Iron-Substituted Polyoxotungstates as Inorganic Synzymes: Evidence for a Biomimetic Pathway in the Catalytic Oxygenation of Catechols

Combined and convergent structural, spectroscopic, and mechanistic evidence on the bio-inspired catalysis by Krebs-type Fe4X2W 18 polytungstates in promoting the cleavage of catechols was reported. The biomimetic function of the polyoxometalates (POM)-based catalyst was assessed by spectroscopic and structure-reactivity relationships. The results show that the cleavage products are generated from the rearrangement and hydrolysis of a transient alkylperoxo intermediate. The biometric Fe-catecholate intermediates show two catecholate-to-Fe charge transfer bands in UV/Vis-NIR spectra. The energies of the catecholate-to-Fe charge-transfer transitions can be tuned by the POM composition and these bands provide a sensitive probe for the Lewis acidity of the iron center.