Synergistic catalysis of PtRu oxide cluster for arene C–H bond activation

Oxidative coupling reactions of arenes and carboxylic acids are highly efficient molecular transformation affording aryl esters from nonactivated substrates. The conventional catalytic reactions were usually carried out with oxidants such as hypervalent iodine reagents, silver salts, organic peroxides, and persulfates. From the viewpoints of atom economy, availability, and nontoxicity, molecular oxygen (O₂) is a more favorable oxidant. Catalysts for the oxidative coupling using O₂ as an oxidant were also reported but much less studied. In this study, we developed the PtRu oxide clusters supported on activated carbon (PtRuO_x/C) by simple preparation method. The formation of PtRuO_x with mean diameter of 1.1 nm was clarified by using AC-HAADF-STEM, EDS, XAS, and XPS. It was found that the catalytic activity of PtRuO_x/C for the acetoxylation of benzene using O₂ oxidant was enhanced by the synergistic effect between Pt and Ru. Kinetic measurements and DFT calculations indicated that the arene C–H bond activation proceeded by electrophilic concerted metalation deprotonation mechanism and that the surface Pt atom of PtRuO_x mainly acted as the active site for the C–H bond activation.