| Abstract
| - The complex [Rh(cod)(dppp)]OTf (Rh(cod)) has been immobilized onto silica-supported palladium nanoparticles (Pd/SiO2) via a dual H-bond/ionic interaction (dppp = 1,3-bis(diphenylphosphino)propane; cod = cycloocta-1,5-diene). The product obtained, Rh(cod)-Pd/SiO2, has been employed to catalyze the hydrogenation of benzene to cyclohexane, showing much higher activity as compared to Pd/SiO2, while Rh(cod) grafted on bare silica (Rh(cod)/SiO2) is totally inactive. The catalyst generated by Rh(cod)-Pd/SiO2 exhibits a remarkable stability and can be recycled several times with no loss of activity, even if exposed to air. In situ and ex situ EXAFS and DRIFTS measurements, batch catalytic reactions under different conditions, deuterium labeling experiments, and model organometallic studies, taken altogether, have provided valuable mechanistic information. The reduction of benzene to cyclohexa-1,3-diene occurs with the cooperation of the two metals, while the rhodium single sites are more effective than the palladium nanoparticles in the hydrogenation of cyclohexa-1,3-diene to cyclohexane.
- The complex [Rh(cod)(dppp)]OTf (Rh(cod)) has been immobilized onto silica-supported palladium nanoparticles (Pd/SiO2) via a dual H-bond/ionic interaction (dppp = 1,3-bis(diphenylphosphino)propane). The Rh(cod)-Pd/SiO2 product has been employed as the catalyst precursor in the hydrogenation of benzene to cyclohexane, showing much higher activity as compared to Pd/SiO2. The combined action of the two metals activates the arene so as to allow the rhodium sites to enter the catalytic cycle and speed up the overall hydrogenation process.
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