Hydrolysis of Small Oxo/Hydroxo Molecules Containing High Oxidation State Actinides (Th, Pa, U, Np, Pu): A Computational Study

The energetics of hydrolysis reactions for high oxidation states oxo/hydroxo monomeric actinide species (ThIVO2, PaIVO2, UIVO2, PaVO2(OH), UVO2(OH), UVIO3, NpVIO3, NpVIIO3(OH), and PuVIIO3(OH)) were calculated at the CCSD(T) level. first step is formation a Lewis acid/base adduct with H2O (hydration), followed by proton transfer to form dihydroxide molecule (hydrolysis); this process repeated until all oxo groups are hydrolyzed. physisorption (hydration) each addition was predicted be exothermic, ca. −20 kcal/mol. products preferred energetically over hydration +IV +V states. compounds AnVI turning point in terms favoring hydrolysis. For AnVIIO3(OH), preferred, only two waters can bind; complete now endothermic, state An An(OH)7 +VI OH having one-half an electron. natural bond order charges reaction energies provide insights into nature hydrolysis/hydration processes. ionicity generally decrease across period. ionic character decreases as coordination number increase so that covalency increases moving right