TPPTS ligand

At the same time, Schmidtchen et al. compared cationic phosphine ligands containing the hydrophilic guanidinium (4.3, 4.4) and the anionic phosphine ligand TPPTS for this palladium-catalyzed coupling reaction. They found that the cationic ligands were effective for the coupling reaction but less efficient than TPPTS 43... 

By using the more water-soluble ligand, TPPTS, Grosselin et al. converted several unsaturated aldehydes into the corresponding unsaturated... 

In a somewhat different approach, supported-aqueous-phase-catalysts (SAPC, see Chapter 5, Section 5.2.5 of this book) have been combined with supercritical CO2 in catalytic hydrogenation [55], Ruthenium was supported on silica and combined with the ligand TPPTS in water, after which a scC02/H2 phase was applied together with the substrate. Better levels of conversion were obtained using scC02 than the equivalent system with toluene for the hydrogenation of cinnamaldehyde. 

The water-soluble ligand (TPPTS) was discussed earlier with regard to aldehyde reduction [17]. Similarly, in ketone transfer hydrogenation, high yields are obtained for a variety of substrates with the ability for efficient catalyst recycling at no expense of activity or selectivity (Fig. 15.10). 

In 1986 a new process came on stream employing a two-phase system with rhodium in a water phase and the substrate and the product in an organic phase. For propene this process is the most attractive one at present. The catalyst used is a rhodium complex with a sulphonated triarylphosphine, which is highly water-soluble (in the order of 1 kg of the ligand "dissolves" in 1 kg of water). The ligand, tppts (Figure 8.6), forms complexes with rhodium that are most likely very similar to the ordinary triphenylphosphine complexes (i.e. RhH(CO)(PPh3)3). 

A breakthrough in the hydroformylation of propene was achieved following the synthesis of the water soluble ligand tppts for the preparation of the RhH(CO)(tppts)3 catalyst345 which formed the basis for the development of the Ruhrchemie/Rhone-Poulenc two phase process. This process operates under mild reaction conditions giving excellent n/i ratios and easy separation of products from the catalyst by decantation with virtually no catalyst leaching. 

The lifetime of the rhodium precatalyst depends on the rate at which the metal complex HRh(CO)(TPPTS)3 and the excess ligand TPPTS undergo decomposition. The catalyst lifetime is considerably increased by occasional addition of extra ligand. In general an increase in the reaction temperature and/or CO pressure results in a decrease in the catalyst lifetime. 

In the course of introducing the immobilized ligand TPPTS (triphenylphosphine trisulfonate) on an industrial production scale it was found that cations, especially ammonium and ammonium derivatives, have an extreme influence on the properties of the TPPTS salts. Even slight variations within the cations have a tremen-... 

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. 

The Mizoroki-Heck reaction was carried out in water/scCOz and ethylene glycol /scC02 using the typical sulfonated triphenylphosphine ligand TPPTS [56]. The reaction is claimed to occur under monophasic conditions although this seems unlikely under the C02 pressures and temperatures with the amounts of catalyst and co-solvent employed. Catalyst recycling was achieved by phase separation after... 

The thermal instability of rhodium-based hydroformylation catalysts has already been overcome commercially in the Ruhrchemie/Rhone-Poulenc process for propene hydroformylation in which the sodium salt of a sulfonated triphe-nylphosphine ligand (TPPTS, la) is used to solubilize the catalyst in the aqueous phase. In this process, the second phase is toluene and the reaction is carried out as a batch process with rapid stirring to intimately mix the two immiscible phases. After reaction, the system is allowed to separate and the organic phase is simply decanted from the aqueous catalyst phase. Both water-soluble polymers and PAMAM dendrimers have been reported as supports for rhodium-catalyzed hydroformylation under aqueous biphase conditions, but reactivities and regioselec-tivities were only comparable to or worse than those obtained with the reference TPPTS ligand. The aqueous biphase approach has found limited application for the hydroformylation of longer-chain alkenes, because of their very low solubility in water leading to prohibitively slow reaction rates, but there have been a variety of approaches directed at the solution of this problem. 

Due to the great solubility in water of the ligand TPPTS and the rhodium complex [HRh(CO)(TPPTS)3)j, it has been considered from the beginning that the hydroformylation reaction was occurring in the bulk of the aqueous phase [6]. In addition, the presence... 

This concept has also been demonstrated in reverse for the hydroformylation of a water-soluble olefin (aUyl alcohol) with the organic phase containing a catalyst, H Rh (CO) (P Ph3)3. In this case, the catalyst is present in the organic phase, whereas the catalyst-binding ligand (TPPTS) is added to the aqueous phase. 

Like every technically used and therefore real catalyst, the complex HRh(CO)-(TPPTSjj and the excess ligand TPPTS undergo a degree of decomposition that determines the catalyst s lifetime as measured in years. The catalyst deactivation mechanism is known in detail and depicted in Scheme 1 [5]. 

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