(E)-4-Bromo-N-{(E)-3-[(4-bromo-2-methylphenyl)imino]butan-2-ylidene}-2-methylaniline

The title compound, C18H18Br2N2, is centrosymmetric with the mid-point of the central C—C bond of the butyl group located on an inversion center. The terminal benzene ring is approximately perpendicular to the central butyl plane [dihedral angle = 71.9 (8)°]. No hydrogen bonding or aromatic stacking is observed in the crystal.

The title compound, C 18 H 18 Br 2 N 2 , is centrosymmetric with the mid-point of the central C-C bond of the butyl group located on an inversion center. The terminal benzene ring is approximately perpendicular to the central butyl plane [dihedral angle = 71.9 (8) ]. No hydrogen bonding or aromatic stacking is observed in the crystal.

Experimental
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: XU5666). There is a considerable interest in the development of new late transition metal catalysts for the polymerization of αolefins since Brookhart discovered highly active α-diimine nickel catalysts (Johnson et al., 1995;Killian et al., 1996). It is well known that the ligand structure had significant influence on the product properties and polymerization activities (Popeney & Guan, 2010;Popeney et al., 2011;Yuan et al., 2005).
In this study, we designed and synthesized the title compound as a bidentate ligand, and its molecular structure was characterized by X-ray diffraction. In the solid state, the ligand exhibits a -1 symmetry. The single bond of 1,4-diazabutadiene fragment is (E)-configured. The dihedral angle between the benzene ring and 1,4-diazabutadiene plane is 71.9 (8)°, similar to that found in a related compound (Zhang et al., 2013). In the crystal packing, there is no hydrogenbond between the molecules.

Refinement
All hydrogen atoms were placed in calculated positions with C-H distances of 0.93 and 0.96 Å for aryl and methyl type H-atoms. They were included in the refinement in a riding model approximation, respectively. The H-atoms were assigned U iso = 1.2 times U eq of the aryl C atoms and 1.5 times U eq of the methyl C atoms.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  Molecular structure of the title compound, using 30% probability level ellipsoids. 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.