Biarylphosphonites: a class of monodentate phosphorus(iii) ligands that outperform their chelating analogues in asymmetric hydrogenation catalysis

Rhodium(I) complexes of monodentate phosphonites derived from 2,2′-binaphthol and 9,9′-biphenanthrol are compared with diphosphonite chelate analogues as catalysts for asymmetric hydrogenation; the high ee’s (up to 92%) obtained with the monodentate systems and the observation that they are sometimes superior to the chelate analogues are discussed.