Phosphines phosphite complexes

After the discovery of the high ee provided by rhodium/diphosphite and rhodium/phosphine-phosphite complexes, with total conversion in aldehydes and high regioselectivities, rhodium systems became the catalysts of choice for asymmetric hydroformylation. Important breakthroughs in this area have been the use of rhodium systems with chiral diphosphites derived from... 

The spectroscopic data of phosphine-phosphite complexes show slight differences between the (R,S) and (S,R) complexes on the one hand and the (R,R) and (S,S) complexes on the other. In the latter compounds the data are less clear-cut, which could be due to structural deviations of the monohydride complexes from an ideal trigonal bipyramid or to equilibria between isomers. The two ea isomers cannot be distinguished by IR spectroscopy as their absorptions tend to coincide [82],... 

The corresponding phosphine/phosphite complexes (169) may be made, in at least selected cases, from (163) by photolysis in the presence of the phosphine or phosphite in... 

Mixed phosphine-phosphite complexes Re(NPh)X3(PPh3)[P(OMe)3] can be obtained by the reaction of ReOX3(PPh3)[P(OMe)3] with aniline in refluxing benzene," while the mixed pyridi-... 

The [Rh(acac)(phosphine-phosphite] complexes were used as precursors for the asymmetric hydroformylation of styrene after adding 3 equivalents of free ligand. The results are shown in Table 3. The ee of the product decreases with increasing temperature. The ratio of CO to H2 does not affect the regio- and enantioselectivity. 

The coordination mode of the ligands in the [RhH(CO)2(phosphine-phosphite)] complexes has been studied using IR and NMR spectroscopy under 20 bar of CO/H2. The HP-IR spectrum shows the presence of a single species and HP-NMR spectroscopy shows that the phosphine and the phosphite occupy an apical and equatorial position respectively, as would have been expected from the donor and acceptor properties. This is in contrast with the coordination mode found for the [RhH(CO)2(phosphine-phosphite)] complex of BINAPHOS in which the phosphine occupies an equatorial position and the phosphite an apical position [49]. 

Nozaki, K. Sato, N. Takaya,H. Highly enantioselective alternating copolymerization of propene with carbon monoxide catalyzed by a chiral phosphine-phosphite complex of paUadinm(II). J. Am. Chem. Soc. 1995,117, 9911-9912. 

Also in the rhodium catalyzed hydroformylation of vinyl carbonates with biden-tate phosphine-phosphite complexes, the a-aldehyde was favored a/p = 92 8), which opens up the possibility of running the reaction in a stereoselective manner [41]. 

Mixed-phosphine-phosphite complexes behave in a similar manner (1417). 

Rubio M, Suarez A, Alvarez E et al (2005) Highly enantioselective hydrogenation of enol ester phosphonates catalyzed by rhodium phosphine-phosphite complexes. Chem Commun... 

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