Crystal structure of 2-azido-1H-imidazole-4,5-dicarbonitrile

In the title compound, C5HN7, the nitrile and azido substituents are close to being coplanar with the central ring. Molecules in the crystal are linked via an N—H⋯N hydrogen bond to a nitrile acceptor, forming a chain extending along the c-axis direction.


S1. Comment
Imidazoles have a storied history in the pharmaceutical (Windaus et al., 1907), ionic liquid (Katritzky et al., 2006), and energetic materials communities (Epishina et al. 1967). Recently, the title compound, C 5 HN 7 , appeared in a study of imidazoles as potential gas generators (Srinivas et al., 2014). Given this background, we synthesized the title compound to examine the crystal structure, reported herein.
Vigorous effervescence of liberated nitrogen gas occurred with each addition. The reaction was allowed to stir for a further 90 min after gas evolution ceased and was then extracted with ethyl acetate (4 x 20 ml). The organic layer was dried over magnesium sulfate and the solvent was removed by rotary evaporation to afford a light yellow solid. Crystals of the title compound suitable for X-ray diffraction were obtained by crystallization from ethyl acetate.

S3. Refinement
The hydrogen atom was located in a difference-Fourier and the positional parameters were fully refined, with U iso (H) set invariant at 0.08.

Figure 1
The molecular structure of the title compound with atom labeling. Ellipsoids are drawn at the 50% probability level, and the hydrogen atom is drawn as a sphere of arbitrary size.

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.