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 oxid e (NO), nitrogen dioxide (NO2), nitrosyl fluoride (FNO), nitryl fluori de (FNO2), and nitrogen oxytrifluoride (F3NO) with the hexafluorides o f 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 r eacted 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]. Wi th NpF6, FNO reacted only under photolytic conditions to give (NO)[NpF 6], 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 actinid e hexafluorides, even under photolytic conditions. (C) 1998 Elsevier S cience S.A.