(Z)-N-[(Z)-3-(2,5-Dimethylphenylimino)butan-2-ylidene]-2,5-dimethylaniline

The asymmetric unit of the title compound, C20H24N2, contains one half-molecule, with the single C—C bond of the 1,4-diazabutadiene fragment situated on a centre of symmetry. The benzene rings are inclined to the 1,4-diazabutadiene mean plane by 59.5 (1)°.

The asymmetric unit of the title compound, C 20 H 24 N 2 , contains one half-molecule, with the single C-C bond of the 1,4-diazabutadiene fragment situated on a centre of symmetry. The benzene rings are inclined to the 1,4-diazabutadiene mean plane by 59.5 (1) .

Comment
In a continuation of our crystallographic study of the compounds used as α-diimine ligands for Ni II -α-diimine olefin polymerization catalysts (Yuan et al., 2012), we present here the crystal structure of the title compound (I).

Experimental
Formic acid (1 ml) was added to a stirred solution of 2,3-butanedione (0.052 g, 0.6 mmol) and 2,5-dimethylaniline (0.145 g, 1.2 mmol) in methanol (30 ml). The mixture was refluxed for 24 h, and then the solvent was removed. The residue was purified by chromatography on silica gel with petroleum ether/ethyl ester (v/v = 20:1). The crude product was recrystallized from ethanol/dichloromethane (v/v = 8:1). The pure product was washed and dried in vacuo to give a fine yellow powder. Yield: 0.143 g (82%). Crystals suitable for X-ray structure determination were grown from a solution of the title compound in a mixture of cyclohexane/dichloromethane (v/v = 1:2).

Refinement
All H atoms were placed in calculated positions (C-H = 0.93-0.96 Å) and included in the refinement in a riding-model approximation, with U iso (H) = 1.2-1.5U eq (C).

Computing details
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).   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.