N,N′-[(2E,3E)-Butane-2,3-diylidene]bis[4-fluoro-2-(1-phenylethyl)aniline]

The title molecule, C32H30F2N2, a product of the condensation reaction of butane-2,3-dione and 4-fluoro-2-(1-phenylethyl)aniline, is located about an inversion centre. In the asymmetric unit, the dihedral angle between the planes of the benzene and phenyl rings is 84.27 (5)°. Neither hydrogen bonding nor aromatic stacking is observed in the crystal structure.

We gratefully acknowledge the Natural Science Foundation of China (21261021), the Program for Changjiang Scholars and Innovative Research Teams in Universities of the Ministry of Education of China (IRT1177), the Natural Science Foundation of Gansu Province (1208RJZA140) and the NWNU Young Teachers Reseach Improving Program (NWNU-LKQN-10-11) for financial support.

Comment
An α-diimine ligands with different electronic property, rigidity and steric hindrance has been widely synthesized due to their significant applications in catalysis, coordination chemistry and carbene chemistry (Grasa et al., 2001;Williams et al., 2008;Hanhan et al., 2012;Partyka, 2011;Yuan et al., 2012). As part of our research efforts focused on developing ligands and organic catalysts, a novel series of imine derivatives were synthesized. Herein, we report the preparation and crystal structure of the title compound (Fig. 1).
The title molecule, is a symmetrical structure, and the central butanediimine moiety (N═C(Me)-C(Me)═N) is planar.
The dihedral angles between the benzene ring C8-C13 and benzene ring C1-C6 is 84.27 (5)°. The molecular dimensions in the title compound agree very well with the corresponding one reported in a few closely related compounds (Zou et al., 2008;Lohr et al. 2011).

Refinement
All hydrogen atoms were placed in calculated positions with C-H distances of 0.93Å, 0.96Å and 0.98Å for aryl, methyl and methine H atoms. They were included in the refinement in a riding model approximation, respectively with U iso = 1.2U eq (C) for aryl and methine H, and U iso = 1.5U eq (C) for methyl H.

Figure 2
A condensation reaction of 2,3-butanedione and 4-fluoro-2-(1-phenylethyl)aniline. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.15 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0100 (10) 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.