In situ study of diphosphine rhodium systems inasymmetric hydroformylationof styrene

摘要

HPNMR and in situ HPIR (HP = High Pressure) spectroscopic technqiues were used tostudy the species present inthe hydroformylationof 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) wre used. The species observe were compared inorder to find a relation between the structures and the enantiometric excesses obtained for both chiral diphosphines. The effect of the P-P: [Rh] molar ratio and the addition of a monophosphine on the enantometric excess were studied. It has been found that oxidation of the coordinated chiral diphosphine leads toformationof rhodiumspecies more active but less regio- and enantio-selective.