Nonheme oxoiron(iv) complexes of pentadentate N5 ligands: spectroscopy, electrochemistry, and oxidative reactivity

摘要: Oxoiron(IV) species have been found to act as the oxidants in catalytic cycles of several mononuclear nonheme iron enzymes that activate dioxygen. To gain insight into factors govern oxidative reactivity such complexes, a series five synthetic S = 1 [FeIV(O)(LN5)]2+ complexes has characterized with respect their spectroscopic and electrochemical properties well relative abilities carry out oxo transfer hydrogen atom abstraction. The FeO units these are supported by neutral pentadentate ligands having combination pyridine tertiary amine donors but different ligand frameworks. Characterization X-ray absorption spectroscopy reveals bonds ca. 1.65 A length give rise intense 1s → 3d pre-edge features indicative centers substantial deviation from centrosymmetry. Resonance Raman studies show exhibit ν(FeO) modes at 825–841 cm−1. Spectropotentiometric experiments acetonitrile 0.1 M water reveal supporting modulate E1/2(IV/III) redox potentials values ranging 0.83 1.23 V vs. Fc, providing first determination for oxoiron(IV) complexes. 0.4 difference potential may arise differences number on LN5 orientations bond enforced architecture. rates oxo-atom (OAT) thioanisole correlate linearly increase potentials, reflecting electrophilicities units. However this linear relationship does not extend hydrogen-atom (HAT) 1,3-cyclohexadiene (CHD), 9,10-dihydroanthracene (DHA), benzyl alcohol, suggesting HAT reactions governed thermodynamics alone. This study represents investigation compare FeIVO frameworks sheds some light complexities unit.