Iridium Nitrido to Nitrosyl Oxygenation via Proton-Coupled Electron Transfer: Isolation of an {Ir(NO)}9 Intermediate

The oxygenation of transition-metal nitrido complexes to nitrosyl complexes is a key reaction for strategies that aim at generating nitrogenous oxides (NOx) from low-valent nitrogen compounds (N2 or NH3). Oxygen atom transfer from reagents such as amine-N-oxides or N2O to electrophilic nitrides has been previously reported. In contrast, oxidation in the presence of water as an oxygen source has not been broadly examined. We here report a high-yield protocol for the oxygenation of a square-planar iridium(V) nitrido complex to the respective {Ir(NO)}8 nitrosyl product, using hydroxide as oxygen source. Furthermore, an {Ir(NO)}9 intermediate was isolated. Its crystallographic, spectroscopic, and computational characterization confirmed strongly bent nitrosyl coordination due to predominantly NO-centered radical localization.