| Abstract
| - The combined application of two or more metals in homogeneous catalysis can lead to synergisticeffects; however, the phenomenological basis for these observations often goes undetermined. The hetero-bimetallic catalytic binuclear elimination reaction, a system involving both mononuclear and dinuclearintermediates, has been repeatedly suggested as a possible mechanism. In the present contribution, thesimultaneous application of Rh4(CO)12 and HRe(CO)5 as precursors in the hydroformylation reaction leadsto a very strong synergistic rate effect. In situ spectroscopic measurements confirm the presence of bothmononuclear and dinuclear intermediates such as RCORh(CO)4 and RhRe(CO)9 in the active system.Moreover, kinetic analysis confirms interconversion of these intermediates as well as their statisticalcorrelation with organic product formation. Specifically, the rate of hydrogen activation by RhRe(CO)9 isexactly equal to the rate of aldehyde formation from binuclear elimination between HRe(CO)5 and RCORh(CO)4 at all reaction conditions studied. Thus the catalytic events involving mononuclear species and thoseinvolving dinuclear species are synchronized. In the present experiments, the new topology is orders ofmagnitude more efficient than the corresponding unicyclic rhodium system.
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