Hydroformylation with surfactant phosphines

The surfactant phosphines containing poly(ethyleneoxide) 31, sulfonate 47, amine 34 (with R7R2/R3 = H/H/—CH2—N[(CH2)2—NEt2]2, sulfate 36, and phospho-nate 37 moieties were used as tenside ligands to modify Rh catalysts for the hydroformylation of higher alkenes such as 1-hexene, 1-octene, 1-decene, and 1-dode-cene in aqueous/organic two-phase systems [58, 62-65],... 

Efficient biphasic catalysis relies on the rapid mass transfer across the aqueous and organic phases. As indicated, this poses a problem for higher olefins because of their insolubility in water. To tackle the issue and thus to increase the hydroformylation rates, additives, such as co-solvents, surfactants, or modified cyclodextrins, have been explored. A water-miscible organic cosolvent such as an alcohol could increase the solubility of alkenes in the aqueous phase or the catalyst in the organic phase. For example, using [Rh(p-S Bu)(CO)(m-TPPTS)]2 as a catalyst, hydroformylation of 1-octene gave less than 24% conversion after 15 h in water at 80 °C but it reached 90% conversion in 10 h in water/methanol (3 1) [28]. Using Rh-1, 1-dodecene was hydroformylated with 42% conversion to aldehydes in a mixture solvent of water/propanol, while no hydroformylation was observed at all in water alone under identical conditions [29]. The same trend was observed in the reaction of 1-octene catalyzed by Co/BiphTS (BiphTS, trisulfonated tris(biphenyl)phosphine) [30]. 

The phosphinated ligands 135 and 136 prepared from poly(acrylic acid) and from poly(ethyleneimine), respectively, gave active hydroformylation catalysts in reaction with [Rh(acac)(CO)2]. Under the conditions of Table 4.6 low conversions were observed in aqueous/organic biphasic systems, due to the low solubility of 1-octene. Addition of a surfactant (SDS) or an organic co-solvent (MeOH) led to dramatic increases in the yield of aldehydes, revealing the high intrinsic activity of the catalyst [120]. 

Using RuCl(CO)(TPPTS)(BISBIS) the biphasic aqueous hydroformylation of higher olefins in the presence of the cationic surfactant CTAB ensures a TOF > 700 h and regioselectivity >96% for the linear aldehyde Piperazinium cationic surfactants were also successfully applied as catalysis promotion agents in the aq. biphasic hydroformylation of higher olefins. The property of surfactant and ligand can be assumed by the same molecule, e.g. di-sulfonated cetyl(diphenyl)phosphine 42. 1-Dodecene is hydroformylated in water/toluene (3 1) under mild conditions [olefin/Ru = 2500, CO/H2=1, P(CO + H2) = 15 bar, 42/Ru = 10] with TOF = 188 Another approach to... 

The fact that water-soluble sulfonated phosphines may combine the properties of a ligand and a surfactant in the same molecule was first mentioned in 1978 by Wilkinson etal. [11] in their study of the hydroformylation of 1-hexene using rhodium and ruthenium catalysts modified with TPPMS (triphenylphosphine mono-... 

Rhodium complexes modified with the tenside chiral phosphine 5 were used as catalysts in the hydroformylation of styrene, according to Eq. 2, in an aqueous/organic two-phase system [19, 26], The TOFs achieved with the surfactant catalyst Rh/5 were higher (245 h-1) compared with the Rh/TPPTS system (100 Ir1) [26]. The n/iso ratios of the aldehydes were about 0.6 with Rh/TPPTS and ca. 0.4 with the Rh/5 system. Although the phosphine 5 is chiral, virtually no optical activity was observed in the phenylisopropanal product. HQ... 

The sulfonated phosphine system 6 [28-30] was also described as possessing surfactant properties [28], However, 6 and 7 have only been applied in the hydroformylation of 1-tetradecene in methanol followed by biphasic separation of the catalyst after treatment with water [30]. 

Rhodium complexes generated from the polyethylene glycol)-functionalized phosphine 9 (n = 1, x = 0, R = Me, Bu), which should behave as a nonionic surfactant and be able to induce micelle formation, have been used as catalysts in the hydroformylation of 1-dodecene in an aqueous/organic two-phase system [31]. The conversion of 1-dodecene was 80% and the n/iso ratio 60 40, with no carryover of the rhodium catalyst into the organic phase. The Rh/9 (n = 1, x = 0, R = Me, Bu) catalyst remained active after one recycle step [31],... 

The most severe dra wback in homogeneous catalysis is the separation of the catalyst from the reaction mixture. The industrial success of the aqueous two-phase hydroformylation ofpropene to n-butanal [1] in Ruhrchemie AG in 1984 represents the considerable progress in this field. However, aqueous/organic biphasic catalysis has its limitations when the water solubility of the starting materials proves too low, as in hydroformylation of higher olefins (see Chapter 1). To solve this issue, a variety of approaches have been attempted. Additions of co-solvents [2] or surfactants [3, 4] to the system or application of tenside ligands [5, 6] and amphiphilic phosphines [7, 8] are ways to increase the reaction rates. Other approaches such as fluorous biphase system (FBS see Chapter 4) [9], supported aqueous phase catalysis (SAPC see Section 2.6) [10], supercritical CO2 (cf. Chapter 6) [11] and ionic liquids (cf Chapter 5) [12] have also been introduced to deal with this problem. 

The most important large-scale aqueous-organic biphasic process is the hydroformylation of propene into butanal (Scheme 14) catalyzed by [HRh(CO)-(TPPTSlsl, that is the Ruhrchemie-Rhone Poulenc process (63,139,140). The catalyst is dissolved in water, whereas the substrate and product(s) comprise the organic phase. In the heart of this technology is a continuously stirred tank reactor connected to a phase separator. Complete insolubility of the rhodium-phosphine catalyst in the organic phase together with the lack of surfactant behavior of TPPTS assures a full recovery of rhodium by perfect phase separation. The catalytic reaction takes place at 120°C and 5 MPa (CO H2 = 1.01 1)—such conditions are milder than those of the so-called low pressure oxo processes. Propene reacts... 

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