Cobalt carbonyls as catalysts

The first stage of the process is a hydroformylation (oxo) reaction from which the main product is n-butyraldehyde. The feeds to this reactor are synthesis gas (CO/H2 mixture) and propylene in the molar ratio 2 1, and the recycled products of isobutyraldehyde cracking. The reactor operates at 130°C and 350 bar, using cobalt carbonyl as catalyst in solution. The main reaction products are n- and isobutyraldehyde in the ratio of 4 1, the former being the required product for subsequent conversion to 2-ethylhexanol. In addition, 3 per cent of the propylene feed is converted to propane whilst some does not react. 

The Schiff bases from substituted benzaldehydes and anilines will carbonylate in the presence of cobalt carbonyl, as catalyst at 225°C. producing phthalimidine derivatives, XVI, in good yield (70, 52). This reaction may be explained as an... 

The low-pressure oxo process based on rhodium complex catalysts has largely replaced the older, high-pressure process, which used cobalt carbonyls as catalyst. The low-pressure process is operated at about 100°C and 200psig. A new generation oxo process with bisphosphite modified rhodium catalyst is shown schematically in Fig. 10.5. 

In summary, further study of the application of the oxo reaction to the 2,3-anhydro sugars, using cobalt carbonyls as catalysts, appears to oflFer little promise. It is possible that use of a more-active carbonyl-insertion catalyst, for example, that of rhodium, might be worth while. 

The addition of HCN to olefins catalyzed by complexes of transition metals has been studied since about 1950. The first hydrocyanation by a homogeneous catalyst was reported by Arthur with cobalt carbonyl as catalyst. These reactions gave the branched nitrile as the predominant product. Nickel complexes of phosphites are more active catalysts for hydrocyanation, and these catalysts give the anti-Markovnikov product with terminal alkenes. The first nickel-catalyzed hydrocyanations were disclosed by Drinkard and by Brown and Rick. The development of this nickel-catalyzed chemistry into the commercially important addition to butadiene (Equation 16.3) was conducted at DuPont. Taylor and Swift referred to hydrocyanation of butadiene, and Drinkard exploited this chemistry for the synthesis of adiponitrile. The mechanism of ftiis process was pursued in depth by Tolman. As a result of this work, butadiene hydrocyanation was commercialized in 1971. The development of hydrocyanation is one of tfie early success stories in homogeneous catalysis. Significant improvements in catalysts have been made since that time, and many reviews have now been written on this subject. ... 

The introduction of alkyl phosphine complexes of cobalt carbonyl as hydroformylation catalysts was reported to have a significant effect on product composition (50, 51). Slaugh and Mullineaux (52) reported that hexanol with a 91% linear distribution was formed by the hydroformylation of 1-pentene at 150°C, 500 psi, H2/CO 2.0, catalyst [Co2(CO)8 + 2(n-C4H9)3P]. Under the same conditions except at a temperature of 190°C, the n-hexanol was 84% of the hexyl alcohol produced. 

The spacer units in 3.60 are assembled from polyphosphazenes that bear p-bromophc-noxy side groups via a lithiation reaction, and treatment with a diorganochlorophosphine to give 3.62. The chemistry is summarized in reaction sequence (45).107 Polymer 3.62 coordinates to a variety of metallo species,108 including osmium cluster compounds and cobalt carbonyl hydroformylation catalysts. When used as a polymeric hydroformylation catalyst, this latter species proved how stable the polyphosphazene backbone is under the drastic conditions often needed for these types of reactions. The weakest bonds in the molecule proved to be those between the phosphine phosphorus atoms and the aromatic spacer groups. 

The carbonylation of methanol to acetic acid and methyl acetate, and the carbonylation of the latter to acetic anhydride, was found by W. Reppe at BASF in the 1940s, using iodide-promoted cobalt salts as catalyst precursors. This process required very high pressure (600 bar) as well as high temperatures (230°C) and gave ca. 90% selectivity for acetic acid. 

Substituted cobalt carbonyls of the type Co2(CO)6L2 have also been compared to binary cobalt carbonyls as hydroformylation catalysts for linear aldehydes. One study compared four Co2(CO)6L2 complexes (L = tertiary phosphines with functionahzed alkyl groups) to the well-known complexes Co2(CO)6(P n-Bu 3)2 and Co2(CO)g. The bulky phosphine substituent P(CH2CH2CH20CH2CH2)3 showed lower activity than the others, but analogous selectivity. 

Hydro(methoxycarbonyl)ation of epoxides has also been achieved this was accomplished by allowing the substrate to react with carbon monoxide and methanol at elevated pressures, at temperatures above 130, in the presence of cobalt salts or cobalt carbonyl as the catalyst. ... 

Carbonylation of Alkyl Halides, Using Carbon Monoxide and Alkali-metal Cobalt Tetracarbonyl as Catalyst... 

Again using PEGs as PT catalysts, the Alper group reinvestigated the carbonylation of benzyl halides in the presence of Co2(CO)8. They were able to characterize and investigate -benzyl, 3-benzyl, and ( -phenylacetyl) cobalt carbonyls as intermediates, and arrived at an elaborate mechanistic cycle [84],... 

The reaction as originally used employed cobalt compounds as catalysts at temperatures of ca. 150° and > 300 psi pressure, and some three million tons a year of alcohols, usually C7-C9, are produced in this way. The process ordinarily gives both straight- and branched-chain products in the ratio ca. 3 1, but considerable efforts have been made to improve the yield of the linear product patents describe the use of tributylphosphine-substituted cobalt carbonyls for this purpose.60... 

