Sulfonated phosphine ligands hydroformylation

When water-miscible ionic liquids are used as solvents, and when the products are partly or totally soluble in these ionic liquids, the addition of polar solvents, such as water, in a separation step after the reaction can make the ionic liquid more hydrophilic and facilitate the separation of the products from the ionic liquid/water mixture (Table 5.3-2, case e). This concept has been developed by Union Carbide for the hydroformylation of higher alkenes catalyzed by Rh-sulfonated phosphine ligand in the N-methylpyrrolidone (NMP)/water system. Thanks to the presence of NMP, the reaction is performed in one homogeneous phase. After the reaction. 

The synthesis of aldehydes via hydroformylation of alkenes is an important industrial process used to produce in the region of 6 million tonnes a year of aldehydes. These compounds are used as intermediates in the manufacture of plasticizers, soaps, detergents and pharmaceutical products [7], While the majority of aldehydes prepared from alkene hydroformylation are done so in organic solvents, some research in 1975 showed that rhodium complexes with sulfonated phosphine ligands immobilized in water were able to hydroformylate propene with virtually complete retention of rhodium in the aqueous phase [8], Since catalyst loss is a major problem in the production of bulk chemicals of this nature, the process was scaled up, culminating in the Ruhrchemie-Rhone-Poulenc process for hydroformylation of propene, initially on a 120000 tonne per year scale [9], The development of this biphasic process represents one of the major transitions since the discovery of the hydroformylation reaction. The key transitions in this field include [10] ... 

Stelzer and co-workers reported a number of chiral water-soluble secondary phosphines [14], prepared by nucleophilic phosphination of primary phosphines with fluorinated aryl sulfonates in the superbasic medium DMSO/KOH. Further reaction with alkyl halides gives bidentate tertiary phosphines with P-chirality, but only racemic versions have been reported so far. Hanson et al. introduced so-called surface-active phosphines into asymmetric aqueous-phase catalysis. One of the main problems inherent to two-phase catalysis is the often very low miscibility of the substrates in the aqueous phase. Insertion of long alkyl chains between phosphorus atoms and phenyl groups in sulfonated phosphine ligands has been proven to increase reaction rates in the Rh-catalyzed hydroformylation of 1-octene [15], This concept was extended to a number of chiral ligands, i.e., the monoden-... 

An aqueous two-phase hydroformylation went on stream at Ruhrchemie AG in 1984 (fourth generation) at their site in Oberhausen/Germany with an annual capacity of 100 kt/a [1]. The current capacity is 500kt/a. The Rh catalyst is immobilized in the aqueous phase. A sulfonated phosphine ligand (TPPTS, trisodium salt of 3,3, 3 Lphosphinidynetris(benzenesulfonic acid) confers the metal catalyst with high solubility in water. The catalyst is removed into the aqueous phase before distillation of the product, which avoids thermal stress. The loss of rhodium is in the range of parts per billion. 

As Monflier and coworkers [48] have shown, the rhodium-catalyzed hydroformylation of triglycerides in water pressure can be supported by the addition of randomly methylated P-cyclodextrines (RAME-P-CDs). Syngas pressure (20-80 bar), temperature (50-80 °C), nature of the sulfonated phosphine ligand, and the amount of R AME-P-CD had a profound influence of the catalytic results. 

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. 

Indeed, sulfonated phosphine ligands appear to have been first developed and studied for industrial application in hydroformylation. An early example of hydroformylation in a two-phase system (1-hexene-water) with the TPPMS analogue of the Wilkinson complex appeared in the public-domain literature in the 1970s [126]. 

The latest development in industrial alkene hydroformylation is the introduction by Rurhchemie of water-soluble sulfonated triphenylphosphine ligands.94 Hydroformylation is carried out in an aqueous biphasic system in the presence of Rh(I) and the trisodium salt of tris(m-sulfophenyl)phosphine (TPPTN). High butyraldehyde selectivity (95%) and simple product separation make this process more economical than previous technologies. 

A number of chiral bisphosphines related to DiPAMP(l) were prepared and evaluated in asymmetric catalysis. Many variants were closely equivalent but none were superior to the parent compound. In addition, some monophosphines containing sulfone substituents were quite effective. These had the particular advantage of being usable in water solution. Several new DIOP derivatives were tried in the hydroformylation of vinyl acetate but only modest enantiomeric excesses were achieved. A 72% enantiomeric excess was achieved on dehydrovaline under relatively forcing conditions using DiCAMP(3). This result was remarkable since these phosphine ligands generally work very poorly, if at all, on tetrasubstituted olefins. 

Water soluble ligands greatly facilitate catalyst separation. Examples are (22-XLI)174 and (22-XLII),175 which are used in hydroformylations and hydrogenation catalysis, respectively. Rhodium complexes of the sulfonated phosphine (22-XLI) are used in the production of butyraldehyde, a large-scale process developed by Ruhrchemie/Rhone-Poulenc.174... 

First of all, these properties were used to separate the sulfonated phosphine from the excess of sulfuric acid affer sulfonation by forming a triisooctylammo-nium salt in toluene, which is totally insoluble in water [1], Later it was discovered, that the re-immobilized ligand in toluene as well as the immobilized ligand in water are useful and remarkably stable catalyst systems. As classical homogeneous catalysts they are very active, e. g., for the hydroformylation of higher olefins and olefins with internal double bonds. 

Researchers have worked to alleviate the problems of separation and corrosion in processes such as the oxo process by designing catalysts that are confined in a separate phase from the reactants (see Section 14.2.4). A commercially successful approach for propene hydroformylation resulted from preparation of water-soluble rhodium complex catalysts by sulfonation of the phenyl rings of the triphenyl phosphine ligands. The catalyst is used in a reactor with two liquid phases the propene is concentrated in the organic phase and the catalyst in the aqueous phase near the interface. The CO -I- H2 is bubbled into a mixed reactor, and the two-phase liquid product flows to a settler the organic product flows to downstream separation devices, and the aqueous phase with the catalyst is recycled to the reactor. 

The surface-active character of sulfonated phosphines, e.g., TPPMS (lb, n = 2), was already noted in 1977 by Wilkinson et al., who also commented on the participation of the SOy groups in the coordination of these ligands to transition metals in catalyst complexes (13) [50]. Rh complexes of lb (TPPDS) have been employed as catalysts in hydroformylation of olefins in biphasic media [21a]. The p-isomer 2b (Ph2P—C6H4-p-S03K) was, however, much more reactive in the presence of a surfactant (lauric acid) [21b]. Rh catalysts using TPPMS have been employed in... 

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-... 

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