Chemical phosphorus ligands

Hydroformylation has been extensively studied since it produces optically active aldehydes which could be important precursors for pharmaceutical and fine chemical compounds. Thus, asymmetric hydroformylation of styrene (Scheme 27) is a model reaction for the synthesis of ibuprofen or naproxen. Phosphorus ligands were used for this reaction with excellent results, espe-... 

The development of chiral phosphorus ligands has made undoubtedly significant impact on the asymmetric hydrogenation. Transition metal catalysts with efficient chiral phosphorus ligands have enabled the synthesis of a variety of chiral products from prochiral olefins, ketones, and imines in a very efficient manner, and many practical hydrogenation processes have been exploited in industry for the synthesis of chiral drugs and fine chemicals. 

In the phosphole series (2), two phosphorus ligands are incorporated into a five membered ring. This had the effect of increasing 6P° (13.49), which was expected, and decreasing the slope (2.26), reflecting a decrease in the sensitivity of the chemical shifts to the electronic changes. 

In contrast to the tricarbonyl halide complexes, it is the exo conformation of () -allyl)FeCp(CO) complexes (163) which is preferred, and at equilibrium only traces of the endo isomer can be observed. Existing crystal structures of members of this class are of the exo conformation.Reasonable percentages of the endo conformer are realized upon low-temperature photolyses of their () -allyl)Fp precursors, however, and the activation barrier to endolexo conversion has been determined to be AG = 100.8kJmol for the 2-methallyl complex. In addition, the anti isomers, which can be prepared stereospecifically from the (j7 -allyl)Fp complexes, isomerize to the syn isomers with brief heating. The Fe NMR spectra are known for several of the complexes where CO has been replaced by a phosphine or phosphite (145) the chemical shift is highly dependent on the nature of the phosphorus ligand. ... 

Chemical shifts in the palladium (127) and platinum (131) mono-(hexafluoroacetone) complexes [256] are almost independent of the metal or of the other ligands, and very similar values are reported for the hexafluoroisopropylidineimine complex [257]. (131) The difference between the coupling of the CF3 groups to phosphorus ligands in the cis and trans positions, however, is notably larger for the platinum complexes than for those of palladium. 

In fact, in Sect. 7.1 we will encounter a set of equations with which we can calculate the chemical shift of the coordinated phosphorus ligand... 

An interesting array of phosphorus ligands is realized by species where the phosphorus atoms are bonded only to metal or phosphorus atoms. They carry no substituents and are called naked phosphorus . Their chemical shift values cover a very... 

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