The potential energy surfaces corresponding to the dehydrogenation reaction of H2O, NH3, and CH4 molecules by Fe+(6D, 4F) cation have been investigated in the framework of the density functional theory in its B3LYP formulation and employing a new optimized basis set for iron. In all cases, the low-spin ion−dipole complex, which is the most stable species on the respective potential energy hypersurfaces, is initially formed. In the second step, a hydrogen shift process leads to the formation of the insertion products, which are more stable in a low-spin state. From these intermediates, three dissociation channels have been considered. All of the results have been compared with existing experimental and theoretical data. Results show that the three insertion pathways are significantly different, although spin crossings between high- and low-spin surfaces are observed in all cases. The topological analysis of the electron localization function has been used to characterize the nature of the bonds for all of the minima and transition states along the paths.

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.

The ability of uranium monoxide cations, UO+ and UO2+, to activate the O-H bond of H2O was studied by using two different approaches of the density functional theory. First, relativistic small-core pseudopotentials were used together with B3LYP hybrid functional. In addition, frozen-core PW91-PW91 calculations were performed within the ZORA approximation. A close description of the reaction mechanisms leading to two different reaction products is presented, including all the involved minima and transition states. Different possible spin states were considered as well as the effect of spin-orbit interactions on the transition state barrier heights. The nature of the chemical bonding of the key minima and transition states was studied by using topological methodologies (ELF, AIM). The obtained results are compared with experimental data, as well as with previous studies on the reaction of the bare uranium cations with water, to analyze the influence of the oxo-ligand in reactivity.

Th + is the only actinide ion that activates exothermically the strong C-H bonds of methane in the gas phase. In contrast, U + , as well as all of the rest of the experimentally studied An + cations, is inert in the reaction with CH 4 . In this work, the activation of methane by thorium and uranium monocations was investigated using two different density functional theory approaches. The reaction mechanisms and the corresponding potential energy profiles were analyzed in detail. From the formation of the initial ion-molecule adduct, the Th + +CH 4 reaction pathway evolves completely along the doublet spin surface, whereas that of U + +CH 4 involves solely the quartet bare cation ground spin state. The bonding properties of all of the species involved in the reaction pathways were investigated in terms of diverse analyses including natural bond orbital, atoms in molecules, and electron localization function. The dehydrogenation products (Th + dCH 2 and U + dCH 2 ) as well as the last insertion intermediates are characterized by the presence of R-agostic geometries.

Density functional theory calculations were performed to study the gas-phase reaction of Th(+) and Th(2+) with water. An in-depth analysis of the reaction pathways leading to different reaction products is presented. The obtained results are compared to experimental data and to the previously studied reactions of U cations with water.