Formation of bimetallic RhCo3 clusters from monometallic carbonyl clusters on SiO2 as probed by hydroformylation

A bimetallic SiO2-supported RhCo3 cluster catalyst derived from Rh-4(CO)(12) and Co-2(CO)(8) by coimpregnation followed by decarbonylation under H-2 at 623 K has been probed by atmospheric ethylene hydroformylation at 423 K. The catalytic behavior is consistent with that of RhCo3/SiO2 derived from RhCo3(CO)(12). At the same time, the corresponding binary catalysts prepared from inorganic rhodium and cobalt salts exhibit much lower activities than RhCo3/SiO2 and significantly enhanced activities compared to monometallic catalysts. The results suggest that the increase in catalytic activity by combination of rhodium and cobalt is attributed to the bimetallic catalysis by RhCo3 clusters regardless of the synergistic catalysis by monometallic rhodium and cobalt sites. (C) 1997 Elsevier Science B.V