Hexafluorophosphate

Hexafluorophosphate is an anion with chemical formula of PF−6. It is an octahedral species. It imparts no color to its salts. PF−6 is isoelectronic with sulfur hexafluoride, SF6, and the hexafluorosilicate dianion, SiF2−6, and fluoroantimonate SbF−6. Being poorly nucleophilic, hexafluorophosphate is classified as a non-coordinating anion.Hexafluorophosphate salts can be prepared by the reaction of phosphorus pentachloride and alkali or ammonium halide in a solution of hydrofluoric acid:Several methods of Quantitative analysis for the hexafluorophosphate ion have been developed. Tetraphenylarsonium chloride, Cl, has been used both for titrimetric and gravimetric quantifications of hexafluorophosphate. Both of these determinations depend on the formation of tetraphenylarsonium hexafluorophosphate:Hydrolysis is extremely slower under basic conditions. Acid-catalyzed hydrolysis to the phosphate ion is also slow. Nonetheless, hexafluorophosphate is prone to decomposition with the release of hydrogen fluoride in ionic liquids.Practical uses of the hexafluorophosphate ion typically exploit one or more of the following properties: that it is a non-coordinating anion; that hexafluorophosphate compounds are typically soluble in organic solvents, particularly polar ones, but have low solubility in aqueous solution; or, that it has a high degree of stability, including resistance to both acidic and basic hydrolysis.