Dimethyl 2-[2-(2,4,6-trichlorophenyl)hydrazin-1-ylidene]butanedioate

In the title compound, C12H11Cl3N2O4, the dihedral angle between the aromatic ring and the hydrazine (NH—N=C) grouping is 52.2 (3)°. The butanedioate groups exhibit planar conformations. An intramolecular N—H⋯O hydrogen bond links the N—H group of the hydrazine to one of the methoxy groups of the butanedioate moiety. In the crystal, molecules are linked by C—H⋯O hydrogen bonds and π–π interactions are also observed [centroid–centroid separation = 3.535 (1) Å].

In the title compound, C 12 H 11 Cl 3 N 2 O 4 , the dihedral angle between the aromatic ring and the hydrazine (NH-N C) grouping is 52.2 (3) . The butanedioate groups exhibit planar conformations. An intramolecular N-HÁ Á ÁO hydrogen bond links the N-H group of the hydrazine to one of the methoxy groups of the butanedioate moiety. In the crystal, molecules are linked by C-HÁ Á ÁO hydrogen bonds andinteractions are also observed [centroid-centroid separation = 3.535 (1) Å ].

Comment
It has been reported in the literature that halo substituted derivatives possess significant pharmacological activity (Kees et al., 1996). Also the title compound can be used as an intermediate for the synthesis of pyrazoles (Palacios et al., 1999).
In the title compound, C 12 H 11 C 13 N 2 O 4 , the trichlorophenyl ring is planar (r.m.s. deviation 0.018 Å); the largest deviation from the mean plane is 0.02 (3) Å for atom C1. The bond distances in the title compound are comparable to those observed in the closely related structure (E)-benzaldehyde (2,4,6-trichlorophenyl) hydrazone (Huang et al., 2011). The C1 -N10-N11-C12 torsion angle of the atoms joining the trichlorophenyl ring and the butanedioate group is 175.9 (3).

Experimental
The title compound was prepared by refluxing a mixture of trichlorophenyl hydrazine (0.01 mol) and dimethylacetylene dicarboxylate (0.01 mol) in a 10 ml toluene solution for 4 h. The completion of the reaction was monitored by thin layer chromatography. After completion the solvent was evaporated under reduced pressure and the white solid obtained was recrystallized from ethanol.

Refinement
Atom H10 attached to N10 was located in a difference map and refined isotropically. The remaining H atoms were positioned geometrically and were refined as riding on their parent C atoms, with C-H distances of 0.93-0.97 Å; and with U iso (H) = 1.2U eq (C), except for the methyl groups where U iso (H) = 1.5U eq (C).

Dimethyl 2-[2-(2,4,6-trichlorophenyl)hydrazin-1-ylidene]butanedioate
Crystal data 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq