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

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.