4-(4-Bromophenyl)-6-(4-chlorophenyl)pyrimidin-2-ylamine

The title compound, C16H11BrClN3, contains pairs of molecules lying about inversion centers linked by amino–pyrimidine N—H⋯N hydrogen bonds. The eight-membered rings thus formed are represented by the R 2 2(8) motif in graph-set notation. The second H atom of the amine group shows a rather weak interaction with two Br atoms, resulting in bifurcated N—H⋯(Br,Br) hydrogen bonds. The dihedral angles between the mean planes of the benzene rings and the mean plane of the heterocyclic ring are 8.98 (15) and 35.58 (10)°. The Br and Cl atoms show substitutional disorder, with site-occupancy factors of 0.599 (2) and 0.401 (2), respectively.


Comment
Pyrimidines are a class of biologically active compounds having utility in the pharmaceutical and the agrochemical industries. Compounds with the ring system show pharmacological activity such as antitumor (Gangjee et al., 1999;Grivsky et al., 1980), antiviral (Rao et al., 2003), anti-HIV (Malik et al., 2006, etc. In continuation of our research work (Bukhari et al., 2008), we have prepared several pyrimidines. In this article, we report the crystal structure of the title compound, (I).

Experimental
The title compound was synthesized by the procedure reported earlier (Bukhari et al., 2008). Crystals of (I) suitable for crystallographic analysis were grown by slow evaporation at 313 K from a solutuion of CHCl 3 (Yield 58%; m.p. 512-514 K).

Refinement
The Br and Cl atoms showed substitutional disorder with site occupancy factors refined for Br1 and Cl1 to 0.559 (2) and Br1' and Cl1' to 0.401 (2) values. C-Cl and C-Br distances were constrained using DFIX command in SHELXL97 (Sheldrick, 2008). Though all the H atoms could be distinguished in the difference Fourier map the H-atoms bonded to C-atoms were included at geometrically idealized positions and refined in riding-model approximation with the following constraints: C-H distances were set to 0.95 Å and U iso (H) = 1.2U eq (C). H-atoms bonded to N3 were taken from the difference map and were allowed to refine with U iso = 1.2 times U eq of the parent atom. The final difference map was free of any chemically significant features.

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 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.