Synthesis and crystal structures of (2)-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione and (2)-1,4-bis-(4-bromo-phen-yl)but-2-ene-1,4-dione.

The mol-ecular structure of (2)-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione [CHClO, ()] is composed of two -chlorophenyl rings, each bonded on opposite ends to a near planar 1,4- enedione moiety [-C(=O)-CH=CH-(C=O)-] [r.m.s. deviation = 0.003 (1) Å]. (2)-1,4-Bis(4-bromo-phen-yl)but-2-ene-1,4-dione [CHBrO, ()] has a similar structure to (), but with two -bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both mol-ecules sit on a center of inversion, thus ' = 0.5. The dihedral angles between the ring and the enedione group are 16.61 (8) and 15.58 (11)° for () and (), respectively. In the crystal, mol-ecules of () exhibit C-Cl⋯Cl type I inter-actions, whereas mol-ecules of () present C-Br⋯Br type II inter-actions. van der Waals-type inter-actions contribute to the packing of both mol-ecules, and the packing reveals face-to-face ring stacking with similar inter-planar distances of approximately 3.53 Å.