A hydrolytically stable Ce(iv) complex of glutarimide-dioxime

Abstract

The coordination chemistry of glutarimide-dioxime (H₃A) has been studied related to applications in uranyl sequestration from seawater and for the stabilization of early transition metals in high oxidation states. We report here that the H₂A⁻ anion is also suitable for stabilizing Ce(IV) and acts as a tridentate ligand to form the [Ce(H₂A)₃]⁺ cation. The metal complexes [Ce(H₂A)₃]Cl and [Ce(H₂A)₃][BPh₄] have been obtained by oxidation of Ce^III in the presence of H₃A under aerobic conditions. UV-Vis spectroscopy and DFT calculations were performed to characterize the electronic structure and ligand-to-metal charge transfer (LMCT) bands of [Ce^IV(H₂A)₃]⁺. X-ray absorption spectroscopy (XAS) was also performed to verify the Ce(IV) oxidation state. Absent a clear electrochemical signal for cerium reduction in [Ce(H₂A)₃]Cl or [Ce(H₂A)₃][BPh₄] under a range of conditions, DFT calculations predicted a Ce(III/IV) redox couple of −1.22 V vs. Fc/Fc⁺. These results further expand the coordination chemistry of glutarimide-dioxime to tetravalent cerium.