4-Bromo-N-(diisopropoxyphosphoryl)benzamide

In the title compound, C13H19BrNO4P, the crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds between the phosphoryl O atom and the amide N atom which link the molecules into centrosymmetric dimers. These dimers are further packed into stacks along the c axis by intermolecular C—H⋯O and C—H⋯π interactions.

In the title compound, C 13 H 19 BrNO 4 P, the crystal structure is stabilized by intermolecular N-HÁ Á ÁO hydrogen bonds between the phosphoryl O atom and the amide N atom which link the molecules into centrosymmetric dimers. These dimers are further packed into stacks along the c axis by intermolecular C-HÁ Á ÁO and C-HÁ Á Á interactions.

Comment
The chemistry of phosphine derivatives of urea and thiourea was first studied during the 1960 s (Birdsall et al., 1999). Subsequently, related bidentate organophosphorus ligand systems were developed to form R 1 C(X)NHPR 2 and their derivatives (Safin et al., 2006). Different R 1 C(X)NHP(Y)R 2 R 3 (R 1 = RNH or NZ 2 with Z = H, alkyl or aryl; R 2 , R 3 = alkyl, aryl, alkoxy or aryloxy; X, Y = O, S, Se) have been reported (Crespo et al., 2004). These types of ligands have recently been used successfully as ionophores for the transport and extraction of a number of metal ions (Luckay et al., 2009a(Luckay et al., , 2009b. Here we report the crystal structure of the title compound (I) (Fig. 1).
The crystal structure is stabilized by intermolecular N-H···O hydrogen bonds between the phosphoryl O atom and the amide N atom which link the molecules into centrosymmetric dimers (Table 1 and Fig. 2). These dimers are further packed into stacks along the c axis by intermolecular C-H···O and C-H···π interactions; the first between the benzene H atom and the oxygen of the C═O unit, with a C3-H3···O4 ii , the second between the benzene H atom and the oxygen of the P═O unit, with a C6-H6···O1 i , the third between the methyl H atom of the isopropyl group and the benzene ring, with a C16-H16C···Cg iii (Cg is the centroid of the C1-C6 benzene ring), respectively (Table 1 and Fig. 2).
Experimental 4-bromo-N-(diisopropoxyphosphoryl)benzthioamide was prepared according to the procedure of Safin et al. (2009). This ligand and one equivalent of copper(I) iodide was dissolved in acetone and heated to 50 °C for 2 hours. The colourless powder obtained was dissolved in a minimal quantity of THF and allowed to slowly evaporate. After 6 days, colourless needles were deposited. The hydrolysis of the thione group group was most likely caused by the presence of moisture in the solvents as well as the presence of the Cu + ion.

Refinement
All H atoms were positioned geometrically (C-H = 0.95, 1.00 and 0.98 Å for aromatic CH, alkyl CH and CH 3 groups, respectively; N-H = 0.88 Å) and constrained to ride on their parent atoms. U iso (H) values were set at 1.2 times U eq (C,N) except for methyl groups where U iso (H) was set at 1.5 times U eq (C).
The largest residual electron density peak of 1.29 e Å -3 is located 0.93 Å next to Br1.

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.