Bimetallic Cluster Catalysts

Abstract

In homogeneous catalysis, bimetallic cluster compounds, possibly as catalytic active species, are expected to provide a synergistic effect for the catalytic activity because of the multi-centered metal atoms simultaneously involved in the catalytic reactions, e.g. CO+H2 into ethylene glycol or olefin hydroformylation. In some cases, metal clusters are easily decomposed into lower-nuclear subclusters as well as mononuclear species under the prevailing reaction conditions. On the other hand, bimetallic carbonyl clusters are used as a precursor to form a surface supported bimetallic ensembles having a high dispersion and well-defind metal compositions. Comparing with the conventionally prepared alloy catalysts, they exhibit a unique catalytic performance in effectively promoting the catalytic activity and in modifying the selectivity in some typical catalytic reactions such as CO+H2 reaction and olefin hydroformylation. The catalysis by supported bimetallic clusters is discussed in terms of their unique structural properties, morphologies, metal compositions and electronic interaction with metal oxides, carbon and polymers, which are studied by the different physical techniques such as EXAFS, Mossbauer, IR, NMR and XPS.