Green Synthesis of Rhodium Nanoparticles that are Catalytically Active in Benzene Hydrogenation and 1-Hexene Hydroformylation

Rhodium nanoparticles (Rh NPs) were prepared according to a green method based on the reduction of (acetylacetonato)dicarbonylrhodium(I), Rh(acac)(CO)(2), in water at 80 degrees C. The nanoparticles, which were obtained without the addition of a reducing agent, were stabilized by polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) polymers and characterized by TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), and XRD (X-ray powder diffraction) methods. The excellent catalytic activity of these Rh NPs was evidenced in the hydrogenation of benzene to cyclohexane. In the presence of PPh3, Rh NPs formed a highly active system in the hydroformylation of 1-hexene. In this system, they acted as a source of soluble rhodium species. Rh NPs were also synthesized in water using rhodium(II) acetate, Rh-2(OAc)(4), and rhodium(III) chloride, RhCl3, as rhodium sources, and their catalytic activity was compared with that of the rhodium precursors.