Water oxidation at a tetraruthenate core stabilized by polyoxometalate ligands: Experimental and computational evidence to trace the competent intermediates

Converging UV-vis, EPR, rRaman, and DFT calculations highlight the evolution of [Ru₄(H₂O)₄(μ-O)₄(μ-OH)₂(γ-SiW₁₀O₃₆)₂]^10-, 1, to high-valent intermediates. In analogy with the natural enzyme, five different oxidation states, generated from 1, have been found to power the catalytic cycle for water oxidation. A high electrophilic tetraruthenium(V)-hydroxo species is envisaged as the competent intermediate, undergoing nucleophilic attack by an external water molecule as a key step in the formation of a new O-O bond under catalytic conditions.