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

Abstract

The mol-ecular structure of (2E)-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione [C₁₆H₁₀Cl₂O₂, (1)] is composed of two p-chlorophenyl rings, each bonded on opposite ends to a near planar 1,4-trans enedione moiety [-C(=O)-CH=CH-(C=O)-] [r.m.s. deviation = 0.003 (1) Å]. (2E)-1,4-Bis(4-bromo-phen-yl)but-2-ene-1,4-dione [C₁₆H₁₀Br₂O₂, (2)] has a similar structure to (1), but with two p-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 Z' = 0.5. The dihedral angles between the ring and the enedione group are 16.61 (8) and 15.58 (11)° for (1) and (2), respectively. In the crystal, mol-ecules of (1) exhibit C-Cl⋯Cl type I inter-actions, whereas mol-ecules of (2) 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.

Keywords: 1,4-enedione moiety; NMR; bis-halo-enedione; crystal structure; synthesis.

Figure 1

Mol­ecular conformation and atom-numbering scheme of (1) (top) and (2) (bottom). The non-labeled atoms are generated by symmetry operation (−x, 1 − y, 1 − z) for (1) and (1 − x, −y,1 − z) for (2). Non-hydrogen atoms are shown as 50% probability displacement ellipsoids.

Figure 2

Superimposition of structure (1) (green) onto the inverted structure of (2) (red). Only the asymmetric unit of (1) is presented for clarity.

Figure 3

Crystal packing of (1) along the vicinity of the a axis. Dashed lines depict Cl1⋯Cl1ⁱ and O1⋯H3ⁱⁱ inter­actions [symmetry codes: (i) 2 − x, −y, −z; (ii) −1 + x, 1 + y, z].

Figure 4

Mol­ecular conformations of (1) and (2) viewed along the b and c axes, respectively, showing type I and II halogen inter­actions, centroid-to-centroid distances, and short intra­molecular H⋯H inter­actions.

Figure 5

Crystal packing of (2) along the b axis. Dashed blue lines represent bifurcated Br1⋯Br1^iv,v inter­actions [symmetry codes: (iv) −x, − + y,  − z; (v) −x,  + y,  − z] and trifurcated interactions involving the O1 atoms.