(E)-1,2-Bis(3-bromo-4-methylphenyl)ethene

In the structure of the title compound, C16H14Br2, the central C=C bond length is 1.329 (4) Å and the two benzene rings are approximately coplanar with the double bond, with twist angles of 7.5 (2) and 13.6 (2)°.

In the structure of the title compound, C 16 H 14 Br 2 , the central C C bond length is 1.329 (4) Å and the two benzene rings are approximately coplanar with the double bond, with twist angles of 7.5 (2) and 13.6 (2) .

S1. Comment
The title compound, (I) (Fig. 1), was prepared by a Ti catalyzed McMurray coupling (Mallory et al., 2001) with 99% E selectivity. The almost-planar molecules pack (Fig. 2) in slipped stacks with T-contacts typical for aromatic molecules.

S2. Experimental
At 273 K under N 2 , 0.18 ml (1.6 mmol) of TiCl 4 was stirred with 0.18 g (2.8 mmol) Zn dust in 25 ml of dry THF. To this mixture was added 0.25 g (1.3 mmol) of 3-bromo-4-methylbenzaldehyde and refluxed for 4 h before being quenched with 25 ml of 1.0 M HCl. After extracting with hexanes the organic phase was washed with brine solution and dried over MgSO 4 . Removal of solvent resulted in a white powder that was recrystallized from ethyl acetate to give 0.11 g (yield = 58%) of the desired product as colorless crystals.

S3. Refinement
The H-atoms were included in the refinements at geometrically idealized positions with C-H distances 0.95 and 0.98 Å for non-methyl and methyl type H-atoms, respectively; U iso values were 1.2U eq of the carrier atom or 1.5U eq for the nonmethyl and methyl groups, respectively.  A view of (I) plotted with displacement ellipsoids at 50% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.