In situ study of diphosphine rhodium systems in asymmetric hydroformylation of styrene

Abstract

HPNMR and in situ HPIR (HP = High Pressure) spectroscopic techniques were used to study the species present in the hydroformylation of styrene by rhodium disphosphine systems. Rhodium precursors with BDPP [(2S,4S)-bis(diphenylphosphino)pentane] and CHIRAPHOS [(2R,3R)-bis(diphenylphosphino)butane] as the chiral ligands (P–P) were used. The species observed were compared in order to find a relation between the structures and the enantiomeric excesses obtained for both chiral diphosphines. The effect of the P–P ∶ [Rh] molar ratio and the addition of a monophosphine on the enantiomeric excess were studied. It has been found that oxidation of the coordinated chiral diphosphine leads to formation of rhodium species more active but less regio- and enantio-selective.