Reversible Single-Electron-Transfer to Oxygen in a Stable N-Heterocyclic Carbene Palladium(I) Metalloradical.

The chemical and electrochemical one-electron oxidation of [Pd(IPr)] () leads to the formation of mononuclear palladium(I) complex [Pd(IPr)][PF] (). This bench-stable metalloradical has been fully characterized and its structure confirmed by X-ray diffraction analysis. EPR and DFT studies confirm the localization of the unpaired electron onto the metal center. Low temperature NMR and EPR measurements reveal the ability of complex to reversibly coordinate and reduce the dioxygen molecule, leading to the formation of a three-coordinate complex, [Pd(IPr)(η-O)] (), in which the unpaired electron has been transferred to the superoxido ligand.