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Chemistry. 2017 Dec 6;23(68):17369-17378. doi: 10.1002/chem.201704193. Epub 2017 Nov 10.

Remarkably High Stability of Late Actinide Dioxide Cations: Extending Chemistry to Pentavalent Berkelium and Californium.

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Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA.
Department of Chemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama, 35487-0336, USA.
Department of Chemistry, Washington State University, Pullman, WA, 99164-4630, USA.


Actinyl chemistry is extended beyond Cm to BkO2+ and CfO2+ through transfer of an O atom from NO2 to BkO+ or CfO+ , establishing a surprisingly high lower limit of 73 kcal mol-1 for the dissociation energies, D[O-(BkO+ )] and D[O-(CfO+ )]. CCSD(T) computations are in accord with the observed reactions, and characterize the newly observed dioxide ions as linear pentavalent actinyls; these being the first Bk and Cf species with oxidation states above IV. Computations of actinide dioxide cations AnO2+ for An=Pa to Lr reveal an unexpected minimum for D[O-(CmO+ )]. For CmO2+ , and AnO2+ beyond EsO2+ , the most stable structure has side-on bonded η2 -(O2 ), as AnIII peroxides for An=Cm and Lr, and as AnII superoxides for An=Fm, Md, and No. It is predicted that the most stable structure of EsO2+ is linear [O=EsV =O]+ , einsteinyl, and that FmO2+ and MdO2+ , like CmO2+ , also have actinyl(V) structures as local energy minima. The results expand actinide oxidation state chemistry, the realm of the distinctive actinyl moiety, and the non-periodic character towards the end of the periodic table.


actinides; density functional calculations; gas-phase reactions; redox chemistry; transuranium elements


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