Gas-phase nitrate complexes M(O)(NO3)n-1— are produced by elimination of NO2 from M(NO3)n—, where M is a lanthanide (Ln = Ce, Pr, Nd, Tb) or actinyl (AnO2 = UO2, NpO2, PuO2). The product has either a M-O. oxyl or M=O oxo bond, with respectively no change or an increase in M oxidation state. The reactivity of the oxyl/oxo towards hydrogen abstraction from donor gases to convert to M-OH reveals stabilities of LnIII vs. LnIV and AnVI vs. AnVII. Formation of Ln(O)(NO3)3— from LnIII(NO3)4— was expected to oxidize to LnIV for Ln = Ce and Pr based on Ln3+ ionization energies and Ln3+/4+ oxidation potentials. The actual result that PrIII is evidently more stable towards oxidation than TbIII is in apparent discord with ionization energies but in accord with oxidation potentials, which reflects that bond formation is not well represented by atomic or solution properties. Formation of AnO2(O)(NO)2— from AnVIO2(NO3)3— evidently results in oxidation to NpVII and intermediate PuVI/VII, which reveals decreasing stability of the heptavalent oxidation state beyond Np. The utility of this approach for probing known and new high oxidation states is being extended to other f-elements.

Exploring known and new high oxidation states in gas-phase complexes of F-elements

ACS Fall 2021

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