HYDROFORMYLATION OF STYRENE CATALYZED BY RHODIUM COMPLEXES WITH 2-DIPHENYLPHOSPHINOPYRIDINE

Mono- and binuclear rhodium complexes containing 2-(diphenylphosphino)pyridine, Ph2PPy 2, as ligand have been examined as catalysts for the hydroformylation of styrene. All the species tested were good catalysts and the formation of the expected aldehydes took place selectively within several hours in mild conditions. The binuclear derivative [(eta-5-C5H5)Rh2(mu-CO)(mu-Ph2PPy)(CO)Cl], 1, was an efficient catalyst only when the reaction was carried out under high pressure, whereas the in situ system obtained by addition of Ph2PPy to RhH(CO)(PPh3)3, 4, displayed a pronounced activity even in the low pressure reaction. P-31{H-1} NMR shows that in solution Ph2PPy can easily displace one or two moles of PPh3 from 4, giving rise to mixed mononuclear phosphine-rhodium complexes that seem likely to be the most active catalytic species.