Crystal structure of (1,4-diphenyl-4H-1,2,4-triazol-3-yl)phenyl-amine di-fluoro-phosphate, and a survey of the di-fluoro-phosphate anion (PO(2)F(2) (-)).

Nitron is the trivial name of (1,4-diphenyl-4H-1,2,4-triazol-3-yl)phenyl-amine (C(20)H(16)N(4)), a triazole derivative used as an analytical reagent for gravimetric analysis of the nitrate anion. The crystal structure of the di-fluoro-phosphate salt of Nitron, 3-anilino-1,4-diphenyl-1H-1,2,4-triazol-4-ium di-fluoro-phosphate, C(20)H(17)N(4) (+)·PO(2)F(2) (-), is reported here. Within the protonated Nitron mol-ecule, 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)°. Inter-molecular N-H⋯O and C-H⋯O hydrogen bonds between cations and di-fluoro-phosphate anions lead to the formation of a three-dimensional network that is consolidated by additional π-π stacking inter-actions between the triazole ring and one of the phenyl rings. Database surveys on inorganic, metal-organic and organic structures comprising the tetra-hedral PO(2)F(2) group reveal mean bond lengths of P-O = 1.459†(27)†à , P-F = 1.530†(21)†à , 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 PO(2)F(2) (-) anions or PO(2)F(2) entities.