Catalytic Methane Monofunctionalization by an Electrogenerated High-Valent Pd Intermediate

Electrophilic high-valent metal ions are potent intermediates for the catalytic functionalization of methane, but in many cases, their high redox potentials make these intermediates difficult or impossible to access using mild stoichiometric oxidants derived from O₂. Herein, we establish electrochemical oxidation as a versatile new strategy for accessing high-valent methane monofunctionalization catalysts. We provide evidence for the electrochemical oxidation of simple PdSO₄ in concentrated sulfuric acid electrolytes to generate a putative Pd₂^III,III species in an all-oxidic ligand field. This electrogenerated high-valent Pd complex rapidly activates methane with a low barrier of 25.9 (±2.6) kcal/mol, generating methanol precursors methyl bisulfate (CH₃OSO₃H) and methanesulfonic acid (CH₃SO₃H) via concurrent faradaic and nonfaradaic reaction pathways. This work enables new electrochemical approaches for promoting rapid methane monofunctionalization.