Understanding the Differential Performance of Rh2(esp)2 as a Catalyst for C−H Amination

Catalytic amination of saturated C−H bonds is performed efficiently with the use of Rh2(esp)2. Efforts to identify pathways for catalyst degradation and/or arrest have revealed a single-electron oxidation event that gives rise to a red-colored, mixed-valence dimer, [Rh2(esp)2]+. This species is fortuitously reduced by carboxylic acid, a byproduct generated in the reaction cycle with each turnover of the diacyloxyiodine oxidant. These findings have led to the conclusion that the high performance of Rh2(esp)2 is due in part to the superior kinetic stability of its one-electron oxidized form relative to other dimeric Rh complexes.