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

Abstract

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.