Diisopropyl [(4-methoxybenzamido)(p-tolyl)methyl]phosphonate

The asymmetric unit of the title compound, C22H30NO5P, contains two independent molecules in which the dihedral angles between the benzene rings are 82.0 (2) and 78.4 (2)°. In the crystal, each molecule forms an inversion dimer via a pair of N—H⋯O(=P) hydrogen bonds.

The asymmetric unit of the title compound, C 22 H 30 NO 5 P, contains two independent molecules in which the dihedral angles between the benzene rings are 82.0 (2) and 78.4 (2) . In the crystal, each molecule forms an inversion dimer via a pair of N-HÁ Á ÁO( P) hydrogen bonds.

Comment
The title compound, (I), was synthesized for a study of its antimicrobial activity against Bacillus subtilis. The hydroxyphosphonic acid derivative was found to have moderate antimicrobial activity (inhibition zone = 10 mm). The adjacent bonds P1-O3 and P1-O4 [mean 1.557 (8)

Experimental
Triphenylphosphine (0.39 g, 1.5 mmol) and hexachloroethane (0.39 g, 1.2 mmol) in dried 1,2-dichloroethane (15 ml) were reacted for 1 h in an ice bath. The resulting solution was added dropwise to a mixture of the hydrochloride of dialkyl α-aminotolylphosphonate (0.28 g, 1.0 mmol) and 4-methoxybenzoic acid (0.15 g, 1.0 mmol) in 1,2-dichloroethane (10 ml) and triethylamine (0.4 ml). After completion of the reaction, the solvent was removed to give the crude product, which was purified by recrystallization from hot ethanol. Single crystals of (I) suitable for X-ray analysis were obtained

Refinement
The H atoms were positioned geometrically (C-H = 0.93, 0.98 or 0.96 A for benzene, tertiary or methyl H atoms, respectively, and N-H = 0.86 Å) and were included in the refinement in the riding-model approximation. The displacement parameters of the methyl H atoms were set at 1.5 U eq of their parent atoms, while those of the other H atoms were set at 1.2 U eq (C,N).

Figure 1
The reaction scheme for the formation of the title compound.  The molecular structure of one independent molecule. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as spheres of arbitrary radii.

Figure 3
The molecular structure of the other independent molecule. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as spheres of arbitrary radii.  Part of the crystal structure with hydrogen bonds shown as dashed lines.

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.