4-Ethyl-3-(2-thienylmethyl)-Δ2-1,2,4-triazoline-5-thione

The title compound, C9H11N3S2, exists in the thione form in the crystal structure. The central triazole ring is almost perpendicular to the thiophene ring which is disordered over two orientations [dihedral angles of 88.5 (7) and 85.7 (8)° for the two orientations]. The crystal structure is stabilized by strong intermolecular N—H⋯S hydrogen bonds, forming centrosymmetric dimers, and by some weak C—H⋯S interactions.

In the title compound ( Fig. 1), the C5-S1 bond length [1.673 (2) Å] is within the values observed for a C=S double bond.
In the planar 1,2,4-triazole ring the C3=N2 bond is clearly double, being much shorter then the other C-N bonds. This distance is also comparable to literature data (Yilmaz et al., 2005). The thiophene ring is disordered over two orientatians with respect to the C6-C7 bond; the dihedral angles between the triazole and the thiophene rings for the two orientations of the second one are 88.5 (7)  The crystal structure is stabilized by strong intermolecular N1-H1···S1 hydrogen bonds, forming centrosymmetric dimers ( Fig. 2), together with some weak C-H···S interactions (Table 1).

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with N1-H1 distance of 0.86Å and C-H bond distances in the range 0.93 -0.97 Å. The displacement parameters of the H atoms were U iso (H) = 1.2 U eq (C/N).
The thiophene ring is disordered over two positions related by a 180° rotation around the C6-C7 bond. This disorder gives rise to two positions for each of the S2 and C8 atoms; the refinement of their occupancies showed that one of these positions is predominant, with an occupancy of 0.538 (4) for S2 and C8 atoms [the other one is with an occupancy of 0.462 (6) Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. Both disordered components are shown.

4-Ethyl-3-(2-thienylmethyl)-Δ 2 -1,2,4-triazoline-5-thione
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 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.

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