Metal carbonyl clusters as precursors of heterogeneous catalysts: Hydrogenation and disproportionation of monoenes, dienes, and arenes in the presence of H2Ru4(CO)13, H2FeRu3(CO)13, and HRuCo3(CO)12 supported and activated on chromosorb. Characterization of the metal particles derived from H2Ru4(CO)13 by means of IR spectroscopy and TEM microscopy

Abstract

The tetrahedral hydridic clusters H2Ru4(CO)13 (1), H2FeRu3(CO)13 (2), and HRuCo3(CO)12 (3) were supported on Chromosorb P and activated under dihydrogen flow. The resulting metal particles are active in the hydrogenation of pentenes, cyclic monoenenes and dienes, benzene, and toluene; these catalysts are effective under mild conditions and with a low metal loading. Experiments under dinitrogen showed that complex hydrogenation-dehydrogenation processes occur, as already observed for the same clusters during the homogeneous hydrogenation of cyclohexadienes. After the gas-chromatographic catalytic runs with cluster 1 as precursor, TEM microscopy showed the presence of very small supported metal particles (mean size 7.5 nm). The decomposition of cluster 1 to metal particles upon thermal treatment on Aerosil under vacuum or under dihydrogen was followed by means of IR spectroscopy; this catalyst hydrogenates benzene at room temperature with 100% conversion in a very short time (calculated activity was about 3200 TOFs).