Ferrocenyl-phosphine-rhodium complexe

Cullen, W. R., and E-Shan Yeh Asymmetric Hydrogenation Using Ferrocenyl-phosphine Rhodium(I) Cationic Complexes. J. Organomet. 139, C13 (1977). 

For asymmetric hydrosilylation of ketones a rhodium complex coordinated with the ferrocenyl(dimethyl)phosphine 3b has been reported to be more effective than other ferrocenylphosphines to give optically active alcohols (up to 49% ee) after hydrolysis (Scheme 2-49) [7]. 

More recently, a rran.y-chelating asymmetric ferrocenyl phosphine (abbreviated as TRAP) has been developed [63]. The rhodium complex of TRAP catalyzes asymmetric Michael additions of a-cyanocarboxylates in high enantioselectivity (72-89 % ee) (eq (18)) [64]. Because these Michael reactions proceed via a A -bound enolato complex [65], the reaction center on the enolato ligand is far from the metal center. Thus, a CLv-chelating phosphine cannot control the direction of electrophilic attack. The reaction with c/.y-chelating phosphines gives only a poor enantiomeric excess (BINAP, 17 % ee DIOP, 12 % ee CHIRAPHOS, 3 % ee). 

A bimetallic Rh-Re catalyst (9) is effective for related hydrogenations shown in equation (16) that works best if R = R = H (ee 82-98%). The X-ray structure of the racemic complex was determined. Chiral derivatives of the more familiar ferrocenyl phosphines are effective in the rhodium-catalyzed hydrogenation of... 

Complexes of different dendrimers with rhodium that contained ferrocenyl phosphine ligands on the surface, 52-53, were also active in hydrogenation. They catalyzed dimethylacetone hydrogenation at an optical selectivity of 98%, which is comparable to the selectivity of a low molecular weight analogue [113, 123, 124]. 

Enantioselective transfer hydrogenation (from propan-2-ol) of some ketones catalysed by iridium(i) complexes with chiral Schifl-base ligands has been reported, giving product alcohol of up to 33% e.e. with propiophenone as substrate. Other new reductive routes to chiral secondary alcohols involve the asymmetric hydrogenation of enol phosphinates (21) catalysed by chiral ferrocenyl-rhodium... 

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