Study of the influence of PPh3 used as capping ligand or as reaction modifier for hydroformylation reaction involving Rh NPs as precatalyst

Author(s)

Garcia, Marco A. S. ; Ibrahim, Mahmoud ; Costa, Jean C. S. ; Corio, Paola ; Gusevskaya, Elena V. ; dos Santos, Eduardo N. ; Philippot, Karine ; Rossi, Liane M.

• Document type: Journal article
• Source: APPLIED CATALYSIS A-GENERAL; v. 548, p. 7-pg., 2017-11-25.

Abstract

The presence of capping ligands on the surface of metal nanoparticles (NPs) has been recognized to be a key factor for the control of their size and shape as well as for their stabilization, but their influence on the NP behavior in catalysis is far from being well-understood. Here, we investigated the performance of Rh NPs stabilized by tetraoctylammonium bromide (Rh-TOAB NPs) when applied as precatalyst for hydroformylation reaction. An ehnancement of the catalytic activity was clearly observed after adding monophosphines as a reaction modifier. More interestingly, a much higher effect was observed when a phosphine was directly used as capping ligand for the synthesis of the Rh particles, Le. in the absence of TOAB. Indeed, triphenylphosphine-stabilized Rh NPs (Rh-PPh3 NPs) were found to be a unique precursor for hydroformylation active catalytic species, leading to higher activity attributed to the existence of a strong phosphine-rhodium interaction in this case. The Rh-PPh3 NPs appeared less affected when adding poisoning ligands in catalytic reaction than the Rh-TOAB NPs PPh3 system which deactivates in the presence of CS2. In addition, a large excess (20 equiv. per Rh atom) of PPh3 was necessary to activate the Rh-TOAB NPs, similarly to the amount typically used in homogeneous catalytic systems. In the contrary, one equiv. of PPh3 (per Rh atom) was enough to prepare Rh-PPh3 NPs, which are more active and more stable against CS2 poisoning. All together our results evidence that a direct interaction of PPh3 ligand at the surface of Rh NPs plays an important role on their behavior in hydroformylation catalysis. (AU)

• FAPESP's process: 14/15159-8 - Metal nanoparticles: challenges on the preparation, stabilization and activation for catalysis
• Grantee: Liane Marcia Rossi
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/13119-3 - Vibrational spectroscopy in condensed phases
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants