Ligands TPPMS

The results show that basic alkylphosphines are especially suitable. The ligand should be sterically demanding, but tri-f-butylphosphine (entry 8) is obviously too bulky. An ideal ligand seems to be tri-f-propylphosphine (entries 6 and 7). Unfortunately, the water-soluble ligands TPPMS (entries 2 and 3) and TPPTS do not work in this reaction, also the carbene ligand bis(mesitylene)imidazolium chloride (entry 12) has only a low activity. The influence of additives like maleic anhydride (MA) and 1,3-divinyltetra-methyldisiloxane (dvds) is negligible. 

Due to these reasons both in the early attempts in academic research and in the first successful industrial process in AOC sulfonated phosphines were used as ligands (TPPMS and TPPTS, respectively). A detailed survey of the sulfonated ligands is contained in Table 1 and in Figures 1-5. 

Several processes for the hydroformylation of higher alkenes have been suggested on the basis of the water-soluble ligand TPPMS. In contrast to TPPTS, which is almost exclusively soluble in water, TPPMS can be used in both aqueous and polar organic media. 

A variety of gold(I) complexes containing the water-soluble phosphine ligands TPPMS, TPPDS, and TPPTS were found active catalysts for the hydration of phenylacetylene to acetophenone in aqueous media. The isolated [Au(C=C Bu)(TPPTS)] showed a very high activity (1000 h ) at refiux temperature in methanol/water 5 1 in the presence of 10 mol% H2SO4 as cocatalyst (224). Similarly, various water-insoluble [AuBralNHC)] (225) and water-soluble [AuCl(NHC)] complexes (226) were effective in hydration of various terminal alkynes to the corresponding 2-oxo-derivatives. 

The reduction of allylic halides or acetates, as well as benzyl halides, can be achieved by the Pd-catalyzed reaction with formate ions in the biphasic system of toluene-water or heptane-water in the presence of hydrophilic phosphine ligands TPPMS, sodium 3-(diphenylphosphino)benzoate, and PEG-modilied trialkylphosphine. The process is accelerated by the addition of PEGJ ... 

A review on the use of ionic liquids in hydroformylation was authored by Hau-mann and Riisager in 2008 [92]. The first attempt dedicated to hydroformylation can be traced back to a publication of Chauvin etal. in 1996 [93]. They transformed 1-pentene into hexanal with a PPhg-modified rhodium catalyst in [BMlM][PFg] (Scheme 7.15). The replacement of PPhg by sulfonated phosphine ligands (TPPMS or TPPTS) lowered the activity of the catalyst but allowed a more complete recovery of the catalyst after the reaction. In general, low -regioselectivities resulted. 

Water-soluble phosphine ligands TPPMS, TPPDS, and TPPTS (mono-, di-, and tri-sulfonated triphenylphosphine, respectively) were tested as ligands for the hydration of aUcynes in aqueous media [116]. Complexes 19 and 20 (Fig. 1) gave the highest turnover frequencies ever reported (1,000 and 1,060 h , respectively) for the hydration of phenylacetylene under optimum conditions (0.1 mol% catalyst loading, 10 mol% H2SO4, reflux, and MeOH/H20). 

The use of water-soluble ligands was referred to previously for both ruthenium and rhodium complexes. As in the case of ruthenium complexes, the use of an aqueous biphasic system leads to a clear enhancement of selectivity towards the unsaturated alcohol [34]. Among the series of systems tested, the most convenient catalysts were obtained from mixtures of OsCl3 3H20 with TPPMS (or better still TPPTS) as they are easily prepared and provide reasonable activities and modest selectivities. As with their ruthenium and rhodium analogues, the main advantage is the ease of catalyst recycling with no loss of activity or selectivity. However, the ruthenium-based catalysts are far superior. 

