4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C8H8N4S, the planar triazole ring forms a dihedral angle of 13.7 (2)° with the phenyl ring. The crystal structure is stabilized by intermolecular N—H⋯S hydrogen-bond interactions, linking the molecules into chains along the a axis.

In the title compound, C 8 H 8 N 4 S, the planar triazole ring forms a dihedral angle of 13.7 (2) with the phenyl ring. The crystal structure is stabilized by intermolecular N-HÁ Á ÁS hydrogenbond interactions, linking the molecules into chains along the a axis.

Related literature
For the applications of triazole compounds, see: Xu et al. (2002); Jantova et al. (1998); Holla et al. (1996); Pevzner (1997). For bond-length data, see: Allen et al. (1987).  Table 1 Hydrogen-bond geometry (Å , ).  Comment 1,2,4-Triazole and its derivatives display a broad range of biological activities, finding application as antitumour, antibacterial, antifungal and antiviral agents (Xu et al., 2002;Jantova et al., 1998;Holla et al., 1996). Nitro derivatives of 1,2,4triazole are also of interest as highly energetic compounds (Pevzner, 1997). In addition, studies have been carried out on the electronic structures and the thiol-thione tautomeric equilibrium of heterocyclic thione derivatives. In the search for compounds with better biological activity, the title compound was synthesized and we report its crystal structure here.

Experimental
In the title compound ( Fig. 1), the C-S bond length of 1.675 (3) Å is in good agreement with the mean value of 1.660 Å reported by Allen et al. (1987). The triazole ring is strictly planar and makes a dihedral angle of 13.7 (2)° with the phenyl ring. The crystal packing ( Fig. 2) of is stabilized by intermolecular N-H···S hydrogen bonds (Table 1) linking the molecules into chains along the a axis.

Experimental
To a solution of KOH (0.015 mol, 0.840 g) and ethyl benzoate (0.01 mol, 1.50 g) in absolute ethanol (100 ml) was added CS 2 (0.015 mol, 0.91 ml). The mixture was diluted with absolute ethanol (50 ml) and shaken for 12 h. A suspension of the potassium salt, 98% hydrazine hydrate (0.03 mol, 15 ml) and absolute ethanol (10 ml) was refluxed with stirring for 4 h.
Dilution with cold water (100 ml) and acidification with concentrated HCl precipitated a white solid. The product was then filtered and washed with cold water. Colourless crystals of the title compound suitable for X-ray diffraction analysis were obtained by slow evaporation of a solution of 100 mg in 15 ml diethylether after 3 days.

Refinement
All H atoms were initially located in a difference Fourier map, then they were constrained to ride on their parant atoms with C-H = 0.93 Å, N-H = 0.86-0.89 Å and with U iso (H) = 1.2 U eq (C, N). Fig. 1. The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.  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.