Selective Formation of an FeIVO or an FeIIIOOH Intermediate From Iron(II) and H2O2: Controlled Heterolytic versus Homolytic Oxygen–Oxygen Bond Cleavage by the Second Coordination Sphere

• DOI: 10.1002/anie.201812724
• Publication Date: 2018-11-28T18:42:34Z
• Authors: Khaled Cheaib; M. Qadri E. Mubarak; Katell Sénéchal‐D...; Christian Herrero; Régis Guillot; Martin Clémancey; Jean‐Marc Latour; Sam P. de Visser; Jean‐Pierre Mahy; Frédéric Banse; Frédéric Avenier
• Keywords: iron complexes; O−O bond breaking; FeIV-oxo species; N ligands; [CHIM] Chemical Sciences; [CHIM]Chemical Sciences; 500; [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph]; 540; proton coupled electron transfer (PCET); [PHYS.PHYS.PHYS-CHEM-PH] Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph]

AbstractWe demonstrate that the devised incorporation of an alkylamine group into the second coordination sphere of an FeII complex allows to switch its reactivity with H2O2 from the usual formation of FeIII species towards the selective generation of an FeIV‐oxo intermediate. The FeIV‐oxo species was characterized by UV/Vis absorption and Mössbauer spectroscopy. Variable‐temperature kinetic analyses point towards a mechanism in which the heterolytic cleavage of the O−O bond is triggered by a proton transfer from the proximal to the distal oxygen atom in the FeII‐H2O2 complex with the assistance of the pendant amine. DFT studies reveal that this heterolytic cleavage is actually initiated by an homolytic O−O cleavage immediately followed by a proton‐coupled electron transfer (PCET) that leads to the formation of the FeIV‐oxo and release of water through a concerted mechanism.