5-(4-Pyridyl)-1,3,4-thiadiazole-2(3H)-thione

The title compound C7H5N3S2, occurs as the thione tautomer in the solid state; the dihedral angle between the pyridine and thiadiazole ring planes is 2.08 (6)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds, generating C(8) chains propagating in [010].

The title compound C 7 H 5 N 3 S 2 , occurs as the thione tautomer in the solid state; the dihedral angle between the pyridine and thiadiazole ring planes is 2.08 (6) . In the crystal, molecules are linked by N-HÁ Á ÁN hydrogen bonds, generating C(8) chains propagating in [010].

Comment
Thidiazoles had excellent biological activities, such as fungicide, KARI (Liu et al., 2007(Liu et al., , 2009a. Meanwhile, some nicotine structure are also exhibited good biological activity. In continuated our work, a thidiazoles derivatives had been synthesized. The strucuture was confirmed by X-ray crstallography. Single-crystal X-ray diffraction analysis reveals that the title compound crystallizes in the monoclinic space group P2(1)/ c. As shown in Fig. 1, the pyridine ring and the thiadiazole ring are nearly in the same plane [dihedral angle = 2.1 °]. As shown in Fig. 2, the crystal structure is stabilized by weak N-H···N intermolecular interactions.

Experimental
Potassium hydroxide (0.11 mol) was dissolved in minimum amount of ethanol, and 4-nicotinehydrazide (0.1 mol) was added to it. The reaction mixture was cooled to 0-5 °C followed by dropwise addition of carbon disulfide (0.11 mol). After addition, the reaction mixture was stirred for 30 min to afford solid potassium dithiocarbazate salt. It was filtered, washed with EtOH, dried, and used as such for further reaction. Potassium dithiocarbazate salt (0.1 mol) was added slowly in small lots to conc sulfuric acid (2.5 times of salt) at 5 °C with constant stirring. The reaction mixture was stirred for 30 min, and the resulting viscous liquid was poured over crushed ice slowly. The solid obtained was filtered and washed and dried to get the title compound. The compound was recrystallized in DMF to yield colorless prisms.

Refinement
All the H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and refined as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). Fig. 1. The molecular structure of (I). Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.

Figures
supplementary materials sup-2  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.