Electronic structure of molybdenum chalcogenide clusters as supports for low-valent actinides

The metallation, bonding, and electronic structure of redox active incomplete-cubane M₃(μ₃-Q)(μ₂-Q)₃ chalcogenide clusters with early actinides were studied using density functional theory and multireference methodologies. We confirmed that the incorporation of low-valent U(III) leads to its oxidation to U(IV) due to an intramolecular redox reaction with the molybdenum sulfide core. On the contrary, open questions remain with respect to the oxidation state of low-valent transuranic elements upon their coordination to the molybdenum sulfide core. Density functional theory calculations indicate that the transuranic center remains An(III), while complete active space calculations suggest an actinide oxidation analogous to the one observed in the uranium species. The predominantly electrostatic bonding between the actinides and the molybdenum sulfide cluster was assigned using the quantum theory of atoms in molecules. Our results on clusters with harder and softer chalcogenides are in agreement with a preferential soft-soft interaction between the actinide and its support.