Two 3-amino-1H-pyrazol-2-ium salts containing organic anions, and an orthorhombic polymorph of 3-amino-1H-pyrazol-2-ium nitrate

Co-crystallization from methanol of 3-amino-1H-pyrazole with 3,5-dinitro-benzoic acid produces 3-amino-1H-pyrazol-2-ium 3,5-dinitrobenzoate mono-hydrate, C₃H₆N₃+.C₇H₃N₂O₆-center dot H₂O, (I), while similar co-crystallization of this pyrazole with an equimolar quantity of fumaric acid produces bis(3-amino-1H-pyrazol- 2-ium) fumarate-fumaric acid (1/1), 2C(₃)H(₆)N(₃)(+)center dot C₄H₂O₄^2-center dot C₄H₄O₄, (II). The reaction of 3-amino-1H-pyrazole with a dilute solution of nitric acid in methanol yields a second, orthorhombic polymorph of 3-amino-1H-pyrazol-2-ium nitrate, C₃H₆N₃+center dot NO₃-, (III). In each of (I)-(III), the bond distances in the cation provide evidence for extensive delocalization of the positive charge. In each of (I) and (II), an extensive series of O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds links the components into complex sheets, while in the structure of (III), the ions are linked by multiple N-H center dot center dot center dot O hydrogen bonds into a threedimensional arrangement. Comparisons are made with the structures of some related compounds.