Highly selective synthesis of surface Fe IV =O with nanoscale zero-valent iron and chlorite for efficient oxygen transfer reactions

Abstract

High-valent iron-oxo species (Fe IV =O) has been a long-sought-after oxygen transfer reagent in biological and catalytic chemistry but suffers from a giant challenge in its gentle and selective synthesis. Herein, we propose a new strategy to synthesize surface Fe IV =O (≡Fe IV =O) on nanoscale zero-valent iron (nZVI) using chlorite (ClO 2 – ) as the oxidant, which possesses an impressive ≡Fe IV =O selectivity of 99%. ≡Fe IV =O can be energetically formed from the ferrous (Fe II ) sites on nZVI through heterolytic Cl–O bond dissociation of ClO 2 – via a synergistic effect between electron-donating surface ≡Fe II and proximal electron-withdrawing H 2 O, where H 2 O serves as a hydrogen-bond donor to the terminal O atom of the adsorbed ClO 2 – thereby prompting the polarization and cleavage of Cl-O bond for the oxidation of ≡Fe II toward the final formation of ≡Fe IV =O. With methyl phenyl sulfoxide (PMS 16 O) as the probe molecule, the isotopic labeling experiment manifests an exclusive 18 O transfer from Cl 18 O 2 – to PMS 16 O 18 O mediated by ≡Fe IV = 18 O. We then showcase the versatility of ≡Fe IV =O as the oxygen transfer reagent in activating the C-H bond of methane for methanol production and facilitating selective triphenylphosphine oxide synthesis with triphenylphosphine. We believe that this new ≡Fe IV =O synthesis strategy possesses great potential to drive oxygen transfer for efficient high-value-added chemical synthesis.