Supported Pd Nanoparticles with a Metallic and Oxidized Multisite for Sustainable Suzuki–Miyaura-Type C–H Arylation

Here, we demonstrated that γ-Al2O3-supported palladium nanoparticles containing dominant metallic-state Pd sites and charged Pd (Pd2+ and Pd1+) sites are a highly active, selective, and stable heterogeneous catalyst for a variety of Suzuki-Miyaura-type C(sp3)-H or C(sp2)-H arylation reactions, resulting in a high cumulative turnover number (TON) of 226 after 6 runs. Multi-technique characterization data, including X-ray absorption fine structure (XAFS) analyses, showed that both the strong metal-support interaction (SMSI) with Pd-O coordination and the fitting increase of metal-metal bonds after reaction efficiently limit Pd leaching and Pd0 aggregates. The support concerted metalation-deprotonation (SCMD) effect of Pd/γ-Al2O3 is more favorable for the proceeding of the Pd2+/Pd0 catalytic cycle at the microenvironment. This study sheds light on a new approach for heterogenization of homogeneous palladium catalysts in inert C-H bond activation reactions.