Radical Ligands Confer Nobility on Base-Metal Catalysts

The oxidation state of metals such as copper and iron can be stabilized by organic ligands that add or lose electrons and facilitate catalysis. The industrial preparation of many chemicals relies on the unparalleled rate and selectivity enhancements offered by metal compounds in solution. In many cases, the best catalysts rely on the scarcest elements, such as rhodium, iridium, and platinum. The cost of these materials has long driven efforts to make soluble catalysts out of cheaper, more Earth-abundant metals (1), often by modifying their reactivity with their surrounding ligands. This is especially true for catalyzing reduction-oxidation, or redox, reactions, which are critical not only in catalysis but in energy generation and storage. Such reactions usually change the oxidation state of the metal in solution. We discuss why there can be advantages to having the redox changes occur in the ligands instead.

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