Cobalt carbonyl-hydrocarbonyl

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. 

An unusual synthesis of acyldienes from conjugated dienes, carbon monoxide, and alkyl or acyl halides using cobalt carbonylate anion as a catalyst should be mentioned here (57). The reaction apparently involves the addition of an acylcobalt carbonyl to a conjugated diene to produce a l-acylmethyl-7r-allylcobalt tricarbonyl, followed by elimination of cobalt hydrocarbonyl in the presence of base. The reaction can thus be made catalytic. Since the reaction was discussed in detail in the recent review by Heck (59), it will not be pursued further here. 

It has been observed that rapid isomerization accompanies the cobalt carbonyl-catalyzed hydrosilation of olefins (18). The reaction of equimolar amounts of a trisubstituted silane and dicobalt octacarbonyl has been shown to result in the formation of cobalt hydrocarbonyl (cf. Section IV). A very effective isomerization catalyst may be prepared by treatment of a solution of Co2(CO)8 in olefin ( 0.01 M) with a silicon hydride in sufficient quantity to slightly exceed the cobalt carbonyl concentration. 

Heck demonstrated Eq. (89) for a number of acylcobalt carbonyls, preparing them from the corresponding alkyl halide and sodium cobalt carbonylate. In the presence of bases, cobalt hydrocarbonyl regenerated cobalt carbonylate ion and a catalytic reaction resulted at atmospheric pressure and at temperatures from 0° to 100° C. Thus the following reaction was reported in 56% yield at 50° C ... 

The last step represents an intramolecular nucleophilic lysis of the acyl-cobalt carbonyl, with the regeneration of cobalt hydrocarbonyl. Similar... 

The unique hydrogenating ability of a mixture of synthesis gas and a cobalt catalyst is intimately associated with the chemistry of the cobalt compounds formed under these conditions, namely dicobalt octacarbonyl and cobalt hydrocarbonyl. Before any mechanism for the hydrogenation reaction is discussed it is imperative to consider, if even briefly, the chemistry of the cobalt carbonyls. 

In spite of its instability in the liquid state, cobalt hydrocarbonyl can be carried from one vessel to another as a vapor highly diluted with carbon monoxide or any other inert gas at room temperature and pressure. A semiquantitative study of the rate of decomposition in both the vapor state and in hexane solution indicates that the half-life is dependent on the initial concentration (Sternberg, Wender, Friedel, and Orchin, 29). It can be absorbed in water at 0° and behaves as a strong mineral acid. The ionization provides a cobalt carbonyl anion ... 

Cobalt hydrocarbonyl can be made by solution methods and by high-pressure synthesis. The solution method involves the formation of a salt of cobalt carbonyl such as K[Co(CO)4] and its careful acidification to give the hydrocarbonyl (Gilmont and Blanchard, 43). The alkali salt is made by absorption of carbon monoxide in an alkaline cobalt(II) cyanide suspension according to the equation ... 

Acidification of the potassium cobalt carbonyl with hydrochloric acid in a stream of carbon monoxide gives the desired cobalt hydrocarbonyl in the... 

Cobalt is the catalyst most widely employed for hydrocarboxylations and hydroesterifications. The strong similarity to hydroformylation is shown in the catalyst and in the conditions of T and P. In general the three process rates are in the order hydrofor-mylation>hydrocarboxylation>hydroesterification. Like hydroformylation, the high P of CO required, the instability and toxicity of cobalt carbonyl or hydrocarbonyl and the difficulty of catalyst-product separation detract from the overall attractiveness of this reaction . 

Cobalt carbonyl Cobalt hydrocarbonyl Cobalt(lll) 2,4-pentanedioate... 

SYNONYMS Cobalt oxide, cobalt chloride, aquacat, cobalt metal, fume and dust, cobalt carbonyl, cobalt hydrocarbonyl, synonyms vary by compound. 

The reaction in the first stage probably is a homogeneous catalytic reaction, with either cobalt carbonyl or cobalt hydrocarbonyl as the catalyst. The insensitivity to sulfur poisoning, and the fact that any finely divided reactive cobalt compound may be used, agrees well with this assumption. 

Warming pure alkylcobalt tetracarbonyls, or their solutions, to room temperature or above causes a further reaction to take place, producing dialkyl ketones (J). These products can be accounted for by assuming that the acylcobalt tetracarbonyl adds to the alkylcobalt tricarbonyl as cobalt hydrocarbonyl probably adds to an acylcobalt tricarbonyl [Eq. (48)]. The cobalt(III) intermediate could then decompose and form ketone and a mixture of cobalt carbonyls. 

Cobalt carbonyl. See Cobalt tetracarbonyl Cobalt carbonyl hydride. See Cobalt hydrocarbonyl... 

The direction of the addition of the hydrocarbonyl to the olefin may, within certain limitations, be influenced by varying the reaction temperature and CO partial pressure or by replacing CO ligands by other com-plexing agents. As shown by R. F. Heck and D. S. Breslow [35, 759] and by Y. Takegami et al. [58], the olefinic compound itself may exert a strong influence. Under certain conditions the hydrocarbonyl may even be forced to react in the acid form. Thus, at low temperatures isobutylene reacts with hydrocarbonyl to form trimethylacetyl cobalt carbonyl [35, 759] nearly exclusively. The acyl compound could be trapped with triphenylphosphine. It reacted with methanol to form methyl trimethylacetate. 

