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

The coordination chemistry of glutarimide-dioxime (H(3)A) 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 H(2)A(-) anion is also suitable for stabilizing Ce(iv) and acts as a tridentate ligand to form the [Ce(H(2)A)(3)](+) cation. The metal complexes [Ce(H(2)A)(3)]Cl and [Ce(H(2)A)(3)][BPh4] have been obtained by oxidation of Ce-III in the presence of H(3)A 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(H(2)A)(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(H(2)A)(3)]Cl or [Ce(H(2)A)(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.

Automated summary

In this study, it was found that the anion H(2)A(-) can stabilize Ce(IV) and form a tridentate complex with cerium, oxidizing Ce-III to Ce-IV under aerobic conditions. UV-Vis spectroscopy, DFT calculations, and X-ray absorption spectroscopy were used to characterize the electronic structure and oxidation state of the cerium complexes. Despite the lack of clear electrochemical signal for cerium reduction, DFT calculations predicted a Ce(iii/iv) redox couple of -1.22 V vs. Fc/Fc(+). These results expand the understanding of the coordination chemistry of glutarimide-dioxime to include tetravalent cerium.