2,6-Dichloroaniline–4-(2,6-dichloroanilino)pent-3-en-2-one (1/2)

The asymmetric unit of the title compound, C6H5Cl2N·2C11H11Cl2NO, is composed of one molecule of an enamino–ketone [i.e. –(2,6-dichlorophenylamino)pent-3-en-2-one] and half a molecule of 2,6-dichloroaniline, the whole molecule of the latter component being generated by twofold rotational symmetry. In this latter molecule, there are two intramolecular N—H⋯Cl contacts. In the enamino–ketone molecule, there is an N—H⋯O hydrogen bond of moderate strength, and the dihedral angle between the benzene ring and pentanone fragment [C—C(—N)=C—C(=O)—C; planar within 0.005 (1) Å] is 81.85 (7)°. In the crystal, two molecules of the enamino–ketone are bridged by a molecule of 2,6-dichloroaniline via N—H⋯O hydrogen bonds of moderate strength. There are also π–π interactions present, involving the benzene rings of inversion-related enamino–ketone molecules [centroid–centroid distance = 3.724 (4) Å].


Comment
The β-diketone compound AcacH (acetylacetone; or acetylacetonato if it is coordinated) has been studied extensively, and a large number of its derivatives have been synthesized up to date. One of these derivative types is known as enamino-ketones, which contain an unsaturated C═C bond as well as nitrogen and oxygen atoms. enamino-ketones are of interest in various fields including liquid crystals (Pyżuk et al., 1993), fluorescence studies (Xia et al., 2008), medicine (Tan et al., 2008) and catalysis (Roodt & Steyn, 2000;Brink et al., 2010).
The 2,6-dichloroaniline molecule is located on a two-fold rotation axis. The pertinent two-fold axis passes through atoms N21, C211, C214 and H214. The molecule thus has symmetry of point group 2. The dihedral angle between the phenyl ring and the mean plane of the pentanone fragment [C1-C2(-N11)═ C3-C4(═O12)-C5; maximum deviation 0.005 (1) Å for atom C4] in the title enamino-ketone, where the substituents are situated in the ortho position on the phenyl ring, is 81.85 (7) °. This angle is dependent on the position of the substituent on the phenyl ring, for example compounds with para substituents usually display smaller dihedral angles (Venter et al., 2010).
As expected the bond distances in the title enamino-ketone differ significantly from the respective distances in compounds where the enamino-ketone is coordinated to rhodium Damoense et al., 1994; see Table 2), but they display similar bond distances to those observed in analogous enamino-ketones (Venter et al., 2010;Venter, Brink et al., 2012). The difference between the C2-C3 bond distance [1.376 (2) Å] and the C3-C4 bond distance [1.457 (3) °] indicates an unsaturated C2═C3 bond in the pentenone backbone, which is consistent with the definition of an enamino-ketone. The N11···O12 distance is longer by ca. 0.2 Å upon coordination when comparing the title structure and selected compounds (II) and (III) with complexes (IV) and (V), as indicated in Table 2. compound is stable in air and light over a period of several months.

Refinement
All the hydrogen atoms were identified in a difference electron density map. The NH and NH 2 H atoms were refined with U iso (H) = 1.2U eq (N). The C-bound H atoms were placed into the idealized positions and constrained to ride on their parent atoms: C-H = 0.95 and 0.98 Å for CH and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C) where k = 1.5 for CH 3 H atoms, and = 1.2 for other H atoms. The methyl groups were refined as rigid rotors in order to fit to the electron density.

Computing details
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: WinGX (Farrugia, 2012).  A view of the unit cell along the b axis of the crystal structure of the title compound, illustrating the intra-and intermolecular N-H···O hydrogen bonds (dashed yellow lines). 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 > 2σ(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.