Polymer‐protected bimetallic clusters with various alloying structures

Colloidal dispersions of polymer‐protected bimetallic cluster can be prepared by refluxing the alcoholic solutions of two kinds of metal ions in the presence of poly( N ‐vinyl‐2‐pyrrolidone). The bimetallic clusters thus prepared had higher activity as catalysts than the corresponding monometallic clusters. The structure of bimetallic clusters, analyzed by an Extended X‐ray Absorption Fine Structure(EXAFS) technique as well as ultraviolet‐visible(Uv‐vis) absorption spectra, depends on the preparation method. Some of them have a special core‐shell structure. The order of the tendency to be a core is estimated to be Au>Pt>Pd>Rh. This order could be explained by the redox potential of the corresponding metal ion and the coordination ability of the metal to polymer.