2,4,6-Triphenyl-N-{(3E)-3-[(2,4,6-triphenylphenyl)imino]butan-2-ylidene}aniline

The title molecule is disposed about a centre of inversion and the conformation about the imine bond is E. The terminal benzene ring is approximately perpendicular to the central 1,4-diazabutadiene mean plane, forming a dihedral angle of 81.2 (3)°.


Structure description
The seminal studies by Brookhart and co-workers leading to the discovery of cationicdiimine-based Ni and Pd catalysts marked the start of a new era in olefin polymerization studies (Killian et al., 1996). Branched polyolefins are generally produced using these catalysed ethylene polymerizations through a characteristic chain-walking process (Wang & Chen, 2019). More importantly, these -diimine Ni and Pd catalysts are able to copolymerize olefins with polar co-monomers to afford co-polymers containing functional groups without the pre-protection of the polar groups (Chen et al., 2018). For the synthesis of the -diimine molecules and background to the applications of the olefin polymerization catalysts ligated by -diimine, see: Wang et al. (2016Wang et al. ( , 2018Wang et al. ( , 2019. In this study, we designed and synthesized the title compound (Fig. 1) as a potential bidentate ligand, and its molecular structure was characterized by X-ray diffraction. In the solid state, the molecule exhibits C i symmetry, being disposed about a centre of inversion. The single bond of the 1,4-diazabutadiene fragment [1.491 (4) Å ] has an antidisposition and the imine bonds [1.268 (3) Å ] are E-configured. The dihedral angle between the pendent benzene ring and the 1,4-diazabutadiene least-squares plane is 81.2 (3) , consistent with an almost perpendicular relationship. In the crystal, C-HÁ Á Á, Table 1, andinteractions are noted. For the latter, the closest approach of 4.021 (5) Å data reports occurs between centrosymmetrically related (C13-C18)phenyl rings with the off-set distance being 1.86 Å ; symmetry operation Àx, 1 À y, 1 À z.

Synthesis and crystallization
After the protection of the amino group by acetic acid, the aniline was brominated. The Suzuki coupling reaction of the aniline and phenylboronic acid catalysed by a Pd catalyst in PEG-400 /H 2 O led to the corresponding triphenyl-substituted aniline (Fig. 2). The title compound was prepared by the condensation of two equivalents of the appropriate aniline with one equivalent of 2,3-butanedione, in the presence of formic acid or p-toluenesulfonic acid, as a catalyst at 81% yield.

Figure 1
Molecular structure of the title compound showing the atom-labelling scheme and displacement ellipsoids at the 30% probability level. Unlabelled atoms are related by the symmetry operation À x, 2 À y, 1 À z. Table 1 Hydrogen-bond geometry (Å , ).
Cg1 is the centroid of the (C19-C24) phenyl ring.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.16 e Å −3 Δρ min = −0.19 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

data-2
IUCrData (2020). 5, x200531 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 > 2sigma(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. 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 Uiso = 1.2 times Ueq of the aryl C atoms and 1.5 times Ueq of the methyl C atoms.