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Chemistry
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4,6-Dibromo-N-{3-[(4,6-dibromo-2,3-dimethylphenyl)imino]butan-2-ylidene}-2,3-dimethylaniline

The title compound, C20H20Br4N2, is a product of the condensation reaction of 4,6-dibromo-2,3-dimethylaniline and butane-2,3-dione. The molecule has a center of symmetry at the mid-point of the central C—C bond. The dihedral angle between the benzene ring and the 1,4-diazabutadiene plane is 78.3 (2)°. Niether hydrogen bonding nor aromatic stacking is observed in the crystal structure.

The title compound, C 20 H 20 Br 4 N 2 , is a product of the condensation reaction of 4,6-dibromo-2,3-dimethylaniline and butane-2,3-dione. The molecule has a center of symmetry at the mid-point of the central C-C bond. The dihedral angle between the benzene ring and the 1,4-diazabutadiene plane is 78.3 (2) . Niether hydrogen bonding nor aromatic stacking is observed in the crystal structure.

Comment
Since Brookhart and co-workers discovered nickel and palladium(II) aryl-substituted α-diimine catalysts for olefin polymerization (Johnson et al., 1995), late transition metal catalysis has attracted increasing attention due to their high functional group tolerance and their ability to produce branched or dendritic polymer Sun et al., 2012;Popeney et al., 2012;Shi et al., 2012;Zhang & Ye, 2012;Killian et al., 1996;Yuan et al., 2005;2011). In this study, we designed and synthesized the title compound as abidentate ligand (Fig. 1).
The title molecule placed in center of symmetry (middle of C6-C6 i bond). The dihedral angle between the benzene ring and 1,4-diazabutadiene plane is 78.3 (2)°. Niether hydrogen bonding nor aromatic stacking are observed in the crystal structure.

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

Figure 2
A condensation reaction of 2,3-butanedione and 4,6-dibromo-2,3-dimethylaniline. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.70 e Å −3 Δρ min = −1.04 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.