Hybrid P-N phosphines as participative ligands in iridium hydrogenation catalysts

Article abstract of DOI:10.1016/0022-328X(91)80170-O

Iridium complexes formed in situ from 2 and a potentially bidentate ligand such as P(ο-C6H4NH2) Ph2 (= P-NH2) or P(ο-C6H4NMe2)Ph2 (= P-NMe2) catalyze the chemoselective hydrogenation of benzylideneacetone.In the presence of HIr(P-NH)2(P-NH2) the substituted allylic alcohol is obtained in 92percent yield, whereas in the presence of H2Ir(P-NMeCH2)(P-NMe2) there is a much poorer selectivity.The features of the catalysis are discussed in relation to the nature of the iridium species formed; steric factors appear to play a crucial role in determining the selectivity.Monitoring of the progress of the reaction catalyzed by the Ir/P-NH2 system by NMR spectroscopy has revealed the sequence of reactions, including ready intramolecular N-H activation.Yhe crystal structure of Ir(P-NH2)3 has been determined.