Ligands chelating diphosphine

A water-soluble chelating diphosphine ligand (9) based on the xanthene backbone was also studied as supported aqueous phase catalysts. It was shown that this ligand performed well as SAPC since it is much more selective than other SAPC systems reported in literature [68]. Recycling experiments showed that these catalysts retained their activity and selectivity for at least ten consecutive runs, whereas under similar conditions the TPPTS based catalyst showed a reduced performance in the fourth run. 

Figure 6-3. Mechanism for the hydrogenation of a prochiral substrate methyl acet-amidocinnamate (MAC) with a catalyst containing a chiral chelating diphosphine ligand...

Figure 1. Diastereomeric catalyst-substrate adducts produced upon addition of olefin to solvated catalyst with chelating diphosphine ligand.

Since our first model system is achiral, we did not need to consider different diastereomeric manifolds. However, we did need to follow four different reaction pathways corresponding to the four possible cis -dihydride isomers (Figure 5). Intermediates with traits phosphorus orientations were not considered because the catalysts of interest have chelating diphosphine ligands. 

Scheme 8 Rhodium complexes of trans-chelating diphosphine ligands...

DR. GEOFFROY We obviously don t know why the photochemistry changes. We know that it is reasonable that phosphine dissociation does not occur when we have a chelating diphosphine ligand. But we don t understand why we see hydrogen loss in this system when we don t see it in the other cases. 

While apparently no metallasilsesquioxane complexes of nickel and palladium have yet been prepared, several literature reports have appeared on platinum compounds containing silsesquioxane ligands. Abbenhuis reported the synthesis and characterization of three platinum(II) complexes stabilized by the chelating diphosphine ligand dppe (= 1,2-bis(diphenylphosphino)ethane) as outlined in Scheme 63. ... 

Alternating copolymerization of carbon monoxide with ethene was discovered in the early 1950s [112] and has been attracting much interest lately. Among the several metals such as, Ni(II), Pd(II), and Rh(I) that can promote this reaction [113], Pd(II) complexes with a cis-chelating diphosphine ligand and a non-coordinating counter anion were selected as the catalysts of choice and have been studied extensively [114,115]. 

The Effect of Chelating Diphosphine Ligands on Homogeneous Catalytic Decarbonylation Reactions Using Cationic Rhodium Catalysts... 

The reaction of alkyl halides with (rans-[M(N2)2(diphos)2] (diphos = chelating diphosphine ligand) can give rise to dialkylhydrazido(2-) complexes via the alkyldiazenido species (76, 93, 94) [Eqs. (37) and (38)1. 

In contrast, some rr- allyl ruthenium complexes containing a chelating diphosphine ligand were the first metal complexes which favoured the anti-Markovnikov addition of carboxylic acids to terminal alkynes to form (Z)-enol and (E)-enol esters with high regioselectivity and stereoselectivity [17-19] according to Eq. (1). 

Binding of Chelating Diphosphine Ligands to Cp-rutheninm Systems... 

Introduction. DIOP was the first example of a C2 chelating diphosphine for transition metal complexes to be used in asymmetric catalysis. It was also one of the first examples of a useful C2 chiral auxiliary. DIOP can be considered as an example of the first generation of chelating diphosphine ligands with a chiral carbon skeleton, which were followed over the next 20 years by many examples of chelating diphosphines, one of the most efficient of which is BINAP [2,2 -Bis(diphenylphosphino)-l,l -binaphthyl] The ready availability of DIOP has stimulated research in asymmetric catalysis beyond the area of asymmetric hydrogenation. 

Two polyhydrido iridium clusters with chelating diphosphine ligands are prepared by the reaction of [Ir(dppp)(cod)] [BF4] with hydrogen in a methanol solution. These compounds are formulated as [Ir3(dppp)3H7][BF4]2. 1. attd [Irz(dppp)2H5][BF4], 2. Their structures... 

The development of supported aqueous-phase catalysis (SAPC) [275, 276] is a new and efficient way to facilitate the hydroformylation of longer olefins. Most of the SAP catalysts described in the literature use TPPTS as ligand. Only a few sulfonated diphosphine ligands were examined [277]. A water-soluble chelating diphosphine ligand with a wide natural bite angle, based on a xanthene backbone, was studied as a SAP aqueous catalyst. This ligand showed a much better selectivity than the SAP catalysts known so far [278]. 

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