Bismuth Redox Catalysis
The ability of the main group element bismuth (Bi) to maneuver between different oxidation states in a catalytic redox cycle will be presented. We will show how Bi mimics the canonical organometallic steps of a transition metal, thus challenging the current dogmas of catalysis. A series of Bi complexes capable of two-electron redox catalysis have been unlocked and applied in various contexts of catalysis for organic synthesis. For example, capitalizing on the Bi(III)/Bi(V) redox pair, we have developed a catalytic protocol for the C‒F and C‒OTf  bond formation from aryl boronic esters. On the other hand, a low-valent redox manifold based on Bi(I)/Bi(III) enabled catalytic transfer hydrogenation, catalytic decomposition of inert nitrous oxide (N2O) and catalytic hydrodefluorination of C(sp2)‒F bonds. Recently, we have shown that one-electron pathways are also accessible, thus enabling a unique platform for synthesis based on SET processes through the triad Bi(I)/Bi(II)/Bi(III). Finally, we will also show how redox-neutral catalytic pathways can unlock novel organic transformations via canonical organometallic steps. For all methodologies, a combination of rational ligand design with an in depth analysis of all the catalytic steps proved crucial to unfold the catalytic properties of such a n intriguing element of the periodic table.