Bis-Nitrene Prevails: Ligand-Controlled Divergence from the Conventional Mononitrene Pathway in Dirhodium Catalysis

Abstract Dirhodium paddlewheel complexes are widely used in C–H amination, yet whether bis-nitrene intermediates participate in catalysis remains an open question. Through systematic DFT calculations at the M06L/dgdzvp/SMD level, we show that both axial and bridging ligands exert strong control over the relative stability of mono-versus bis-nitrene species. Key to this control is π-backdonation from the Rh–Rh π orbital into the vacant p orbital of the nitrene, which stabilizes triplet intermediates and facilitates bis-nitrene formation. The electronic structures of mono- and bis-nitrenes differ in a fundamental way: spin density is distributed across the Rh–Rh–N framework in mononitrenes, whereas it becomes localized on individual Rh–N bonds in bis-nitrenes. These findings establish ligand-controlled spin-state modulation as a key determinant of intermediate speciation, providing new physical insights into dirhodium-catalyzed C–H amination.