Hexafluorophosphoric acid

Hexafluorophosphoric acid is the inorganic compound with the chemical formula H2FPF6 (also written H2F). This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (PF−6). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride. Hexafluorophosphoric acid is the inorganic compound with the chemical formula H2FPF6 (also written H2F). This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (PF−6). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride. Like many strong acids, hexafluorophosphoric acid is not isolable but is handled only in solution. It exothermically reacts with water to produce oxonium hexafluorophosphate (H3OPF6) and hydrofluoric acid, both of which are strong acids. Additionally, such solutions often contain products derived from hydrolysis of the P-F bonds, including HPO2F2, H2PO2F, and H3PO4, and their conjugate bases. Hexafluorophosphoric acid attacks glass. Upon heating, it decomposes to generate HF. Crystalline HPF6 has been obtained as the hexahydrate, wherein PF−6 is enclosed in truncated octahedral cages defined by the water and protons. NMR spectroscopy indicates that solutions derived from this hexahydrate contain significant amounts of HF.