Selective Cobalt-Mediated Formation of Hydrogen Peroxide from Water under Mild Conditions via Ligand Redox Non-Innocence.

Despite the broad importance of hydrogen peroxide (HO) in oxidative transformations, there are comparatively few viable routes for its production. The majority of commercial HO is currently produced by the stepwise reduction of dioxygen (O) via the anthraquinone process, but direct electrochemical formation from water (HO) would have several advantages─namely, avoiding flammable gases or stepwise separations. However, the selective oxidation of HO to form HO over the thermodynamically favored product of O is a difficult synthetic challenge. Here, we present a molecular HO oxidation system with excellent selectivity for HO that functions both stoichiometrically and catalytically. We observe high efficiency for electrocatalytic HO production at low overpotential with no O observed under any conditions. Mechanistic studies with both calculations and kinetic analyses from isolated intermediates suggest that HO formation occurs in a bimolecular fashion via a dinuclear HO-bridged intermediate with an important role for a redox non-innocent ligand. This system showcases the ability of metal-ligand cooperativity and strategic design of the secondary coordination sphere to promote kinetically and thermodynamically challenging selectivity in oxidative catalysis.