By Cobalt Catalysts

C. Aaserud, Model studies of secondary hydrogenation in Fischer-Tropsch synthesis studied by cobalt catalysts, Thesis, NTNU, Trondheim, 2003. 

Transition-metal-promoted cycloaddition is of much interest as a powerful tool for synthesis of carbocyclic stmcture in a single step. Utilization of carbon monoxide as a component of the cycloaddition reaction is now widely known as the Pauson-Khand reaction, which results in cyclopentenone formation starting from an alkyne, an alkene, and carbon monoxide mediated by cobalt catalyst. Although mechanistic understanding is limited, a commonly accepted mechanism is shown in Scheme 4.16. Formation of dicobalt-alkyne complex followed by alkene... 

Other work has shown that cobalt complexes under H2/CO pressure and at higher temperatures can catalytically convert formaldehyde to glycolalde-hyde (76) or ethylene glycol (77-79) methanol is observed as a product as well. It has therefore been well demonstrated that formaldehyde can be converted by cobalt catalysts to the same products observed from CO reduction. 

Table I reports the results of typical polymerization runs of pentadiene by cobalt catalysts prepared from Al(C2H5)Cl2 complexed with thiophene or pyridine. The crude polymerization products obtained by these systems have a cis-1,4 content of about 75-80%. Fractions having a higher cis-1,4 content (about 85%) could be isolated by dissolving the crude polymers in benzene and reprecipitating with methylethyl ketone (MEK). This solvent dissolves only the low molecular weight polymers, which, in this case, have also a low cis-1,4 unit content.

Equation (2) is the actual Fischer-Tropsch reaction of hydrocarbon formation which is best catalyzed by cobalt catalysts, and Equation (3) represents the water-gas shift reaction, which has to be anticipated with Fe catalysts. 

D. E. Morris, G. V. Johnson, Sympos. Rhodium Homogen. Catal., Veszprem, Hungary (1978). 14.6.4.1. by Cobalt Catalysts... 

Thus, little isomerization apparently takes place except perhaps at high 1-pentene conversions. This observation is interesting in view of the work of Ansinger and Berg (5), who reported the isomerization of 1-dodecene by cobalt catalysts at high pressures (100 atm.) of carbon monoxide at 150-160° in the absence of hydrogen. 

Zhong DK, Gamelin DR (2010) Photoelectrochemical water oxidation by cobalt catalyst ( Co-Pi )/a-Fe203 composite photoanodes oxygen evolution and resolution of a kinetic bottleneck. J Am Chem Soc 132 4202-4207... 

Kawatsura M, Hayashi S, Komatsu Y, Hayase S, Itoh T. Enantioselective a-fluorination and chlorination of p-ketoesters by cobalt catalyst. Chem. Lett. 2010 39(5) 466 67. 

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