Experimental

R factor = 0.065; wR factor = 0.145; data-to-parameter ratio = 15.2. The title compound, C16H8Cl4O2, crystallizes with two independent molecules in the asymmetric unit. Both mol-ecules have a Z conformation around the central double bond and they show significantly different C—C—C—O torsion angles between the aromatic ring and the carbonyl group [30.1 (7) and 3.9 (7) in one molecule and 23.5 (7) and 9.3 (8) in the other]. The crystal packing shows short halogen Cl O [3.003 (5) and 3.246 (4) Å] and Cl Cl [3.452 (2) Å] contacts and aromatic C—H Cl and C—H O interactions link the molecules, resulting in chains propogating along [100]. The crystal structure also features – stacking interactions between aromatic units of the two independent molecules, with a centroid–centroid distance of 3.9264 (6) Å. Related literature For general background and details of the synthesis, see: Clar