3-Nitro-1H-1,2,4-triazole

The asymmetric unit of the title compound, C2H2N4O2, contains two crystallographically independent molecules in which the triazole rings are essentially planar, with maximum deviations of 0.003 (1) Å in both molecules. The dihedral angle between the two 1H-1,2,4-triazole rings is 56.58 (5)°. In the crystal, molecules are linked via intermolecular N—H⋯N and C—H⋯O hydrogen bonds, forming a supramolecular chain along the b axis.

The asymmetric unit of the title compound, C 2 H 2 N 4 O 2 , contains two crystallographically independent molecules in which the triazole rings are essentially planar, with maximum deviations of 0.003 (1) Å in both molecules. The dihedral angle between the two 1H-1,2,4-triazole rings is 56.58 (5) . In the crystal, molecules are linked via intermolecular N-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds, forming a supramolecular chain along the b axis.

Experimental
Hot methanol solution (20 ml) of 3-nitro-1H-1,2,4-triazole (57 mg, Aldrich) was warmed over a heating magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature. Crystals of the title compound appeared from the mother liquor after a few days.

Refinement
Atoms H1N1 and H1N2 were located from a difference Fourier map and refined freely [refined N-H distances 0.857 (16) and 0.885 (15) Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(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.