Cobaltcarbonyls

The a complex (a) obtained by cis addition of the cobaltcarbonyl hydride (path A) can either lead to the expected threo aldehyde (path B) or isomerize through a new tt complex ( tt ) path C, to give aldehyde 27. The other possible o- complex (hydride addition (path D) must isomerize to undergo a CO insertion. It can do this through a tt complex (tt") (path E) to give as a final product the erythro aldehyde or through a tt complex ( tt " ) (path F) leading to aldehyde 26. 

The absence of free isomerized olefins, the Constance of isomeric composition of the products throughout the whole reaction in hydro-formylation experiments of 1-pentene and 4-methyl-1-pentene under high carbon monoxide pressure, the distribution of deuterium in the hydro-formylation products of 3-methyl-l-hexene-3-di and 3-(methyl-d3)-l-butene-4-d3, and the results of carbonylation of olefins containing a quaternary carbon atom indicate initial formation of an olefin-cobaltcarbonyl complex. Isomerization of this complex, resulting in 1,2 hydrogen shifts in its organic moiety, can produce the necessary precursors of the various aldehydes that are formed. 

In the presence of 3-8 mol equiv. of pyridine as ligand (compared with Co) the phenomenon of ligand-accelerated catalysis [8] is observed with higher activity and improved selectivity of the catalyst system [9]. The cobaltcarbonyl/ pyridine catalyst system is applied industrially for the synthesis of higher alkanoic acids, e.g., the hydrocarboxylation of isomers of undecene yields dodecanoic acid with approximately 80% selectivity [10],... 

Hydrocarboxylation of the Ce-Cs a-olefins with cobaltcarbonyl/pyridine catalysts at 200 °C and 20 MPa gives predominantly the linear carboxylic acids. The acids and their esters are used as additives for lubricants. The Ce-Cio a-olefins are hydroformylated to odd-numbered linear primary alcohols, which are converted to polyvinylchloride (PVC) plasticizers with phthalic anhydride. Oligomerization of (preferably) 1 -decene, applying BF3 catalysts, gives oligomers used as synthetic lubricants known as poly-a-olefins (PAO) or synthetic hydrocarbons (SHC) [11, 12]. The C10-C12 a-olefins can be epoxidized by peracids this opens up a route to bifunctional derivatives or ethoxylates as nonionic surfactants [13]. 

Catecholborane, as an achiral co- reagent, has also been recommended for the reductions of ketophosphonates [ML2, ML4J, a p-aminosubstituted a-enone [LOl], cyclopropylisopropylketone 3.73, some cobaltcarbonyl complexed ynones 3.74, and unsymmetrically substituted benzophenones 3.75 [CH6, CH7J (Figure 3.26). The reduction of 2,2-diphenylcyclopentanone 3.76 by (5)-3.71 (Ar = Ph, R = Me) leads... 

Some acrylylcobalt carbonyl derivatives have been investigated. Treatment of Na[Co(CO)4] with acrylyl chloride appears to give an unstable acrylylcobalt tricarbonyl derivative which could not be isolated in the pure state but which was identified from its infrared spectrum 239). If this acrylylcobalt carbonyl complex is treated in situ with triphenylphosphine, evolution of one mole of carbon monoxide occurs and the complex CH2= CHCOCo(CO)2P(C6Hs)3 is obtained as a moderately stable yellow solid 242). Similar complexes were observed in the reactions of the crude acrylyl-cobaltcarbonyl complex with triphenylarsine, tri-/>-anisylphosphine, tri-butylphosphine, and trimethyl phosphite, but these were not isolated in the pure state (239). Treatment of Na[Co(CO)4] with acrylyl chloride under much more vigorous conditions gives a low yield of a purple compound CH2=CHCCo3(CO)9 117) related to compounds discussed below. 

In around 1925, the Fisher-Tropsh process, which synthesizes mainly liquid hydrocarbons by the reaction of carbon monoxide with hydrogen at 180-300 C and under 1—300 atm in the presence of nickel, cobalt and iron compounds as catalysts, was developed [81,81a,81b]. This process was used as the process for synthetic petroleum in Germany. However, at present, the production has been continued only in South Africa as state policy. This reaction is revealed to have the action of metal carbonyls as intermediates of the catalysts. In 1938, Roden [82] developed the 0X0 process which produced aldehydes by the reaction of olefins with carbon monoxide and hydrogen in the presence of cobaltcarbonyl type catalysts. 

