Water soluble sulfonated phosphines

Fell, B. Papadogianakis, G. (1994) Rhodium-catalyzed 2-phase hydroformylation of hex-1-ene with sulfonated tris(4-fluorophenyl)phosphine as water-soluble complex ligands, J. Prakt. Chem. - Chem. Ztg., 336, 591-5. 

Although rhodium recovery is efficient it is difficult to separate it from heavies that are formed in small amounts. Over time these heavies tend to result in some catalyst deactivation. One solution to this problem has been developed by Ruhrchemie/Rhone-Poulenc. In this process sulfonated triphenyl phosphine is used as the ligand, which imparts water solubility to the catalyst. The reaction is two-phase, a lower aqueous phase containing the catalyst and an upper organic phase. Fortunately the catalyst appears to sit at the interface enabling reaction to proceed efficiently. At the end of... 

Water-soluble carbonyls are relatively rare. A route to such a species involves reaction at room temperature of the sulfonated phosphine P(PhS03)33- as its water-soluble Na+ salt with Co2(CO)8 in a two-phase water/toluene mixture, whereupon the product forms in the aqueous phase in high yield.85... 

Considerable work has been conducted on a water-soluble catalyst using sulfonated phosphine-modified rhodium. Details of this chemistry will be described in Chapter 5. The general concept (Figure 2.3) is to make the catalyst water soluble, then after product formation, decant the product. In order for the water-soluble catalyst to be effective, the alkene must dissolve in the aqueous layer. This has been demonstrated on a commercial basis using propene. The low solubility of higher alkenes in the aqueous catalyst layer has proven problematic. The desirable characteristic of the ligand, water solubility, is needed in the separation step but is a disadvantage in the reaction step. 

Selectivity refers to the fraction of raw material alkene that is converted to product aldehyde, but since hydroformylation typically gives both a linear and branched isomer, selectivity also refers to the relative amounts of each. The linear branched (l b) ratio is highly catalyst dependant. One must simultaneously consider whether the proposed catalyst will give the desired l b selectivity and also whether the proposed catalyst is feasible for use with the catalyst/product separation technologies. For example, water extraction of a polar product, such as in the hydroformylation of allyl alcohol to give 4-hydroxybutanal, would not work well with a sodium salt of a sulfonated phosphine since both are water soluble. 

Further variations of the basic motif of 1 comprise carbene le in which the anionic ligands are trifluoroacetate rather than chloride (Fig. 2) [4d]. However, this specific compound shows a significant tendency to isomerize the double bonds of the substrates in addition to its metathetic activity. Moreover, water soluble catalysts have been developed that contain bulky aliphatic phosphine ligands with either a quarternary ammonium group (lf,g) or a sulfonate function (lh) [12]. They have been tested in the ring opening polymerization... 

Water-soluble complexes constitute an important class of rhodium catalysts as they permit hydrogenation using either molecular hydrogen or transfer hydrogenation with formic acid or propan-2-ol. The advantages of these catalysts are that they combine high reactivity and selectivity with an ability to perform the reactions in a biphasic system. This allows the product to be kept separate from the catalyst and allows for an ease of work-up and cost-effective catalyst recycling. The water-soluble Rh-TPPTS catalysts can easily be prepared in situ from the reaction of [RhCl(COD)]2 with the sulfonated phosphine (Fig. 15.4) in water [17]. 

Water-soluble transition-metal complexes have been used recently for transfer hydrogenolysis of halocarbons. Paetzold and Oehme [110] have realized the reductive dehaiogenation of allyl or benzyl halides in the presence of [(phosphine) 2PdCl2] complexes with sulfonated phosphines as ligands (e.g., Ph2P(CH2)3S03K) by... 

In general, the chiral ligands are water-soluble variants of those already studied in purely organic solvents (e.g., the sulfonated chiraphos, A, cyclobutane-diop, C, BDPP, F, MeOBIPHEP-TS, Q, BIFAPS, R and the quaternary ammonium derivatives of diop, D, BDPP, E). Solubility in water could also be achieved by attaching the parent phosphine molecule to a water-soluble polymer (J, M, P). The chiral phosphinites and phosphines derived from carbohydrates (e.g., K and L) have intrinsic solubility in water. During studies of one-phase... 

Figure 4. Water-soluble sulfonated phosphines (continued)...

Hydroxy-phosphines undergo benzoylation with o-sulfobenzoic anhydride in the presence of bases (Na2C03 or BuLi) affording sulfobenzoylated phosphine products. In such a way several mono- and dihydroxy phosphines could be made soluble in water, exemplified by the chiral bisphosphines 53. It should be noted, that this general method allows the preparation of water-soluble sulfonated derivatives of acid-sensitive phosphines, such as DIOP, too, which are not accessible via direct sulfonation [56]. 

The other three studies in the literature also deal with the asymmetric hydroformylation of styrene and all three applied water soluble rhodium -phosphine catalysts (Scheme 4.9). BINAS (44), sulfonated BIPHLOPHOS (43), tetrasulfonated (R,R)-cyclobutane-DIOP (37, m=0) and tetrasulfonated (S,S)-BDPP (36, m=0) were applied as ligands of the rhodium catalyst prepared in situ from [Rh(acac)(CO)2] or [ Rh( Li-OMe)(COD) 2] and the phosphines. The results are summarized in Table 4.4. 

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