Cobalt carbonyls reactions

A number of simple and inexpensive materials catalytically promote the cobalt-carbonylation (Reaction 2) in aqueous solution. These include ion-exchange resins, zeolites, or special types of activated carbon. Formation of the active catalyst in a separate reactor is thus economically feasible. The mechanism of this catalysis has not yet been elucidated and seems to differ for each promoter mentioned. After an induction period during which the cobalt fed to the reactor is partially retained by the promoter, fully active materials have absorbed cobalt carbonyl anion Co(CO)4 (ion exchange resins), Co2+ cation (zeolites), or a mixture of Co2+, cobalt carbonyl hydride, and cluster-type cobalt carbonyls (activated carbon). This can be shown by analytical studies (extraction, titration, and IR studies) of active material withdrawn from the reactor. 

CatalystY of cobalt-carbonyl reactions can ntiUze tbe water solnbiUty of the salt and the hydrocarbon solnbihty of the metal metal dimer. Ion pairing is important in the disproportionated metal complexes, and traces of water in organic solvents can not only serve as catalysts for this reaction but can also influence the equilibrium position by stabilizing the ionic products. 

Other reactions are alkane formation by hydrogenation, ketone formation (especially with ethylene ), ester formation through hydrogen transfer and formate ester synthesis. An improved catalyst system in which one CO ligand of CoH(CO)4 is substituted with a trialkylphosphine ligand , was disclosed by Shell workers in the early 1960s. With this catalyst, which is more thermally stable than the unsubstituted cobalt carbonyl, reaction proceeds at 140-190 C with 3-7 MPa of CO and Hj. Additionally, mostly linear aldehydes are obtained from linear terminal and internal olefins. This remarkable result arises from the high preference for the terminal addition to an a-olefin, and the isomerization of the olefinic position which occurs simultaneously with hydroformyiation. 

The carbonylation of a benzyl halide in the presence of iron pentacarbonyl to give a phenylacetic acid may serve to exemplify the interaction of a metal carbonyl, carbon monoxide, PT catalyst, aqueous sodium hydroxide, and the substrate [79]. Fe(CO)5 is attacked by QOH at the interphase, and the species formed is extracted into the depths of the oganic phase, where it reacts with CO and benzyl halide (Eqs. 13 and 14). This new anion 3 is the actual catalyst. It reacts with a second benzyl halide to give a non-ionic intermediate 4 (Eq. 15). By insertion of CO and attack of QOH, 4 is decomposed to the reaction product under regeneration of 3 (Eq. 16). Thus, the action of the PT catalyst is twofold. Firstly it transports the metal carbonyl anion. More important seems to be its involvement in the (rate-determining) decomposition step. A basically similar mechanism was proposed for cobalt carbonyl reactions [80], which have been modified somewhat quite recently (see below). 

Carbonylation and decarbonylation reactions of alkyl complexes in catalytic cycles have been reviewed . A full account of the carbonylation and homologation of formic and other carboxylic acid esters catalysed by Ru/CO/I systems at 200 C and 150-200 atm CO/H2 has appeared. In a novel reaction, cyclobutanones are converted to disiloxycyclopentenes with hydrosilane and CO in the presence of cobalt carbonyl (reaction 4) . The oxidative addition of Mel to [Rh(CO)2l2] in aprotic solvents (MeOH, CHCI3, THF, MeOAc), the rate determining step in carbonylation of methyl acetate and methyl halides, is promoted by iodides, such as Bu jN+I", and bases (eg 1-methylimidazole) . A further kinetic study of rhodium catalysed methanol carbonylation has appeared . The carbonylation of methanol by catalysts prepared by deposition of Rh complexes on silica alumina or zeolites is comparable with the homogeneous analogue . 

Carbonyiation of butadiene gives two different products depending on the catalytic species. When PdCl is used in ethanol, ethyl 3-pentenoate (91) is obtained[87,88]. Further carbonyiation of 3-pentenoate catalyzed by cobalt carbonyl affords adipate 92[89], 3-Pentenoate is also obtained in the presence of acid. On the other hand, with catalysis by Pd(OAc)2 and Ph3P, methyl 3,8-nonadienoate (93) is obtained by dimerization-carbonylation[90,91]. The presence of chloride ion firmly attached to Pd makes the difference. The reaction is slow, and higher catalytic activity was observed by using Pd(OAc) , (/-Pr) ,P, and maleic anhydride[92]. Carbonyiation of isoprcne with either PdCi or Pd(OAc)2 and Ph,P gives only the 4-methyl-3-pentenoate 94[93]. 

Ma.nufa.cture. Nickel carbonyl can be prepared by the direct combination of carbon monoxide and metallic nickel (77). The presence of sulfur, the surface area, and the surface activity of the nickel affect the formation of nickel carbonyl (78). The thermodynamics of formation and reaction are documented (79). Two commercial processes are used for large-scale production (80). An atmospheric method, whereby carbon monoxide is passed over nickel sulfide and freshly reduced nickel metal, is used in the United Kingdom to produce pure nickel carbonyl (81). The second method, used in Canada, involves high pressure CO in the formation of iron and nickel carbonyls the two are separated by distillation (81). Very high pressure CO is required for the formation of cobalt carbonyl and a method has been described where the mixed carbonyls are scmbbed with ammonia or an amine and the cobalt is extracted as the ammine carbonyl (82). A discontinued commercial process in the United States involved the reaction of carbon monoxide with nickel sulfate solution. 

