A heterogeneous Rh/CPOL-BINAPa&PPh3 catalyst for hydroformylation of olefins: chemical and DFT insights into active species and the roles of BINAPa and PPh3

Abstract

Porous organic polymers (CPOL-BINAPa&PPh₃ and CPOL-BINAPa&PhPh₃) were synthesized via copolymerization of a divinyl-functionalized phosphoramidite ligand (2vBINAPa) and various trivinyl-monomers (3vPPh₃ and 3vPhPh₃). After metalation with Rh(acac)CO₂, Rh/CPOL-BINAPa&PPh₃ showed the better catalytic performance than Rh/CPOL-BINAPa&PhPh₃ in the heterogeneous hydroformylation. A corresponding catalytic Rh–H species has been investigated by FT-IR and/or NMR spectroscopy. The results indicated that two kinds of Rh–H species were formed in the Rh/CPOL-BINAPa&PPh₃ catalyst. The ee species containing the BINAPa ligand contributed to the high activity in hydroformylation. The three P coordinated Rh–H species consisting of BINAPa and PPh₃ ligands resulted in the high regioselectivity owing to the steric hindrance. Furthermore, the DFT calculations and cycle test results of the catalysts indicated that the PPh₃ moieties could improve the stability of the Rh–H species, prevent dissociation of Rh from the BINAPa moieties and reduce the loss of Rh in the catalytic process.