In the Pauson-Khand reaction one acetylene, one olefin and cobaltcarbonyl (as a carbon monoxide source) are used and cyclopentenone is obtained by a [2 + 2 -t-1 ] cyclization addition [56-61]. As shown in Scheme 17.5, the Pauson-Khand reaction is, at first, two -electrons of the reactive acetylene bond to two cobalt atoms (Figure 17.6), then the olefin coordinates to one cobalt atom and then inserts into the cobalt-carbon bond. Further, one carbonyl inserts into the new cobalt-carbon bond, and cyclopentenone is obtained by elimination of Co2(CO)6 [56]. 

Cobaltcarbonyls are used as catalysts for carbonylations such as hydroformylation (0x0 reaction), hydrocarbonylation and amidocarbonylation [70a]. Hydroformylation is the reaction of preparing aliphatic aldehydes in which carbon number is increased by one [46]. Especially, butylaldehyde has been industrially produced largely from propylene butylaldehyde is used as a raw material for butanol and 2-ethylhexanol, etc. Cobalt and rhodium compounds are used for their catalysts. The reactivity of cobalt catalysts is lower than that of rhodium catalysts. However, more linear products of the reaction shown in eq. (17.27) are obtained. The ratio of... 

Cobaltcarbonyls are used for the carbonylation of benzyl halides or aromatic halides [74-76]. For example, as shown in eq. (17.31), benzylcarboxylic acid is prepared by the reaction of benzyl halide with carbon monoxide. The reaction mechanism is thought to be as follows at first the halogen atom of the halide is substituted by a cobalt atom and the Co-C bond formed is inserted into by a carbonyl. The phenylacetic acid is industrially produced by using this cobalt catalyst [77]. On aromatic halides, not only monocarbonylation but also double carbonylation is liable to proceed [74,75]. 

However, at the end of the oxo reaction when there is no unconverted olefin left to trap the hydrocarbonyl but only acylcarbonyl, the hydrocarbonyl may to a certain extent act as hydrogenating agent. This assumption is supported by investigations of L. Marko et aL [37] who could not find any cobalt hydrocarbonyl in the crude oxo product as long as acyl-cobaltcarbonyl was present. On the other hand they found 02(00)5, probably formed according to (6 a) and (6) + (7). But this result cannot be regarded as final proof since the hydrocarbonyl can also well be trapped by aldehyde already formed at this stage of the reaction (see chapter 1.9). 

Obviously the cobalt, once added to the olefin in the form of its hydrocarbonyl, tends to migrate to the end of the carbon chain since this is thermally and energetically the most favored isomer among the possible alkyl-cobaltcarbonyls [68]. It has already been mentioned that also the terminal 7c-complexes are more stable than the internal ones [69]. Heck and Breslow [35] proposed the following mechanism for this isomerization (see footnote on page 9). 

As described by H. W. Sternberg [440], hydrocarboxylation of acetylenes is possible also in alkaline medium, where (Ni3(CO)8) is believed to function as the CO-donor. Thus, Sternberg obtained 25 % of trans-a-phenyl cinnamic acid besides 67 % of tetraphenyl butadiene, starting from diphenyl acetylene. Starting with octynes J. M. J. Tetteroo reported a considerably lower yield [146]. As mentioned on page 83, different reaction products are obtained with Co- or Fe-carbonyls on the one hand and Ni(CO)4 on the other hand. Contrary to nickelcarbonyl, cobaltcarbonyls are of such activity that the initially formed unsaturated acids are hydrocarboxylated a second time at the double bond. Thus, dicarboxylic acids or their derivatives are obtained by hydrocarboxylation of acetylenes with cobaltcarbonyls as catalysts [226, 388-391, 393-397, 441] (see also table 39). 

Metalcarbonyls, organo- s. Acyl-cobaltcarbonyl complexes Metal complex compounds cobalt porphyrin complexes complex salts manganese complex compounds, ar. metalcarbonyl, organo-metallocenes... 

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