CO in a mixed solvent of H2O/DMF (1/1 or 1/2, v/v), and even in water alone, depending on the solubility of the substrate (Eq. 6.31)7 The palladium(II) complexes Pd(OAc)2, K2PdCl4, PdCl2(PPh3)2, and Pd(NH3)4Cl2 are used as the precursors of the catalyst, using either K2CO3 or NaOAc as the base. lodoxyarenes can be carbonylated in water alone due to their solubility in the solvent. Recent work has been done on the use of water-soluble catalysts. Under the appropriate pressure and temperature conditions, aryl mercaptans (thiophenols) can also be carbonylated in aqueous media with cobalt carbonyl as the catalyst. " ... 

Phase-transfer catalysis has been found to be a useful tool for promoting carbonylation reactions under mild conditions [31]. Examples of this are the cyanonickel(ll) complex phase-transfer catalyzed carbonylation of allyl halides to acids [32], and the conversion of benzylic halides and methyl iodide to acids using cobalt carbonyl as the catalyst [33]. 

Under mild conditions (1-4 bar CO, 25-60 °C), high yields of the desired produets were produced. Benzyl, allyl, aryl, and vinyl halides containing primary, secondary, or tertiary aleohol groups were readily converted to a variety of lactones, including phthalides and butenolides (Scheme 2.160a). Sinee then, 2-bromo benzyl aleohol has been tested as a substrate in various systems, such as carbonylation with a flow microreactor,[ C]-labelled compounds, and microwave-promoted with Mo(CO)g as a carbon monoxide source (Scheme 2.160b). Cobalt carbonyl as a cheaper catalyst was also applied in the intramolecular cyclization of aryl halides (Scheme 2.160c). ... 

The use of the cobalt triad carbonyls as catalysts continues to provide many papers for this report. Publications cover the silylformylation of 1-Hexyne catalyzed by diodium-cobalt carbonyl clusters the formation of hydroxycarbene cobalt carbonyl derivatives, the use of rhodium cluster carbonyls in the water-gas shift reaction Rh4(CO) 2> and Co3Rh(CO)] 2 catalysts for the hydrosilation of isoprene, cyclohexanone and cyclohexenone catalytic reduction of NO by CO and the carbonylation of unsaturated compounds The chemistry of iridium carbonyl cluster complexes has been extended by making use of capping reactions with HgCl2and Au(PPh3)Q... 

The acetic acid process was developed at BASF in Ludwigshafen to plant-scale application [543, 1007, 1008, 1012]. It operates with cobalt/ iodine as catalyst and with addition of water at about 250 °C and 750 atm in the carbonylation reactor [1012]. The greatest difficulty in the development was presented by the corrosiveness of the reaction mixture because special steels as well as platinum, titanium and tantalum linings corrode. The problem was solved by the use of Hastelloy C (Ni, Mo, Cr) [585,1007, 1008, 1012] and the somewhat less stable Hastelloy B (Ni, Mo, Cr) [585]. 

The temperature-pressure behavior, as well as the solvent dependence of the equilibrium species of phosphine-substituted and unsubstituted cobalt carbonyl oxo catalysts, was investigated using in situ NMR techniques (59). The solvent polarity was found to have a dramatic effect on the equilibrium concentrations of species present and a new, as yet unidentified species was observed to be present preferentially in nonpolar solvents. 

Cobalt, Rhodium and Iridium. - This group is justifiably recognised for its catalytic prowess and a number of papers each year are targeted at using Co, Rh or Ir carbonyls as catalysts for some reaction or other. Often, papers deal with the simple carbonyls themselves, such as that by Kurhinen and Pakkanen examining the temperature-programmed decomposition, oxidation, and reduc-... 

Cobalt has an odd number of electrons, and does not form a simple carbonyl in oxidation state 0. However, carbonyls of formulae Co2(CO)g, Co4(CO)i2 and CoJCO),6 are known reduction of these by an alkali metal dissolved in liquid ammonia (p. 126) gives the ion [Co(CO)4] ". Both Co2(CO)g and [Co(CO)4]" are important as catalysts for organic syntheses. In the so-called oxo reaction, where an alkene reacts with carbon monoxide and hydrogen, under pressure, to give an aldehyde, dicobalt octacarbonyl is used as catalyst ... 

An early attempt to hydroformylate butenediol using a cobalt carbonyl catalyst gave tetrahydro-2-furanmethanol (95), presumably by aHybc rearrangement to 3-butene-l,2-diol before hydroformylation. Later, hydroformylation of butenediol diacetate with a rhodium complex as catalyst gave the acetate of 3-formyl-3-buten-l-ol (96). Hydrogenation in such a system gave 2-methyl-1,4-butanediol (97). 

Rhodium Ca.ta.lysts. Rhodium carbonyl catalysts for olefin hydroformylation are more active than cobalt carbonyls and can be appHed at lower temperatures and pressures (14). Rhodium hydrocarbonyl [75506-18-2] HRh(CO)4, results in lower -butyraldehyde [123-72-8] to isobutyraldehyde [78-84-2] ratios from propylene [115-07-17, C H, than does cobalt hydrocarbonyl, ie, 50/50 vs 80/20. Ligand-modified rhodium catalysts, HRh(CO)2L2 or HRh(CO)L2, afford /iso-ratios as high as 92/8 the ligand is generally a tertiary phosphine. The rhodium catalyst process was developed joindy by Union Carbide Chemicals, Johnson-Matthey, and Davy Powergas and has been Hcensed to several companies. It is particulady suited to propylene conversion to -butyraldehyde for 2-ethylhexanol production in that by-product isobutyraldehyde is minimized. 

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