Rh rhodium complexes

Prochiral imines can be hydrogenated to the corresponding amines with extremely high enan-tioselectivities in H20/ethyl ethanoate biphasic systems, using Rh1 complexes of sulfonated phosphines 342 The cationic rhodium complex [Rh(NBD)(131)]+ was an active catalyst for hydrogenation of 2-ethanamido-propenoic acid in aqueous solution.343... 

Some of the hydroarylation product is also observed substituted anilines afford the two products to varying degrees (Equation (15)). The closely related rhodium complexes [Rh(PCy3)2Cl]2, [Rh(dmpe)Cl]2 (where dmpe= l,2-bis(dimethylphosphino)ethane), and [Rh(C8H14)Cl]2 show essentially no catalytic activity.166 Application of [Rh(PEt3)2Cl]2 to the reaction of aniline with styrene gives a mixture of hydroamination and oxidative amination products, the latter predominating.167 Other related rhodium-catalyzed amination reactions (oxidative amination) have been reported.168 169... 

A crucial achievement significantly stimulated the development of the investigation in the field of homogeneous enantioselective catalysis. The Knowles group established a method for the industrial synthesis of I-DOPA, a drug used for the treatment of Parkinson s disease. The key step of the process is the enantiomeric hydrogenation of a prochiral enamide, and this reaction is efficiently catalyzed by the air-stable rhodium complex [Rh(COD)((PP)-CAMP)2]BF4 (Scheme 1.12). 

Another type of chiral rhodium complex [Rh-MeDuPHOS] was also immobilized in [BMIM][PF6] and used in the enantiomeric hydrogenation of related enamides [95] (Fig. 41.5). Geresh et al. focused their research on the stabilization of the air-sensitive catalyst in the air-stable ionic liquid, so that the complex was protected from attack by atmospheric oxygen and recycling was possible. 

A series of studies deals with the catalytic activity of the dinuclear thiolate-bridged rhodium complex [ Rh( i-S Bu)(CO)(TPPTS) 2] in the hydroformylation ofpropene, 1-hexene and 1-octene (Scheme 4.4) [76-80]. Turnover frequencies up to 3100 h" were detected. 

The tetrasulfonated chiraphos reacts in water with [Rh(COD)Cl]2 in a ratio of 2 1 to give a rhodium complex [Rh(COD)(ChiraphosTS)]Cl1 [31P(DzO) S ppm 57.4 (d, JRh P = 148 Hz)] which catalyzes the enantioselec-tive reduction of amino acid precursors in a two-phase system of water-ethyl acetate with ee in the range 81-88%. 

Anionic polymerization of phenylacetylene to a trans-cisoid polymer in the presence of crown ether phase-transfer catalysts initiated by sodium amide has been reported.425 In contrast, the zwitterionic rhodium complex Rh+(COD)BPhJ yields a ds-transoid product in the presence of Et3SiH.426... 

Homogeneous hydrogenation catalyzed by the four-coordinated rhodium complex, Rh[(C6H5)3P]3Cl, has been particularly well investigated. With this catalyst, the first step is formation of the six-coordinated rhodium hydride of known configuration, 16, in which we abbreviate the ligand, triphenylphosphine, (C6H5)3P, as L ... 

Lehn and coworkers156,157 investigated the rhodium complex [Rh(bipy)3]3+, which on photolysis in solutions containing [Ru(bipy)3]2+, TEOA and K2PtCl4 produces hydrogen after a short induction period during which [PtCl4]2 is reduced to Pt° (see below). They found that an... 

Aryltrimethylstaimanes arylate aldehydes in the presence of a cationic rhodium complex, [Rh(cycloocta-l,5-diene)(MeCN)2]+, yielding secondary alcohols.114... 

A cationic rhodium complex, [Rh(COD)2]BF4-2PPh3, is a highly efficient catalyst for this reaction, which gives ( )-/-triethylsilylallyl alcohol (127) with complete /-selectivity... 

A kinetic study of the Rh-BINAP-catalysed 1,4-addition of phenylboronic acid using reaction calorimetry revealed that the catalytically inactive dimeric hydroxo- rhodium complex [Rh(OH) (/J)-BINAP ]2 (191) is the resting state (Scheme 6). A negative non-linear effect in eeprod and an amplified reaction rate were predicted and observed in the present reaction system that is characterized by the preferential formation of the homochiral (191) dimer.240... 

Step (1) involves the formation of methyl iodide, which then reacts with the rhodium complex Rh(I)L by oxidative addition in a rate-determining step (2) to form a methylrhodium(III) complex. Carbon monoxide is incorporated into the coordination sphere in step (3) and via an insertion reaction a rhodium acyl complex is formed in step (4). The final step involves hydrolysis of the acyl complex to form acetic acid and regeneration of the original rhodium complex Rh(I)L and HI. Typical rhodium compounds which are active precursors for this reaction include RhCl3, Rh203, RhCl(CO)(PPh3)2, and Rh(CO)2Cl2. 

The rhodium complex [Rh(acac) (C2Hi )2] reacts with the unsaturated triosmium compound to give the 60-electron cluster species [Rh0s3(y-H)2(y-acac)(CO)10J (A7) in which the acac ligand acts as a five-electron donor, one oxygen atom bridging an Os — Rh separation of 3.292(2) so that the four metal atoms adopt a butterfly configuration. 

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