SURFACE ORGANOMETALLIC CHEMISTRY ON METALS - A NOVEL AND EFFECTIVE ROUTE TO CUSTOM-DESIGNED BIMETALLIC CATALYSTS

The synthesis, characterization and catalytic properties of new materi als obtained by reaction of organometallic complexes of groups IIb, IV a, and VIa with the surface of metallic particles are reviewed. Two ty pes of materials may be obtained by surface organometallic chemistry o n metals: metal particles covered with organometallic fragments, and b imetallic particles of predetermined composition. Characterization of the organometallic fragments on the metal particles has demonstrated t heir thermal stability. These particles covered with surface organomet allic fragments are new catalytic materials, highly selective in sever al reactions such as the hydrogenation of alpha,beta-unsaturated aldeh ydes, ethyl pyruvate, nitrobenzene, acrylonitrile, and olefins. The bi metallic particles without organometallic fragments are also highly ac tive and selective for a variety of reactions such as hydrogenolysis o f various alkanes and hydrogenolysis of esters. For these systems, the concept of ''site isolation'' has been advanced to account for the hi gh selectivity of the reactions.