Cooperation of cerium oxide nanoparticles and soluble molecular catalysts for alcohol oxidation

Abstract

Cerium oxide (ceria, CeO_2−x) has been traditionally used as a catalyst support functionalized with metal nanoparticles or synthesized with metal dopants for a variety of applications ranging from catalytic converters to solid oxide fuel cells. In a departure from these typical heterogeneous motifs, we explore the interactions of nano-CeO_2−x systems with organometallic oxidation catalysts in organic solvents. Ceria is used here both as an organically-capped colloid and as an uncapped insoluble nanopowder. Both the colloid and nanopowder act as terminal oxidants by accepting hydrogen atoms from a ruthenium Noyori–Ikariya hydride complex. To our knowledge, this is the first demonstration that CeO_2−x can oxidize an organometallic hydride. Building on this concept, we show the uncapped CeO_2−x powder also acts as the terminal acceptor in catalytic alcohol dehydrogenation reactions, utilizing iridium pyridine sulfonamide catalysts under anaerobic and aerobic conditions. The coupling of homogeneous oxidation catalysts with cerium oxide demonstrates the versatility of CeO_2−x and a bridging of concepts in homogeneous and heterogeneous catalysis.