Hydrogenation reactions in water have been extensively studied and many of the water-solubilizing ligands described in Chapter 5 have been tested in aqueous-organic biphasic hydrogenation reactions. One of the earliest catalysts used was the water-soluble analogue of Wilkinson s catalyst, RhCl(tppms)3 (tppms = monosulfonated triphenylphosphine), but many other catalysts have since been used including [Rh(cod)(tppts)2]+, [Rh(cod)2]+ and [Rh(acac)(CO)2]+ (cod = cyclooctadiene). 

A ligand with great potential for hydroformylation of higher, terminal alkenes is monosulfonated triphenylphosphine, tppms, that was studied by Abatjoglou, also at Union Carbide [12] (section 8.2.6). In this system hydroformylation is carried out in one phase that is worked up afterwards by adding water, which gives two phases to separate catalyst and product. 

Ligand design for fine chemical applications has been very limited and usually the ligands designed for large-scale applications are also tested for more complicated organic molecules. Tpp has been the workhorse in fine chemicals hydroformylation ever since Wilkinson s first examples [21,22], but also bulky phosphite [5], tppts and tppms [23] turned out to be very useful, and also diphosphites have been studied [24],... 

To avoid difficulties with the low solubility of Pd/TPPTS the monosul-fonated triphenylphosphine (TPPMS) was used as the ligand, which is less polar than the trisulfonated TPPTS. With the following solvents s3 a homogeneous phase is obtained DMF, DMSO, PEG 400 and isopropyl alcohol. A smaller amount of the mediator is required if TPPMS is used than with TPPTS as the hgand. hi further experiments the use of polyethylene glycol... 

As a polar solvent for the catalyst ethylene carbonate (EC), propylene carbonate (PC) and acetonitrile were used. Tricyclohexylphosphine, triphenyl-phosphine and the monosulfonated triphenylphosphine (TPPMS) were investigated as ligands with Pd(acac)2 as the precursor. Cyclohexane, dodecane, p-xylene and alcohols (1-octanol, 2-octanol and 1-dodecanol) were tested as non-polar solvents for the product. To determine the distribution of the product and of the catalyst, the palladium precursor and the hgand were dissolved in the polar solvent and twice as much of the non-polar solvent was added. After the addition of 5-lactone, the amounts of the product in both phases was determined by gas chromatography. The product is not soluble in cyclohexane and dodecane, more than 99% of it can be found in the polar catalyst phase. With the alcohols 1-octanol, 2-octanol and dodecanol about 50 to 60% of the 5-lactone are located in the non-polar phase. With p-xylene biphasic systems can only be achieved when EC is used as the polar solvent and even in this solvent system one homogeneous phase is formed at a temperature higher than 70 °C. In a 1 1 mixture of EC and p-xylene about 50 to 60% of the product is contained in the polar phase. 

TPPMS in EC, PC and acetonitrile, no further experiments were performed with this ligand. 

Unfortunately, for all these reasons the conclusions cannot be applied quantitatively for description of the pH effects in the RCH-RP process. There are gross differences between the parameters of the measurements in [97] and those of the industrial process (temperature, partial pressure of H2, absence or presence of CO), furthermore the industrial catalyst is preformed from rhodium acetate rather than chloride. Although there is no big difference in the steric bulk of TPPTS and TPPMS [98], at least not on the basis of their respective Tolman cone angles, noticable differences in the thermodynamic stability of their complexes may still arise from the slight alterations in steric and electronic parameters of these two ligands being unequally sulfonated. Nevertheless, the laws of thermodynamics should be obeyed and equilibria like (4.2) should contribute to the pH-effects in the industrial process, too. 

In a water/chlorobenzene biphasic system, reduction of aromatic aldehydes by hydrogen transfer from aqueous sodium formate catalyzed by [ RuCl2(TPPMS)2 2] provided unsaturated alcohols exclusively (Scheme 10.7). Addition of 3-CD shghtly inhibited the reaction [13]. It was speculated that this inhibition was probably due to complexation of the catalyst by inclusion of one of the non-sulfonated phenyl rings of the TPPMS ligand, however, no evidence was offered. 

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