Phosphine amine ligand

Several types of phosphine ligands that incorporate an amine base have been synthesized. As illustrated in the selected leading references, studies of the metal complexes of these ligands have shown that in some cases the base can participate in small-molecule activation and hydrogen bonding interactions.1-6 In one large class of mixed phosphine-amine ligands, prepared by Mannich-type reactions, a... 

The new phosphine amine ligand (486) has been developed for the Cu-catalysed Michael addition of vinyl alanes R2A1C(R )C=CR R to A-substituted-2,3-dehydro-4-piperidones. The reaction gave the expected products with <97% ee ... 

The organometalhc approach allows control of the surface. It is therefore possible to prepare species displaying a clean surface able to adsorb small molecules (CO, H2) or large Hgands (phosphines, amines, thiols, polyden-tate ligands, etc.). 

Thiols, Phosphines, Amines, and Silanes. With these ligands, ethanol addition clearly gives a precipitate that can be isolated and readily redispersed in toluene or any other non-polar solvent again. 

A comparison of several of the biphenylphosphine ligands has provided some insight into the mechanism of catalyst activation.168 The results of this study suggest that dissociation of the diphosphino to a monophosphino complex is an essential step in catalyst activation, which would explain why some of the most hindered phosphines are among the best catalyst ligands. This study also indicated that deprotonation of the amine ligand is an essential step. Finally, in catalyst systems that are based on Pd(II) salts, there must be a mechanism for reduction to the active Pd(0) species. In the case of amines, this may occur by reduction by the amine ligand. 

The THT ligand in [AuRX2(THT)] and in other complexes can be displaced easily for other neutral or anionic ligands (e.g., phosphine, amines, halide, etc.), and a wide variety of derivatives... 

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

Non-activated aryl bromides (but not fluorides) can be used as substrates for palla-dium(0)-catalyzed aromatic nucleophilic substitutions with aliphatic or aromatic amines. These reactions require sodium alcoholates or cesium carbonate as a base, and sterically demanding phosphines as ligands. Moreover, high reaction temperatures are often necessary to achieve complete conversion (Entries 7 and 8, Table 10.4 Experimental Procedure 10.1). Unfortunately, the choice of substituents on the amine... 

Addition of modifying ligands such as tributyl phosphine affords a one-step, cobalt-catalyzed synthesis of alcohols (at lower pressure), but accompanying olefin hydrogenation reduces yields (3). With amine ligands, the effects are varied. Accelerated hydroformylation rates are possible with weak bases such as pyridine, but stronger bases (piperidine or triethylamine, for example) retard or completely inhibit the reaction (4,5). 

A final example of shape selective catalysis is the selective hydrogenation of alkynes, alkenes and other hydrocarbons over Pd complexes anchored to montmorillonite clay supports.29 In these studies, phosphines and amine ligands were first reacted with montmorillonite and then reacted with palladium (II) salts to form anchored Pd(II) complexes in the interlamellar spacings of the montmorillonite clay. 

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