Functional phosphanes Part X. Homogeneous hydration of ketones and alpha,beta-unsaturated carbonyl compounds with 2-(diphenylphosphanyl)anilido complexes of iridium and rhodium as catalysts - Molecular structure of [Rh(PPh3)(2)(2-Ph2PC6H4NH-kappa N,k

摘要

The catalytic hydrogenation of saturated and unsaturated ketones and aldehydes in the presence of [Ir(CO)(PPh3)(2-Ph2PC6H4NR-kappaN,kappaP)] (R = H: 1; R = Me: 2), [Rh(CO)(PPh3)(2-Ph2PC6H4NR-kappaN,kappaP)] (R = H: 3; R = Me: 4), [Rh(PPh3)(2)(2-Ph2PC6H4NH-kappaN,kappaP)] (5), and [Ir(CO)(PPh3)(2-Ph2PC6H4N{C(O)camph-(1S)}-kappaN,kappaP)] (6, C(O)camph-(1S) = (1S)-camphanoyl) has been investigated. Out of the complexes tried, only 1 showed significant activity for the reduction of the carbonyl group. Evidence is presented that the catalytic cycle is entered by the formation of the cis-(H,H)-cis-(P,P)-dihydride [IrH2(CO)(PPh3)(2-Ph2PC6H4NH-kappaN,kappaP)] (9a) which can be observed by H-1 NMR under 45 bar H-2. The homogeneous hydrogenation of five alpha, beta -unsaturated carbonyl compounds (crotonaldehyde, ethyl vinyl ketone, 2-cyclohexen-1-one, benzylideneacetone, and benzylideneacetophenone), in the presence of 1, proceeded with chemoselectivities for the corresponding allylic alcohols varying between zero for EtC(O)CH=CH2 and 77-78% for PhCH=CHC(O)Me and MeCH=CHCHO, respectively. Complexes 1 and 5 were fully characterized by X-ray structure analysis. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 38]