Hydroformylation catalysts containing

After Breit and Seiche (67) had reported hydroformylation catalysts containing rhodium and bidentate ligands assembled via hydrogen bonding, Dubrovina and Boerner (68) pointed out that the first use of bidentate ligands obtained via hydrogen bonding in catalysis is represented by the supramolecular work on SPO platinum complexes. 

Other Metal Catalysts. - Hydroformylation catalysts containing Co and Rh have been known for many years and these metals are the only catalysts used industrially. Recently two catalyst systems have been developed that have certain advantages over the conventional catalysts. Pt/Sn chloride complexes show very high selectivity to n-aldehyde. and Reppe-type systems which hydroformylate alkenes in the presence of CO/H2O rather than CO/H2. ... 

Hjortkjaer, J., Scurrell, M.S., and Simonsen, P. (1979) Supported liquid-phase hydroformylation catalysts containing rhodium and triphenylphosphine. J. Mol. Catal., 6 (6), 405 20. 

With Unsaturated Compounds. The reaction of unsaturated organic compounds with carbon monoxide and molecules containing an active hydrogen atom leads to a variety of interesting organic products. The hydroformylation reaction is the most important member of this class of reactions. When the hydroformylation reaction of ethylene takes place in an aqueous medium, diethyl ketone [96-22-0] is obtained as the principal product instead of propionaldehyde [123-38-6] (59). Ethylene, carbon monoxide, and water also yield propionic acid [79-09-4] under mild conditions (448—468 K and 3—7 MPa or 30—70 atm) using cobalt or rhodium catalysts containing bromide or iodide (60,61). 

Hydroformylation of vinyl acetate to give mainly the branched product in >90% ee has been achieved using a rhodium catalyst containing binaphthol and phosphine ligands anchored to polystyrene. 

A method has been developed for the continuous removal and reuse of a homogeneous rhodium hydroformylation catalyst. This is done using solvent mixtures that become miscible at reaction temperature and phase separate at lower temperatures. Such behavior is referred to as thermomorphic, and it can be used separate the expensive rhodium catalysts from the aldehydes before they are distilled. In this process, the reaction mixture phase separates into an organic phase that contains the aldehyde product and an aqueous phase that contains the rhodium catalyst. The organic phase is separated and sent to purification, and the aqueous rhodium catalyst phase is simply recycled. 

In one such procedure a rhodium complex concentrate prepared from a 400 ppm rhodium containing hydroformylation catalyst solution, for which catalytic activity had declined to about 30 percent of its initial value, was concentrated in a wiped-film evaporator to about 27,700 ppm rhodium. This concentrate was oxygenated with tertbu-tylhydroperoxide. After isolation and treatment with triphenylphosphine, a 70% yield of [HRh(CO)(PPh3)3] was obtained.[41]... 

The catalyst containing 2.0% Rh, insoluble in organic solvent, was used for hydroformylation of 1-hexene at 80°C and 43 atm of 1/1 H2/CO. The catalyst concentration was 1 mmole Rh per mole of olefin. After 4 hours a 41% yield of aldehyde was obtained, with a 2.5 1 isomer ratio. Some isomerization to internal olefins also occurred. A significant feature was the rhodium concentration of 2 ppm in the product. 

Thermal decomposition of RhH(CO)(PPh3)3, the well known hydroformylation catalyst, in the absence of H2 and CO leads to a stable cluster shown in Figure 2.36 containing p2-PPh2 fragments [31], Under hydroformylation conditions also other products are found such as benzaldehyde, benzene, and diphenylpropylphosphine. 

The same general principles and the same phosphines (18) can be used for still another variation of catalyst recovery which was demonstrated in the hydroformylation of 1-tetradecene [143], The reaction, catalyzed by the Rh/18 catdyst, was mn in a homogeneous methanolic solution and gave slightly better results than the Rh/PPhs catalyst under identical conditions. After the reaction most of the methanol was distilled off and the remaining solution was extracted with water. The catalyst-containing aqueous phase was evaporated to dryness, the catalyst was taken up in methanol and reused. No loss of activity and selectivity was observed in three recycles. 

The hydrolytic decomposition of a potential fluorophosphite ligand would generate free fluoride ions which would be expected to be detrimental to the activity of a hydroformylation catalyst. The patent literature contains abundant references to the detrimental effects of halogens (6) on hydroformylation catalysts, and based on the patent information, one could not reasonably expect a halophosphite to be a successful hydroformylation ligand. However, a second publication by Klender (7) shows that exposure of / and other fluorophosphites to moisture at temperatures of 250°C to 350°C does not generate fluoride, even at part per million levels. 

A number of reactions, principally of olefinic substrates, that can be catalyzed by supported complexes have been studied. These include hydrogenation, hydrosilylation, hydroformylation, polymerization, oxidative hydrolysis, acetoxylation, and carbonylation. Each of these will be considered in turn together with the possibility of carrying out several reactions consecutively using a catalyst containing more than one kind of metal complex. 

Cyanide-containing cobalt catalysts, particularly potassium pentacyanocobalta-te(II) K3[Co(CN)5], are used in the reduction of activated alkenes (conjugated dienes).26,31 [Co(CO)4]2 is best known as a hydroformylation catalyst, but hydrogenation is also possible under specific conditions. Phosphine-substituted analogs are more successful. 

Thus transition metal complexes capable of effecting cyanation reactions on aromatic nuclei under mild conditions have been discovered Cassar et al. describe such a catalytic system. The past few years have also seen the discovery of asymmetric catalysis. Asymmetric catalysts contain optically active ligands and, like enzymes, can promote catalytic reactions during which substantial levels of optical activity are introduced into the products. This volume contains examples of asymmetric hydrogenation and asymmetric hydroformylation catalysis in the papers, respectively, by Knowles et al. and Pino et al. 

Step 4 Decobaltation of the Reaction Product. The product of the hydroformylation reactor containing the catalyst as a mixture of cobalt carbonyl hydride and dicobalt octacarbonyl is fed to the decobaiting section. Mixing the product at 120 °C and 10 atm with a dilute formic acid/ cobalt formate solution in the presence of air decomposes the catalyst (Reaction 9) (12). 

The complex [Rh(nbd)(amphos)2]3+, which contains the water-soluble ligand amphos (33), has been prepared. In a two-phase system this complex acted as a hydroformylation catalyst for 1-hexene.133 Isomerization of the alkene occurred to a limited extent. In the presence of H2 and CO the dicarbonyl [Rh(CO)2(amphos)2]3+ was thought to be formed. 

All Group VIII, IX and X transition metals show some catalytic activity for hydroformylation, although cobalt and rhodium are the most active, rhodium catalysts being 104 times more reactive. More recently, platinum catalysts containing the trichlorostannate ligand have been shown to be selective catalysts that effect hydroformylation under mild conditions.6... 

The hydroformylation of ally and vinyl acetals yields some useful intermediates. Allyl acetate undergoes partial double bond migration prior to hydroformylation with a cobalt catalyst in the absence of phosphine (equation 20).2-5 Rhodium catalysts containing chelating phosphines are more selective to the linear aldehyde.31... 

Some of the highest enantiomeric excesses in hydroformylation reactions of styrene (-70-80% ee) have been obtained with a platinum catalyst containing the chiral ligand (2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]pyrrolidine (17 (-)-BPPM).39... 

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