Carbon-carbon bond forming reactions catalyzed by heterogeneous Pd and Rh nanoparticles

Abstract

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.