(E)-2-(2,3-Dimethylanilino)-N′-(thiophen-2-ylmethylidene)benzohydrazide

In the title compound, C20H19N3OS, the central benzene ring makes dihedral angles of 45.36 (9) and 55.33 (9)° with the thiophene ring and the dimethyl-substituted benzene ring, respectively. The dihedral angle between the thiophene ring and dimethyl-substituted benzene ring is 83.60 (9)°. The thiophene ring and the benzene ring are twisted from the mean plane of the C(=O)—N—N=C bridge [maximum deviation = 0.0860 (13) Å], with dihedral angles of 23.86 (9) and 24.77 (8)°, respectively. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds to the same acceptor atom, forming sheets lying parallel to the bc plane. The crystal packing also features C—H⋯π interactions.


Abdel-Aziz Comment
In view of the importance of the chemistry and biological activity of diaryl amines (Reddy et al., 2010) and in continuation to our interest in the chemistry of hydrazones (Bhat et al., 2012a,b,c), we report herein the crystal structure of the title compound.

Experimental
The title compound was prepared by the reaction of thiophene-2-carbaldehyde (0.11 g, 1 mmol) and 2-[(2,3-dimethylphenylamine)]benzohydrazide (0.25 g, 1 mmol) in ethanol (25 ml). After stirring at room temperature for 3 h, the resulting mixture was concentrated under reduced pressure. The precipitate was washed with cold ethanol to afford the title compound. Yellow needles were recrystallized from ethanol solution by the slow evaporation of the solvent at room temperature after several days.

Refinement
The N-bound H atoms were located in a difference Fourier map and refined freely [N-H = 0.85 (3) and 0.89 (2) Å]. The remaining H atoms were positioned geometrically [C-H = 0.95 and 0.98 Å] and refined using a riding model with U iso (H) = 1.2 or 1.5U eq (C). A rotating group model was applied to the methyl groups. Two outliers, (302) and (312), were omitted in the final refinement.

Figure 1
The molecular structure of the title compound with 50% probability displacement ellipsoids. The dashed line represents the intramolecular N-H···O hydrogen bond.

Figure 2
The crystal packing of the title compound. The dashed lines represent the hydrogen bonds. For clarity sake, hydrogen atoms not involved in hydrogen bonding have been omitted.  (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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 > 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.