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

HPNMR and in situ HPIR (HP = High Pressure) spectroscopic techniques were u sed to study the species present in the hydroformylation of styrene by rhod ium disphosphine systems. Rhodium precursors with BDPP [(2S,4S)-bis(dipheny lphosphino)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 excess es obtained for both chiral diphosphines. The effect of the P-P : [Rh] mola r ratio and the addition of a monophosphine on the enantiomeric excess were studied. It has been found that oxidation of the coordinated chiral diphos phine leads to formation of rhodium species more active but less regio- and enantio-selective.