title: On the origins of faster oxo exchange for uranyl(V) versus plutonyl(V).
abstract: Activation of uranyl(V) oxo bonds in the gas phase is demonstrated by reaction of U(16)O(2)(+) with H(2)(18)O to produce U(16)O(18)O(+) and U(18)O(2)(+). In contrast, neptunyl(V) and plutonyl(V) are comparatively inert toward exchange. Computed potential energy profiles (PEPs) reveal a lower yl oxo exchange transition state for uranyl(V)/water as compared with neptunyl(V)/water and plutonyl(V)/water. A correspondence between oxo exchange rates in gas phase and acid solutions is apparent; the contrasting oxo exchange rates of UO(2)(+) and PuO(2)(+) are considered in the context of covalent bonding in actinyls. Hydroxo exchange of U(16)O(2)((16)OH)(+) with H(2)(18)O to give U(16)O(2)((18)OH)(+) proceeded much faster than oxo exchange, in accord with a lower computed transition state for OH exchange. The PEP for the addition of H(2)O to UO(2)(+) suggests that both UO(2)(+)·(H(2)O) and UO(OH)(2)(+) should be considered as potential products.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rios
authors.forename: Maria del Carmen
authors.initials: Mdel C
authors.lastname: Michelini
authors.forename: Ana F
authors.initials: AF
authors.lastname: Lucena
authors.forename: Joaquim
authors.initials: J
authors.lastname: Marçalo
authors.forename: John K
authors.initials: JK
authors.lastname: Gibson
mesh_terms: D010100:Oxygen / Q000737:chemistry*; D011005:Plutonium / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*
chemical_list: D014501:Uranium; D011005:Plutonium; D010100:Oxygen