5-(2-Fluoro-4-nitrophenyl)-1,3,4-thiadiazole-2-amine

The title compound, C8H5FN4O2S, was synthesized by the reaction of 2-fluoro-4-nitrobenzoic acid and thiosemicarbazide. The dihedral angle between the thiadiazole and benzene rings is 27.1 (2)°. In the crystal, intermolecular N—H⋯N and C—H⋯O hydrogen bonds link the molecules.

The title compound, C 8 H 5 FN 4 O 2 S, was synthesized by the reaction of 2-fluoro-4-nitrobenzoic acid and thiosemicarbazide. The dihedral angle between the thiadiazole and benzene rings is 27.1 (2) . In the crystal, intermolecular N-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds link the molecules.
The structure of the title compound, (I), is shown in Fig. 1, in which the bond lengths and angles are generally within normal ranges (Allen et al., 1987). The dihedral angle between the thiadiazole and benzene ring is 27.1 (2)°. There are intermolecular N-H···N and C-H···O hydrogen bonds, linking the molecules, forming chains along the b axis ( Fig. 2),.

S2. Experimental
2-Fluoro-4-nitrobenzoic acid (2 mmol) and thiosemicarbazide (5 mmol) were mixed in a 25 ml flask, and kept in the oil bath at 363 K for 6 h. After cooling, the crude product (I) precipitated and was filted. Pure compound (I) was obtained by crystallization from ethanol (20 ml). Crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of an acetone solution.

S3. Refinement
H atoms were placed geometrically with C-H = 0.93 Å and N-H = 0.86 Å, and included in the refinement in riding motion approximation with U iso (H) = 1.2 or 1.5U eq of the carrier atom.

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