Crystal structure of (1,4-diphenyl-4H-1,2,4-triazol-3-yl)phenylamine difluorophosphate, and a survey of the difluorophosphate anion (PO2F2 −)

Abstract

Nitron is the trivial name of (1,4-diphenyl-4H-1,2,4-triazol-3-yl)phenylamine (C20H16N4), a triazole derivative used as an analytical reagent for gravimetric analysis of the nitrate anion. The crystal structure of the difluorophosphate salt of Nitron, 3-anilino-1,4-diphenyl-1H-1,2,4-triazol-4-ium difluorophosphate, C20H17N4 +·PO2F2 −, is reported here. Within the protonated Nitron molecule, the triazole ring, one of the phenyl rings and the NHPh moiety are virtually co-planar, with the third phenyl ring inclined to the least-squares plane of the other three rings by 56.07 (3)°. Intermolecular N—H...O and C—H...O hydrogen bonds between cations and difluorophosphate anions lead to the formation of a three-dimensional network that is consolidated by additional π–π stacking interactions between the triazole ring and one of the phenyl rings. Database surveys on inorganic, metal–organic and organic structures comprising the tetrahedral PO2F2 group reveal mean bond lengths of P—O = 1.459 (27) Å, P—F = 1.530 (21) Å, and angles of O—P—O = 121.2 (2.9)°, O—P—F = 108.7 (6)°, and F—P—F = 98.5 (2.6)°, using a dataset of 67 independent PO2F2 − anions or PO2F2 entities.