Mechanistic Aspects of Cobalt-Oxo Cubane Clusters in Oxidation Chemistry

Cobalt oxides are recognized as one of the most efficient earth-abundant catalysts for challenging oxidation chemistry, with substrates ranging from water to organic compounds. In these oxidations, cobalt-oxo species with formal oxidation states greater than 3 are commonly invoked as reactive intermediates. However, there is a dearth of mechanistic information regarding how these high-valent cobalt catalysts operate. This Perspective describes how the study of molecular cobalt oxo clusters, with an emphasis on [Co4O4] oxo cubane complexes, has helped to shed light on the operative mechanisms of cobalt-catalyzed oxidation reactions. Implications for high-valent Co-IV-oxo and Co-V-oxo intermediates and remaining mechanistic questions concerning how these intermediates mediate O-O bond formation are also discussed. Furthermore, structural modifications of these oxo cubane clusters (i.e., incorporation of heteroatoms and modulation of ligands) have provided insight into multimetallic cooperativity, but the influence of such metal-metal interactions on oxidation activity remains to be explored. A more detailed understanding of these structure-activity relationships may enable fine-tuning of reactivity and stability of synthetic multimetallic catalysts for energy storage and challenging organic transformations.

Automated summary

Cobalt oxides are efficient catalysts for oxidation reactions, but the mechanisms of these reactions are not well understood. The study of cobalt oxo clusters, especially [Co4O4] oxo cubane complexes, has provided insights into the operative mechanisms of cobalt-catalyzed oxidation reactions and the formation of high-valent cobalt intermediates and O-O bonds. Structural modifications of these clusters have also shed light on multimetallic cooperativity. A better understanding of these structure-activity relationships may allow for the fine-tuning of synthetic catalysts for energy storage and organic transformations.