Optimization of Metal–Support\nCooperation for\nBoosting the Performance of Supported Gold Catalysts for the Borylation\nof C–O and C–N Bonds

The cooperation of multiple catalytic components is a\npowerful\ntool for intermolecular bond formation, specifically, cross-coupling\nreactions. Supported metal catalysts have interfacial sites between\nmetal nanoparticles and their supports where multiple catalytic elements\ncan work in cooperation to efficiently promote intermolecular reactions.\nHence, the establishment of novel guidelines for designing active\ninterfacial sites of supported metal catalysts is indispensable for\nheterogeneous catalysts which enable efficient cross-coupling reactions.\nIn this article, we performed kinetic and theoretical studies to elucidate\nthe effect of metal–support cooperation for the borylation\nof C–O bonds by supported gold catalysts and revealed that\nthe Lewis acid density of the supports determined the number of active\nsites at which metal nanoparticles (NPs) and Lewis acid at the surface\nof the supports work in cooperation. Furthermore, DFT calculations\nrevealed that strong adsorption of diborons at the interface between\nAu NPs and supports and a decrease in the LUMO level of adsorbed diboron\nwere responsible for efficient C–O bond borylation. Supported\nAu catalysts with the optimized metal–metal oxide cooperation\nsites, namely, Au/α-Fe<sub>2</sub>O<sub>3</sub> catalyst, showed\nexcellent activity for C–O bond borylation, and also enabled\nthe synthesis of organoboron compounds by using continuous-flow reactions.\nFurthermore, Au/α-Fe<sub>2</sub>O<sub>3</sub> showed high activity\nfor direct C–N bond borylation without the transformation of\namino groups to ammonium cations. The results described herein suggest\nthat the optimization of metal–metal oxide cooperation is beneficial\nfor taking full advantage of the potential performance of supported\nmetal catalysts for intermolecular reactions.