N-(Diphenylvinylidene)-2,6-diisopropylaniline

The title compound, C26H27N, was prepared by the elimination of water from N-(2,6-diisopropylphenyl)-2,2-diphenylacetamide. The angle at the central C atom of the cumulene measures 172.5 (4)°. Molecules are connected into infinite chains by intermolecular C—H⋯N interactions.

The title compound, C 26 H 27 N, was prepared by the elimination of water from N-(2,6-diisopropylphenyl)-2,2-diphenylacetamide. The angle at the central C atom of the cumulene measures 172.5 (4) . Molecules are connected into infinite chains by intermolecular C-HÁ Á ÁN interactions.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NC2125).

Comment
In the course of a study on the organometallic and catalytic chemistry of aromatic imines (Imhof, 1997a,b) we became interested in the reactivity of the vinylogous keteneimines. The latter are prepared by the elimination of water from the corresponding acetamides by P 2 O 5 in anhydrous pyridine (Stevens & Singhal, 1964).
As expected the molecular structure of the title compound shows an almost linear cumulene system with an angle of 172.5 (4)° at the central C atom. The bonds C1-C2 and C2-N1 show bond lengths of 1.332 (5) and 1.213 (4) Å, respectively. The dihedral angle between the C1-C8-C14 plane and the aromatic substituent at the imine N atom measures to 52.4 (7)° which means that the substituents at the cumulene system do not show the expected orthogonal arrangement. This  et al., 1984) as it is also observed for the title compound. The lone pair at nitrogen is involved in a weak intramolecular hydrogen bond (Desiraju & Steiner, 1999) interaction towards H5 leading to the formation of infinite chains.

Experimental
The title compound was prepared following a literature method (Stevens & Singhal, 1964). A sample of 2 g (5.4 mmol) N-(2,6-Diisopropyl-phenyl)-2,2-diphenyl-acetamide was dissolved in 50 ml of anhydrous pyridine. To this solution 5 g P 2 O 5 were added and the mixture was refluxed for 7 h. After cooling the solution was filtered and pyridine was evaporated resulting in a red oily residue. The oil was transferred to a short chromatography column and light petroleum (b.p. 40-60°C) was used to elute a yellow solution of the title compound. Concentration of the solution and cooling to 4°C led to the formation of crystalline material from which the crystal for the structure analysis described herein was collected (yield: 1.56 g, 82%

Refinement
H atoms were positioned with idealized geometry at distances of 0.95 Å for aromatic C-H functions, 1.00 Å for aliphatic C-H bonds and 0.98 Å for methyl groups and were refined riding on their parent atoms with isotropic thermal parameters supplementary materials sup-2 of 1.2 times the corresponding values of their parent atoms. In the absence of significant anomalous dispersion effects, Friedel pairs were averaged. Fig. 1. The molecular structure of the title compound, presenting the labelling scheme and 40% probability displacement ellipsoids for non-H atoms.