Nanoclusters of Iridium Oxide and of Rhodium Oxide Supported on MgO

MgO-supported Ir 4 and Rh 6, prepared from [Ir 4 (CO) 12 ] and [Rh 6 (CO) 16 ], respectively, on MgO, were partially oxidized at 323 K, with partial destruction of the metal frames, and reformed by treatment in H 2 . Oxidation at higher temperatures resulted in total oxidation of the clusters with breakup of the metal frames, and treatment in H 2 led to near reconstruction of the metal clusters, but with some migration and aggregation. The results imply that the oxidized nanoclusters were site isolated on the support surface; this is the first report of oxide clusters of noble metals. The metal oxide clusters are catalytically active for CO oxidation.