Crystal structure of 2-amino-5-nitro­pyridinium sulfamate

The title mol-ecular salt, C5H6N3O2 (+) ·H2NO3S(-), was obtained from the reaction of sulfamic acid with 2-amino-5-nitro-pyridine. A proton transfer from sulfamic acid to the pyridine N atom occurred, resulting in the formation of a salt. As expected, this protonation leads to the widening of the C-N-C angle of the pyridine ring, to 122.9 (3)°, with the pyridinium ring being essentially planar (r.m.s. deviation = 0.025 Å). In the crystal, the ion pairs are joined by three N-H⋯O and one N-H⋯N hydrogen bonds in which the pyridinium N atom and the amino N atom act as donors, and are hydrogen bonded to the carboxyl-ate O atoms and the N atom of the sulfamate anion, thus generating an R (3) 3(22) ring motif. These motifs are linked by further N-H⋯O hydrogen bonds enclosing R (3) 3(8) loops, forming sheets parallel to (100). The sheets are linked via weak C-H⋯O hydrogen bonds, forming a three-dimensional structure. The O atoms of the nitro group are disordered over two sets of sites with a refined occupancy ratio of 0.737 (19):0.263 (19).