4-[(E)-4-Bromobenzylideneamino]-3-[1-(4-isobutylphenyl)ethyl]-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C21H23BrN4S, the 4-bromobenzylidene group is disordered over two orientations with occupancies of 0.504 (5) and 0.496 (5). One of the methyl groups of the isobutyl unit is disordered over two sites with occupancies of 0.751 (19) and 0.249 (19). The benzene rings of the isobutylphenyl and bromophenyl (major disorder component) groups form dihedral angles of 71.63 (11) and 21.8 (3)°, respectively, with the triazole ring. In the crystal, centrosymmetrically related molecules exist as centrosymmetric N—H⋯S hydrogen-bonded dimers.

In the title compound, C 21 H 23 BrN 4 S, the 4-bromobenzylidene group is disordered over two orientations with occupancies of 0.504 (5) and 0.496 (5). One of the methyl groups of the isobutyl unit is disordered over two sites with occupancies of 0.751 (19) and 0.249 (19). The benzene rings of the isobutylphenyl and bromophenyl (major disorder component) groups form dihedral angles of 71.63 (11) and 21.8 (3) , respectively, with the triazole ring. In the crystal, centrosymmetrically related molecules exist as centrosymmetric N-HÁ Á ÁS hydrogen-bonded dimers.
Similarly Schiff base derivatives of 1,2,4-triazol-5-ones have been found to possess antitumor activity (Demirbas et al., 2004). In our earlier studies, we have reported the crystal structure of heterocyclic compounds containing both the ibuprofen and 1,2,4-triazole fragments (Fun et al., 2008a,b). Prompted by these observations and in continuation of our interest in the synthesis of chemically and biologically important heterocycles, we synthesized the title compound and report here its crystal structure.
The crystal packing (Fig 2) is consolidated by intermolecular N-H···S hygrogen bonds. These hydrogen bonds link centrosymmetrically related molecules into dimers.
Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.

Refinement
The (4-bromophenyl)methylidene group is disordered over two orientations with occupancies of 0.504 (5) and 0.496 (5), whereas, one of the methyl groups of the isobutyl unit is disordered over two sites with occupancies of 0.751 (19) and 0.249 (19). The corresponding bond distances in major and minor disorder components were restrained to be equal. The displacement parameters of atoms C19 and C19A were restrained to approximate isotropic behaviour. The N bound H atom was located in a difference map and was refined freely. C-bound H atoms were positioned geometrically [C-H = 0.93-0.98 Å] and refined using a riding model, with U iso (H) = 1.2U eq (C) and 1.5U eq (methyl C). A rotating-group model was used for the methyl groups. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Both disorder components are shown.   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 Rfactors(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.