Reactions of hexafluorides of uranium, neptunium, and plutonium with nitrogen oxides and oxyfluorides.: Synthesis and characterization of (NO)[NpF6] and (NO)[PuF6]

A comparative study has been performed of the reactions of nitric oxide (NO), nitrogen dioxide (NO2), nitrosyl fluoride (FNO), nitryl fluoride (FNO2), and nitrogen oxytrifluoride (F3NO) with the hexafluorides of uranium, neptunium, and plutonium. Significant chemical differences among the hexafluorides were found. Thus, UF6 and excess NO reacted at room temperature to form the nitrosonium salt (NO)[UF6], the same U(V) product formed from the reaction of UF6 with excess NO2. Excess NO reacted rapidly with NpF6 to form poorly crystalline Np(IV) solids, but with an equimolar amount of PuF6 at reduced temperature NO reacted to yield a mixture of Pu(IV) species and the new compound (NO)[PuF6]. With NpF6, FNO reacted only under photolytic conditions to give (NO)[NpF6], whereas PuF6 oxidized FNO to give F3NO and a mixture of (NO)[PuF6] and Pu(IV) solids. No reaction was observed between NpF6 or PuF6 with FNO2. Likewise, no reaction was observed between F3NO and the actinide hexafluorides, even under photolytic conditions. (C) 1998 Elsevier Science S.A.