Ligands monosulfonated triphenylphosphine

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. 

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. 

It occurred to us that ionic interactions might be a highly suitable binding motif to enforce the formation of heterobidentate ligand combinations [48[. The assembly ligand 14 /IS has been formed from the well-known TPPMS (14, monosulfonated triphenylphosphine sodium salt) and 3-(diphcnylphosphinyl)aniline hydrochloride (IS) by a simple ion-exchange reaction (Scheme 10.6). The coordination behavior ofthe ion-pair 14 /I S has been tested with various transition metal complexes. Other... 

The use of triphenylphosphine as ligand led to acceptable rates in ILs, but with high rhodium leaching into the organic phase. Recourse to sulfonated phosphines such as monosulfonated triphenylphosphine retained the catalyst in the ionic liquid phase but decreased its activity significantly. This drawback was surmounted by the use of 47 (Table 1.5), which was derived from a simple cation metathesis reaction between TPPTS (37) and 1-butyl-2,3-dimethylimi-dazolium chloride [bdmim][Cl] in acetonitrile. 

Sulfonated triphenylphosphine [TPPTS (triphenylphosphine, m-trisulfonated) tri(m-sulfophenyl)phosphine] (II-l) and monosulfonated triphenylphosphine [TP-PMS (triphenylphosphine, monosulfonated) 3-(diphenylphosphino)benzenesul-fonic acid] (II-2) are commercially available ligands and their sodium salts are water-soluble [15]. The Na salt of the ligand TPPTS is very soluble and may be too soluble in water, hence moderately soluble TPPMS is preferred. Another water-soluble phosphine is 2-(diphenylphosphinoethyl)trimethyl ammonium halide (II-11) [16]. A number of other water-soluble phosphines are now known (Table 1.2). Pd complexes, coordinated by these phosphines, are soluble in water, and Pd-catalyzed reactions can be carried out in water, which is said to have an accelerating effect in some catalytic reactions. 

Another approach to increase solution stability and decrease the number of isomers in [99mTc]HYNIC complexes involves the use of a water-soluble phosphine (Fig. 2 TPPTS, disodium triphenylphosphine-3,3 -disulfonate, TPPDS, and sodium triphenylphosphine-3-monosulfonate, TPPMS) as a second coligand [42]. It was found that the combination of XV120 with tricine and a phosphine coligand results in a versatile ternary ligand system that forms 99mTc... 

The general flow scheme for this alternative is shown in Figure 15. After the homogeneous reaction, catalyzed for instance by a rhodium catalyst containing triphenylphosphine monosulfonic acid as complex ligand, the solubilizer methanol is distilled off. The catalyst system now becomes insoluble and is separated by extraction with water in the third unit. The products C and D, in this case the aldehydes, can be separated as the second liquid phase. After evaporation of the aqueous catalyst solution to dryness (unit 4) the catalyst is dissolved in the solvent methanol for a new reaction step (unit 5). 

Researchers at INTEVEP SA (Ven) have recently shown that the regioselective hydrogenation of benzo[fo]thiophene (BT) to dihydrobenzo[fo]thiophene (DHBT) (Eq. 2) can be performed in a 1 1 water/decalin mixture using an in situ catalyst system formed by addition of an excess of either m-monosulfonated triphenylphos-phine (TPPMS) or trisulfonated triphenylphosphine (TPPTS) to various Ru(II) precursors [2 a], It is believed that the catalytically active species is a mononuclear Ru(II) complex with chloride and hydride ligands. 

The details and the backgroimd of RCH/RP s developments have been described elsewhere. The work of Kuntz (then at RP see Section 2.4.1.1.1) on trisulfonated triphenylphosphine (TPPTS) and the industrial implementation and improvements developed by Ruhrchemie eventually laid the foundation for the subsequent successful commercialization [3]. TPPTS is the ideal ligand modifier for the oxo-active HRh(CO)4. Without any expensive preformation steps, three of the four CO ligands can be substituted by the readily soluble (1100 g L water) and nontoxic (LD50, oral > 5000 mg kg ) TPPTS, which yields the hydrophilic 0x0 catalyst HRh(CO)[P(3-sulfophenyl-Na)3]3. The trisulfonation, in particular, permits the fine adjustment ofTPPTS and thus of the hydrophilic versus the hydrophobic properties hydrophilicity is ranked in the order TPP3 S > TPPDS > TPPMS, from the trisulfonated through to the monosulfonated species. 

Figure 15.1 Typical hydroformylation monophosphine ligands TPPTS (3, triphenylphos-phine trisulfonate, sodium salt), TPPTIM (4, triphenylphosphine trisulfonate, l-butyl-2,3-dimethylimidazolium salt), and TPPMS (5, triphenylphosphine monosulfonate, sodium salt).

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