A Reactive, Photogenerated High-Spin (<i>S</i>= 2) Fe<sup>IV</sup>(O) Complex via O<sub>2</sub>Activation
Jesse B. Gordon, Therese Albert, Aniruddha Dey, Sinan Sabuncu, Maxime A. Siegler, Eckhard Bill, Pierre Moënne‐Loccoz, David P. Goldberg
Abstract
Addition of dioxygen at low temperature to the non-heme ferrous complex FeII(Me3TACN)((OSiPh2)2O) (1) in 2-MeTHF produces a peroxo-bridged diferric complex Fe2III(μ-O2)(Me3TACN)2((OSiPh2)2O)2 (2), which was characterized by UV–vis, resonance Raman, and variable field Mössbauer spectroscopies. Illumination of a frozen solution of 2 in THF with white light leads to homolytic O–O bond cleavage and generation of a FeIV(O) complex 4 (ν(Fe=O) = 818 cm–1; δ = 0.22 mm s–1, ΔEQ = 0.23 mm s–1). Variable field Mössbauer spectroscopy measurements show that 4 is a rare example of a high-spin S = 2 FeIV(O) complex and the first synthetic example to be generated directly from O2. Complex 4 is highly reactive, as expected for a high-spin ferryl, and decays rapidly in fluid solution at cryogenic temperatures. This decay process in 2-MeTHF involves C–H cleavage of the solvent. However, the controlled photolysis of 2 in situ with visible light and excess phenol substrate leads to competitive phenol oxidation, via the proposed transient generation of 4 as the active oxidant.