Premium
Chiral Diphosphine ddppm‐Iridium Complexes: Effective Asymmetric Imine Hydrogenations at Ambient Pressures
Author(s) -
Dervisi Athanasia,
Carcedo Cristina,
Ooi Liling
Publication year - 2006
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200505276
Subject(s) - iridium , chemistry , catalysis , imine , asymmetric hydrogenation , cationic polymerization , atmospheric pressure , hydrogen , inorganic chemistry , photochemistry , medicinal chemistry , polymer chemistry , organic chemistry , enantioselective synthesis , oceanography , geology
Complexes of the type [Ir(ddppm)(COD)]X were prepared and tested in the asymmetric hydrogenation of a range of imine substrates. Contrary to known iridium catalysts, the ddppm complexes formed efficient catalysts under an atmospheric hydrogen pressure, whereas at higher pressures the catalytic activity of the system was drastically reduced. Depending upon the reaction conditions, N ‐arylimines, Ar′NCMeAr, were hydrogenated to the corresponding secondary amines in high yields and enantioselectivities (80–94% ee). In contrast to the [BF 4 ] − and [PF 6 ] − complexes, coordinating anions such as chloride did not form active Ir‐ddppm hydrogenation catalysts. The cationic Ir‐ddppm hydrogenation system performed well in chlorinated solvents, whereas coordinating solvents deactivated the system. Dimeric and trimeric Ir(III) polyhydride complexes were formed from the reaction of [Ir(ddppm)(COD)]PF 6 with molecular hydrogen at atmospheric pressure and were found to inhibit catalytic activity.