3-Benzyl-4-ethyl-1H-1,2,4-triazole-5(4H)-thione

The title compound, C11H13N3S, exists in the 5-thioxo tautomeric form. The benzene ring exhibits disorder with a refined ratio of 0.77 (2):0.23 (2) for components A and B with a common bridgehead C atom. The 1,2,4-triazole ring is essentially planar, with a maximum deviation of 0.002 (3) Å for the benzyl-substituted C atom, and forms dihedral angles of 88.94 (18) and 86.56 (49)° with the benzene rings of components A and B, respectively. The angle between the plane of the ethyl chain and the mean plane of 1,2,4-triazole ring is 88.55 (15)° and this conformation is stabilized by an intramolecular C—H⋯S contact. In the crystal, pairs of N—H⋯S hydrogen bonds link molecules into inversion dimers. π–π interactions are observed between the triazole and benzene rings, with centroid–centroid separations of 3.547 (4) and 3.544 (12) Å for components A and B, and slippages of 0.49 (6) and 0.58 (15) Å, respectively.

The title compound, C 11 H 13 N 3 S, exists in the 5-thioxo tautomeric form. The benzene ring exhibits disorder with a refined ratio of 0.77 (2):0.23 (2) for components A and B with a common bridgehead C atom. The 1,2,4-triazole ring is essentially planar, with a maximum deviation of 0.002 (3) Å for the benzyl-substituted C atom, and forms dihedral angles of 88.94 (18) and 86.56 (49) with the benzene rings of components A and B, respectively. The angle between the plane of the ethyl chain and the mean plane of 1,2,4-triazole ring is 88. 55 (15) and this conformation is stabilized by an intramolecular C-HÁ Á ÁS contact. In the crystal, pairs of N-HÁ Á ÁS hydrogen bonds link molecules into inversion dimers.

Experimental
The title compound, (I), was prepared by the cyclization reaction of 1-benzyl-4-ethylthiosemicarbazide in alkaline medium according to the metod described by Dobosz & Pachuta-Stec (1996). Crystals uitable for X-ray diffraction analysis were grown by slow evaporation of ethanol solution.

Refinement
The benzene ring exhibits disorder with the refined ratio of 0.77 (2) The remaining H atoms were positioned geometrically and treated as riding on their C atoms with C-H distances of 0.93 Å (aromatic), 0.96 Å (CH 2 ) and 0.97 Å (CH 3 ). All H atoms were assigned U iso (H) values of 1.5U eq (N,C).

Figure 1
The molecular structure of (I), with atom labels and 30% probability displacement ellipsoids for non-H atoms.

Figure 2
A view of the molecular packing in (I).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 Occ. (