Metal complexes containing unpaired spin at a terminal oxo group have been invoked as key intermediates in numerous small molecule transformations for energy conversion and storage, including O–O bond formation in Co-OEC water oxidation catalysts. In contrast to closed-shell metal oxo compounds, isolated terminal metal oxyl radicals are exceedingly rare, challenging efforts to rationally incorporate metal oxyls in new catalysis cycles. We have found that oxorhenium complexes containing an appropriately positioned semiquinone ligand radical can exhibit oxyl-type O-atom transfer reactivity. Radical O–X coupling apparently occurs via facile interligand delocalization of the hole into the metal–oxo π-bonding manifold. This talk will present recent extensions of this “masked oxyl” strategy to very high-valent dioxorhenium complexes, formally one oxidation level above Re(VII), as well as redox-active ligand vanadyl and titanyl species relevant to single-site Ti(IV) photocatalysts.

Radical control at terminal metal oxos

254th National Meeting (2017)

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