Amines phosphorus ligands

Nitrogen ligands with tetracoordinated nitrogen atoms amines Phosphorus Ligands... 

A non-covalently functionalized dendrimer was also applied in a continuous allylic amination reaction.[33] PPI dendrimers functionalized with urea adamantyl groups can act as host molecules for phosphorus ligands equipped with acetyl urea groups (Figure 4.18). The so formed supramolecular complex was reacted with a palladium precursor... 

Because of its potential application to the synthesis of estersfor lubricating oils, the dimerization-carbonylation of butadiene has received special attention. Basic phosphines such as PBun3 and weakly basic tertiary amine solvents (quinoline, N, N-diethylaniline) were found to improve both the stability and activity of the catalyst system.S3° In a further report in which PPr 3 was used as phosphorus ligand it was found that the addition of maleic anhydride caused a marked increase in the catalytic activity. It was believed that through coordination it stabilized the palladium(O) complexes formed against precipitation as metal.s 1... 

If carbanions are to be titanated, alkoxy or amino ligands at titanium are most likely to ensure success. Sulfur or phosphorus ligands have not been tested. In rare cases electrontransfer instead of titanation sets in, forming Ti(III) species which are generally unsuitable for useful chemistry. This is most likely to occur if the carbanion is very electron rich, e.g., in case of dianions or extended anionic K-systems. We have noticed that this undesired property decreases in going from chloro to alkoxy and finally to amino ligands at titanium. For example, dianions derived from carboxylic acids reduce chlorotitanium triisopropoxide 3 to some extent, whereas quantitative double titanation occurs with chloro- or bromotitanium tris(diethylamide) 15 77>. Addition of amines to the reaction mixture has similar effects 77). 

Rh and Ir complexes stabilized by tertiary (chiral) phosphorus ligands are the most active and the most versatile catalysts. Although standard hydrogenations of olefins, ketones and reductive aminations are best performed using heterogeneous catalysts (see above), homogeneous catalysis becomes the method of choice once selectivity is called for. An example is the chemoselective hydrogenation of a,/ -unsaturated aldehydes which is a severe test for the selectivity of catalysts. 

The mechanism of the amination reactions of 1,3-dienes assisted or catalyzed by nickel and palladium species has often not been elucidated. Catalysts prepared from nickel or palladium salts or complexes, Lewis acids, and phosphorus ligands were all used since amine telomers are mainly produced, it is plausible that zr-allyl complexes are the reactive intermediates21 24. The reaction carried out with amine hydroiodide or hydrochloride, or in the presence of trifluo-roacetic acid, is presumed to proceed via the following mechanism24 25. 

By introducing different amines into an organic solvent such as toluene the sodium cations of the sulfonates can be exchanged by addition of sulfuric acid. Sodium hydrogensulfate is formed as a by-product. As immobilized phosphorus ligand TPPTS is used in most cases. 

With respect to succeeding membrane separation it was found that generally an increase of the molecular mass of the amines leads to improved retention of rhodium, of phosphorus ligand and, last but not least, of the amines. It can be demonstrated that an increase in molecular mass does have a contradictoryeffect on the overall efficiency. A high amount of permeate corresponds to a lower flux of permeate due to the higher concentration of compounds within the retentate (osmotic pressure). Traces of amine in the permeate are the result of a very low temperature-dependent dissociation of the ammonium salts into amine and free acid according to eq. (7). 

This chiral diene ligand displays a clear superiority over chiral phosphorus ligands in both enantioselectivity and catalytic activity. A second generation catalytic system tvas later reported for the highly enantioselective addition to N nosyl imines, for which the product is more easily converted into the free amine than that bearing a N tosyl group [120]. The more effective chiral ligand 60 had to be used (Scheme 1.36). 

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