Ligand phosphine-rhodium complex

Direct addition of VI to chlorocarbonylbis(phosphine)rhodium complexes containing more basic phosphine ligands to yield optically active complexes of the type III did not occur. An optically active benzylrho-dium complex (X) was obtained, however, by adding (S)a-trifluoro-methylbenzylchlorosulfite (IX) to chlorocarbonylbis (diethylphenylphos-... 

Figure I. Ligand exchange is a proposed key step in the mechanism of phosphine-rhodium complex catalyzed hydroformylation of olefins...

Advances in Chemistry, Editors Alyea, E. C., and Meek, D. W., American Chemical Society, 1981, 196, 78, paper of "31p NMR Studies of Equilibria and Ligand Exchange in Triphenyl phosphine Rhodium Complex and Related Chelated Bis-Phosphine Rhodium Complex Hydroformylation Catalyst Systems," by Kastrup, R. V., Merola, J. S., and Oswald, A. A., in press. 

Introduction Catalytic hydrogenation with soluble catalysts Hydrogenation with C2-Symmetrical ftis-Phosphine Rhodium Complexes C2 symmetric ligands (DIPAMP, DIOP, PNNP)... 

The hydrido phosphine rhodium complexes possess a relatively large negative charge on the hydrido ligand, and as such these compounds are not good catalysts for isomerization. Also, the rate of this reaction is influenced negatively by steric repulsion between phosphine molecules and the isoalkyl ligand in the intermediate compound [structure (13.59)]. 

Another very useful alternative is to promote the deprotonation of the imida-zohum salt by the addition of external bases, usually under refluxing conditions [32]. Once the carbene is generated, it reacts with the metal complex to produce the corresponding metal-carbene complex. In general, polar aprotic solvents, for example, THF, are used, and the reaction is run at room temperature. Carbenes can also displace a phosphine ligand in the Wilkinson complex [33]. Other phosphine-rhodium complexes can be likewise employed [34]. 

Bulky ortlio-methylated phosphine-ligand-coordinating rhodium complex 215 was used for enantiocontroUed and diastereocontrolled cyclopropanation with styrene (Scheme 1.98) [150]. The diastereoselectivity and enantioselectivity of the reaction depended on a substituent on the aromatic ring of the hgand. 

Rhodium complexes with oxygen ligands, not nearly as numerous as those with amine and phosphine complexes, do, however, exist. A variety of compounds are known, iucluding [Rh(ox)3] [18307-26-1], [Rh(acac)3] [14284-92-5], the hexaaqua ion [Rh(OH2)3] [16920-31 -3], and Schiff base complexes. Soluble rhodium sulfate, Rh2(804 )3-a H2 0, exists iu a yellow form [15274-75-6], which probably coutaius [Rh(H20)3], and a red form [15274-78-9], which contains coordinated sulfate (125). The stmcture of the soluble nitrate [Rh(N03)3 2H20 [10139-58-9] is also complex (126). Another... 

In 1968 Wilkinson discovered that phosphine-modified rhodium complexes display a significantly higher activity and chemoselectivity compared to the first generation cobalt catalyst [29]. Since this time ligand modification of the rhodium catalyst system has been the method of choice in order to influence catalyst activity and selectivity [10]. 

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