Oxo ligand functionalization in the uranyl ion (UO22+)

Uranyl (UO₂²⁺) is an exceptionally stable molecular species, characterized by a linear OUO geometry and short U–O bonds. Its two oxo ligands are thought to be inert to exchange and resistant to functionalization. However, a growing body of literature suggests that this assessment may need to be reevaluated. This review summarizes the chemistry of the two oxo ligands of the uranyl ion. In particular, we explore the interaction of the uranyl oxo ligands with Lewis acids, and outline attempts to selectively functionalize the oxo ligands of uranyl by chemical means. We also discuss the kinetic and mechanistic knowledge for oxo ligand exchange under acidic, basic and photolytic conditions.