Nanoclusters of iridium oxide and of rhodium oxide supported on MgO

MgO-supported Ir-4 and Rh-6, prepared from [lr(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.