Formula HPF6 Appearance colorless oily liquid | Molar mass 145.972 g/mol | |
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Hexafluorophosphoric acid is the inorganic compound with the chemical formula H3OPF6. Although the formula is often written as HPF6, this compound is only available as the hydrate. 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. Its aqueous solutions consist of hydronium ion, H
3O+
, and PF−
6. Additionally, such solutions often contain products derived from hydrolysis of the P-F bonds, including HPO
2F
2, H
2PO
2F, and H
3PO
4, and their conjugate bases. Hexafluorophosphoric acid attacks glass. Upon heating, it decomposes to generate HF. Crystalline HPF
6 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.