Crystal structure of 1,2-bis-[(2-tert-butyl-phen-yl)imino]-ethane

The whole molecule of the title compound, C22H28N2, (I), is generated by inversion symmetry. The mol-ecule is rather similar to that of 2,3-bis-[(2-tert-butyl-phen-yl)imino]-butane, (II), a di-imine ligand comprising similar structural features [Ferreira et al. (2006 ▶). Acta Cryst. E62, o4282-o4284]. Both ligands crystallize with the -N=C(R)-C(R)=N- group around an inversion centre, in a trans configuration. Comparing the two structures, it may be noted that the independent planar groups in both mol-ecules [the central link, -N=C(R)-C(R)=N-, and the terminal aromatic ring] subtend an angle of 69.6 (1)° in (II) and 49.4 (2)° in (I). Ferreira and co-workers proposed that such angle deviation may be ascribed to the presence of two non-classical intra-molecular hydrogen bonds and steric factors. In fact, in (I), similar non-classical hydrogen bonds are observed, and the larger angular deviation in (II) may be assigned to the presence of methyl groups in the di-imino fragment, which can cause steric hindrance due to the presence of bulky tert-butyl substituents in the aromatic rings. The C=N bond lengths are similar in both compounds and agree with comonly accepted values.