Rhodium cationic complexes using macrocyclic diphosphines as chiral ligands:: Application in asymmetric hydroformylation

Abstract

The mononuclear complexes [Rh(COD)(OC n P)]BF 4 were prepared by adding 1,1′-binaphthyl-based diphosphine macrocyclic ligands (OC n P, n=4–6) to a dichloromethane solution of [Rh(COD) 2]BF 4 (COD=1,5-cyclooctadiene). Hydroformylation of styrene was carried out using solutions of rhodium-diphosphine catalyst prepared from [Rh(acac)(CO) 2] and chiral macrocyclic diphosphines OC n P, n=2, 4–6. At 30 bar of CO/H 2 (1:1) and 65°C regioselectivities in 2-phenylpropanal were >92% when all the chiral diphosphine was added in a PP/Rh ratio of 2. The solution structure of the dominant species formed during the reaction of [Rh(acac)(CO) 2] with (rac)-OC 6P under hydroformylation conditions has been determined.