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

Abstract

Co-crystallization from methanol of 3-amino-1H-pyrazole with 3,5-dinitrobenzoic acid produces 3-amino-1H-pyrazol-2-ium 3,5-dinitrobenzoate monohydrate, C3H6N3 +·C7H3N2O6 −·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), 2C3H6N3 +·C4H2O4 2−·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 +·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...O and N—H...O hydrogen bonds links the components into complex sheets, while in the structure of (III), the ions are linked by multiple N—H...O hydrogen bonds into a three-dimensional arrangement. Comparisons are made with the structures of some related compounds.