The gas-phase complexes AnO2(CH3CO2)2– are actinyl(V) cores, AnVO2+ (An = U, Np, Pu), coordinated by acetate ligands. Whereas the addition of O2 to UVO2(CH3CO2)2– exothermically produces the superoxide complex UVIO2(O2)(CH3CO2)2–,1 this oxidation does not occur for NpVO2(CH3CO2)2– or PuVO2(CH3CO2)2– because of the higher Np(V) and Pu(V) reduction potentials. However, NO2 is a more effective electron-withdrawing oxidant than O2, with the result that all three AnVO2(CH3CO2)2– exothermically add NO2 to form nitrite complexes, reaction (1).2 AnVO2(CH3CO2)2- + NO2 --&gt; AnVIO2(CH3CO2)2(NO2) – (1) The assignment of the NO2– anion ligand, resulting in oxidation from An(V) to An(VI), is substantiated by the replacement of the acetate ligands in AnO2(CH3CO2)3– by nitrites, to produce AnO2(NO2)3–. This observation, which appears to contradict the higher electron affinity of acetate vs. nitrite, is attributed to the metathesis reaction (2), where the HNO2 reactant is produced by hydrolysis of NO2. AnO2(CH3CO2)3– + 3HNO2 --&gt; AnO2(NO2)3– + 3CH3COOH (2) The oxidation of An(V) to An(VI) by the addition of neutral NO2 is established by the substitution of acetate by nitrite. We have thus demonstrated that actinyl(VI/V) reduction potentials are sufficiently low, and different from one another, that two neutral molecules, O2 and NO2, with electron affinities that differ by ca. 2 eV, can selectively oxidize U(V), Np(V) and Pu(V). The work of PDD, WWL and JKG was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Heavy Element Chemistry, at LBNL under Contract No. DE-AC02-05CH11231. JMC and JM were supported by Fundação para a Ciência e a Tecnologia/Portugal through Project UID/Multi/04349/2013. 1. A. F. Lucena, J. M. Carretas, J. Marçalo, M. C. Michelini, Y. Gong, J. K. Gibson, J. Phys. Chem. A 119 (2015) 3628-3635 2. P. D. Dau, J. M. Carretas, J. Marçalo, W. W. Lukens, J. K. Gibson, Inorg. Chem. 54 (2015) 8755-8760.

Oxidation of actinyl(V) by addition of nitrogen dioxide revealed via replacement of acetate by nitrite

251st National Meeting (2016)

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