Conformational studies. Part IV. Crystal and molecular structure of the metastable form of N-(p-chlorobenzylidene)-p-chloroaniline, a planar anil

The title compound crystallises in the triclinic system with cell constants a = 5.986(2), b = 3.933(1), c = 12.342(2) Å, α = 87.38(3), β = 78.40(3), γ = 89.53(3)°, and Z = 1. The crystal and molecular structures were solved from 1458 intensities measured on a diffractometer, and refined anisotropically to R 0.062. The structure is disordered about a crystallographic inversion centre, which requires that the two aromatic rings must be parallel, the dihedral angles about the exocyclic bonds being equal but of opposite sign, in contrast to the structures of previously analysed benzylideneanilines. The metastable nature of the crystal is discussed in terms of the packing arrangement.