MIXED IRON-RHODIUM CARBIDOCARBONYL CLUSTERS ON OXIDE SUPPORTS - CHEMISTRY AND CATALYSIS OF SYN-GAS REACTIONS

Genesis of silica-supported [Fe5RhC(CO)(16)](-) and [Fe4RhC(CO)(14)](- ) clusters with interstitial carbon atoms have been investigated in CO , syn-gas and Ar media. Complete conversion of the former cluster to t he latter was obtained at 50 degrees C in any medium, with [Fe4RhC(CO) (14)](-) cluster yielding Fe4Rh2C(CO)(16) and [Fe3Rh3C(CO)(15)](-) mix tures at 100-150 degrees C. Simultaneously, Fe2+ ions emerged on the S iO2 surface. Mossbauer and electron microscopic studies on the silica- deposited clusters showed that at treatment in any medium in the range of 250-350 degrees C highly dispersed FeRh particles are located on t he silica surface, where Fe atoms exist mainly in the oxidized state e ven after H-2 reduction. Silica-supported catalysts derived from a fam ily of FeRh carbidocarbonyl clusters were found to exhibit increased a ctivity and selectivity toward oxygenates in CO hydrogenation and C3H6 hydroformylation compared to those of monometallic cluster-derived ca talysts. Possible explanations are discussed.