All the named compounds form cobalt carbonyls under the reaction conditions applied in the oxo reaction. These carbonyls are in equilibrium with cobalt hydrocarbonyl [823] which is the active catalyst in the oxo reaction [30,108,109, 760] see also page 4—6. Since dicobalt octacarbonyl is readily transformed into cobalt hydrocarbonyl, it is often used as a promoter in combination with other cobalt compounds. 

The acyl cobalt carbonyls are very probably then hydrogenated to aldehydes and cobalt hydrocarbonyl, in analogy to the described mechanism for the olefins. As Yokokawa, et al. [298] found, the yield depends strongly on the reaction temperature. At higher temperatures (see table 23), isomerization of the epoxides to the corresponding ketones and aldehydes frequently occurs first. Further reaction gives a large number of polymeric products. 

If the total pressure is low or the olefin excess high, the concentration of cobalt hydrocarbonyl and hydrogen will be reduced and, according to a mechanism proposed by Bertrand et al. [320], the acyl compound can react with the alkyl cobalt carbonyl instead of with hydrogen or cobalt hydrocarbonyl. The ketone is then formed as a result of this reaction. 

Often the aldehyde is hydrogenated to the corresponding alcohol. In general, addition of carbon monoxide to a substrate is referred to as carbonylation, but when the substrate is an olefin it is also known as hydroformylation. The eady work on the 0x0 synthesis was done with cobalt hydrocarbonyl complexes, but in 1976 a low pressure rhodium-cataly2ed process was commerciali2ed that gave greater selectivity to linear aldehydes and fewer coproducts. 

By analogy to nickel carbonyl, acute effects from animal exposures are expected to be pulmonary edema, congestion, and hemorrhage. In humans, nickel carbonyl causes an acute flulike syndrome that subsides and is followed after 12-36 hours by an acute respiratory syndrome. Exposure to cobalt hydrocarbonyl may be expected to produce similar effects. 

One process that capitalizes on butadiene, synthesis gas, and methanol as raw materials is BASF s two-step hydrocarbonylation route to adipic acid(3-7). The butadiene in the C4 cut from an olefin plant steam cracker is transformed by a two-stage carbonylation with carbon monoxide and methanol into adipic acid dimethyl ester. Hydrolysis converts the diester into adipic acid. BASF is now engineering a 130 million pound per year commercial plant based on this technology(8,9). Technology drawbacks include a requirement for severe pressure (>4500 psig) in the first cobalt catalyzed carbonylation step and dimethyl adipate separation from branched diester isomers formed in the second carbonylation step. 

The cobalt is present as a carbonyl derivative and can be directly active in the hydrocarbonylation steps of the process only when a large excess of cobalt is used in the presence of phosphine ligands and iodide promoters (Co/Ru 10/1). In this case the ruthenium is probably mainly involved in the hydrogenation of the aldehydes and their acetals to alcohols (O. 

The formation of formate esters in the hydroformylation reaction (90, 64) may be explained by a CO-alkoxide insertion reaction as well as by the CO-hydride insertion mechanism mentioned above. Aldehydes formed in the hydroformylation reaction can be reduced by cobalt hydrocarbonyl (27) presumably by way of an addition of the hydride to the carbonyl group (90, 2). If the intermediate in the reduction is an alkoxycobalt carbonyl, carbon monoxide insertion followed by hydrogenation would give formate esters (90, 64). 

Metal Hydrides. It is likely that the reduction of aldehydes to alcohols by cobalt hydrocarbonyl (27) is an example of a carbonyl insertion reaction with a metal hydride. It is not clear which way the hydrocarbonyl adds to the carbonyl groups —whether it forms a cobalt-carbon bond (2), or a cobalt-oxygen bond (90). 

If the formation of formate esters under hydroformylation conditions involves the carbonylation of an alkoxycobalt carbonyl as suggested previously (90), this would be evidence that cobalt hydrocarbonyl adds the reverse way to acyl groups. Since the formation of formate esters can be explained as well by a CO insertion into a cobalt-hydrogen group followed by alcoholysis, however, the data would be explained best if a cobalt-carbon bond was formed in the hydride reduction of acyl compounds. 

Figure F shows some acetylene insertion reactions. These, too, are similar to the olefin insertion reactions. The manganese and cobalt hydrocarbonyls again add. Chloronickelcarbonyl hydride, which I believe is an intermediate in many of the nickel carbonyl-catalyzed reactions, adds to olefins. Diborane and the aluminum hydrides also add.

Cobalt hydrocarbonyl, diborane, and aluminum hydrides add, I think, to all of these carbonyl compounds. Of course, there is the well known Grignard reagent and the alkyllithium additions to carbonyl compounds. Aluminum alkyls add, and we could have listed all the other alkali metal alkyls. Recent work has shown that the tin alkoxides add readily to all these derivatives, and similarly, a tin amide adds to most of these carbonyl compounds. 

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