Novel Synthesis of ClF6+ and BrF6+ Salts†
For a compound in a given oxidation state, its oxidizing strength increases from its anion to the neutral parent molecule to its cation. Similarly, an anion is more easily oxidized than its neutral parent molecule, which in turn is more easily oxidized than its cation. This concept was systematically exploited in our search for new superoxidizers. Transition metal fluoride anions were prepared in their highest known oxidation states by high temperature/high pressure fluorinations with elemental fluorine and subsequently converted to their more strongly oxidizing cations by a displacement reaction with a strong Lewis acid. The application of this principle resulted in new syntheses for ClF6+AsF6- and BrF6+AsF6- using the highly reactive and thermally unstable NiF3+ cation that was prepared from the reaction of the NiF62- anion with AsF5 in anhydrous HF. Attempts to prepare the known KrF+ and ClO2F2+ cations and the yet unknown XeF7+ cation by the same method were unsuccessful. The results from this and pre...