A fundamental challenge in uranium chemistry is the design of rational reactivity pathways for activation of the very strong and usually quite inert U–O bonds in the water-soluble uranyl(VI) dication [UO22+]. On the other hand, the uranyl(V) monocation [UO2+] can be formed by one-electron reduction, a reaction that has been shown to increase the Lewis basicity of the oxo groups and their tendency to engage in bonding with exogenous electrophilic reagents. Here, we report a new activation scheme for the uranyl ion that can be achieved either chemically or electrochemically using a moderately electrophilic borane reagent. The first step in our process is the clean formation of a metastable UV species on our ligand framework, as implicated by both NMR spectroscopy and spectroelectrochemical experiments. Electrokinetic monitoring of the functionalization process provides a tantalizing glimpse into the kinetics of the uranyl oxo functionalization chemistry, a multistep process that follows fast one-electron reduction and involves the formation of both mono- and bis-borylated species that are themselves redox active. Our most recent efforts will be discussed, including experiments aimed at the isolation of oxo-functionalized species.

Electrochemical activation of U–O bonds in the uranyl ion

ACS Spring 2022

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