Crystal structures of methyl 3,5-di-bromo-4-cyano-benzoate and methyl 3,5-di-bromo-4-iso-cyano-benzoate.

The title crystals, C(9)H(5)Br(2)NO(2), are the first reported 2,6-dihalophenyl cyanide-isocyanide pair that have neither three- nor two-dimensional isomorphism. Both crystals contain contacts between the carbonyl O atom and a Br atom. In the crystal of the cyanide, R(2)(2)(10) inversion dimers form based on C≡N⋯Br contacts, a common packing feature in this series of crystals. In the isocyanide, the corresponding N≡C⋯Br contacts are not observed. Instead, the iso-cyano C atom forms contacts with the meth-oxy C atom. RNC was refined as a two-component pseudo-merohedral twin.