Heterogeneous catalysts have attracted recent attention in various research areas because of advantageous properties such as facile reactivity tuning, recyclability, easy separation from the reaction mixture, and compatibility for large-scale industrial processes.
However, heterogeneous nanoparticles (NPs) catalysts have been limited to serve low-valent metal surfaces, although homogeneous catalytic reactions covered a wide range of catalysis including low-valent and high-valent metal catalysis.
Here we introduce the surface oxidation of Pd and Rh NPs to provide high-valent metal spe-cies for catalytic C-C bond formation. By simple treatment with oxidants, high-valent metal species can be efficiently generated from the original metal(0). Heterogeneous nanoparticles were successfully characterized by XPS, XAFS, and TEM.
First, we focused on generating high-valent Pd (II) using oxidant and applying to C-H aryla-tion reactions. Second, Rh(I) species with cod ligand have been applied to the 1,4-addition of phenylboronic acids to cyclohexenone.
Both Pd and Rh NPs show high reactivity as well as outstanding stability for recycling with-out leaching of the metals.