In the reaction of aHyl alcohol with carbon monoxide using cobalt carbonyl, Co(CO)g as the catalyst, in the presence of a small amount of hydrogen and carbon monoxide under pressure, 9.8 MPa (1420 psi), at 100°C, intramolecular hydroesterification takes place, yielding y-butyrolactone [96-48-0] (16). 

The first CO route to make adipic acid is a BASF process employing CO and methanol in a two-step process producing dimethyl adipate [627-93-0] which is then hydroly2ed to the acid (43—46). Cobalt carbonyl catalysts such as Co2(CO)g are used. Palladium catalysts can be used to effect the same reactions at lower pressures (47—49). 

C-19 dicarboxyhc acid can be made from oleic acid or derivatives and carbon monoxide by hydroformylation, hydrocarboxylation, or carbonylation. In hydroformylation, ie, the Oxo reaction or Roelen reaction, the catalyst is usually cobalt carbonyl or a rhodium complex (see Oxo process). When using a cobalt catalyst a mixture of isomeric C-19 compounds results due to isomerization of the double bond prior to carbon monoxide addition (80). 

In hydrocarboxylation, the Reppe reaction, the catalyst can be nickel or cobalt carbonyl or a palladium complex where R = H or alkyl. 

A simplified reaction scheme is shown in Fig. 26.5 Again, the ability of rhodium to change its coordination number and oxidation state is crucial, and this catalyst has the great advantage over the conventional cobalt carbonyl catalyst that it operates efficiently at much lower temperatures and pressures and produces straight-chain as opposed to branched-chain products. 

Cobalt carbonyl radicals and radical reactions of cobalt carbonyl. G. Palyi, F. Ungvary, V. Galamb andL. Marko, Coord. Chem. Rev., 1984, 53, 37-53 (90). 

The formation of isomeric aldehydes is caused by cobalt organic intermediates, which are formed by the reaction of the olefin with the cobalt carbonyl catalyst. These cobalt organic compounds isomerize rapidly into a mixture of isomer position cobalt organic compounds. The primary cobalt organic compound, carrying a terminal fixed metal atom, is thermodynamically more stable than the isomeric internal secondary cobalt organic compounds. Due to the less steric hindrance of the terminal isomers their further reaction in the catalytic cycle is favored. Therefore in the hydroformylation of an olefin the unbranched aldehyde is the main reaction product, independent of the position of the double bond in the olefinic educt ( contrathermodynamic olefin isomerization) [49]. 

Cobalt carbonyl complexes with tertiary phosphine ligands are not volatile. This makes possible a distillative separation of the reaction products from the cobalt catalyst system (Fig. 5). 

If cobalt carbonylpyridine catalyst systems are used, the formation of unbranched carboxylic acids is strongly favored not only by reaction of a-olefins but also by reaction of olefins with internal double bonds ( contrathermo-dynamic double-bond isomerization) [59]. The cobalt carbonylpyridine catalyst of the hydrocarboxylation reaction resembles the cobalt carbonyl-terf-phos-phine catalysts of the hydroformylation reaction. The reactivity of the cobalt-pyridine system in the hydrocarboxylation reaction is remarkable higher than the cobalt-phosphine system in the hydroformylation reaction, especially in the case of olefins with internal double bonds. This reaction had not found an industrial application until now. 

Organomercury compounds undergo a similar reaction. Alkyl and aryl Grignard reagents can be converted to carboxylic esters with Fe(CO)5 instead of CO. Amides have been prepared by the treatment of trialkyl or triarylboranes with CO and an imine, in the presence of catalytic amounts of cobalt carbonyl ... 

Treatment of the 1,2-oxazines 52 with carbon monoxide at 1000 psi in the presence of cobalt carbonyl brings about insertion of carbon monoxide to form the 1,3-oxazepines S3 <96TL2713>. A convenient route to P-lactams fused to oxepines is made available by alkene metathesis. Thus reaction of 4-acetoxyazetidin-2-one with ally alcohol in the presence of zinc acetate, followed by iV-allylation of the nitrogen affords the derivative 54 which cyclises by RCM to form the oxazepinone 55 <96CC2231>. The same communication describes a similar synthesis of 1,3-dioxepines. 

Only a few other cobalt complexes of the type covered in this review (and therefore excluding, for example, the cobalt carbonyls) have been reported to act as catalysts for homogeneous hydrogenation. The complex Co(DMG)2 will catalyze the hydrogenation of benzil (PhCOCOPh) to benzoin (PhCHOHCOPh). When this reaction is carried out in the presence of quinine, the product shows optical activity. The degree of optical purity varies with the nature of the solvent and reaches a maximum of 61.5% in benzene. It was concluded that asymmetric synthesis occurred via the formation of an organocobalt complex in which quinine was coordinated in the trans position (133). Both Co(DMG)2 and cobalamin-cobalt(II) in methanol will catalyze the following reductive methylations ... 

The Co2(CO)g/pyridine system can catalyze carbomethoxylation of butadiene to methyl 3-pentenoate (Eq. 6.44) [80]. The reaction mechanism of the cobalt-catalyzed carbalkoxylation of olefins was investigated and the formation of a methoxycar-bonylcobalt species, MeOC(0)Co from a cobalt carbonyl complex with methanol as an intermediate is claimed [81, 82]. 

The reaction of dicobalt octacarbonyl with [NP(OPh) (OCgH P-Pl O 3)n gives three different phosphine bound cobalt carbonyls. The initial hydroformylation activity of the heterogeneous catalyst... 

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. 

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