP) with a fully occupied carbon atom bound to N1.

Figure 1
The molecular structure of the title compound with ellipsoids shown at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii. The minor component of disordered part has been omitted for clarity and only one orientation is shown for the disordered part.  (6) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.

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