Crystal structures of 2,6-dibromo-4-methylbenzonitrile and 2,6-dibromo-4-methylphenyl isocyanide

In the title crystals, C 8 H 5 Br 2 N, which are isomorphous, the steric bulk of the methyl group causes neighboring molecules to become mutually inclined. This prevents the formation of planar or nearly planar sheets, which were observed in the trichloro and tribromo analogs. Instead of CN/NCBr contacts, tetrameric BrBr contacts are observed. These contacts form tetragonally puckered sheets parallel to (001). The CN/NC and methyl groups are grouped at the peaks and troughs. Both molecules lie across crystallographic mirror planes; thus, the methyl H atoms are disordered over two sets of sites with equal occupancy. The title nitrile is a redetermination. The refinement converged at R[F 2 > 2σ(F 2)] = 0.020, whereas the original determination [Gleason & Britton, (1976). Cryst. Struct. Commun. 5, 229-232] had R = 0.112.