Metal carbonyls cobalt hydrocarbonyl

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

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). 

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. 

Als Katalysatoren eignen sich eine Vielzahl von Ubergangsmetallen. Besondere Bedeutunghaben Nickel, (Cobalt, Rhodium, Palladium, Platin und Eisen. Kupl er, Ruthenium, Osmium und Manganfinden ebenfalls Anwendung. Die eigentlich katalytisch wirksamen Spezies sind Carbonyl- oder Hydrocarbonyl-Komplexe dieser Metalle. 

The conditions for the synthesis must differ, as the electronic configuration of each metal changes, but the intermediate in each case probably is a complex in which acetylene and carbon monoxide are each linked to two metal atoms. Cobalt and iron compounds having both acetylene and carbonyl bridges have already been synthesized 27). The report of the preparation of a dimeric nickel hydrocarbonyl, [NiH(CO)a]2 by Behrens 28) may well lead to the isolation of a siipilar acetylene complex with nickel. 

The carbonyls or hydrocarbonyls of cobalt which are used as catalysts are generally formed in situ by feeding cobalt to the reactor in the form of metal oxide, hydroxide or salt of an organic or inorganic acid, either in solution or suspension in olefin, high boiling distillation residues or water. However, the carbonyls may also be formed in a small carbonyl generating reactor which is fed by the same catalyst precursors before they enter the hydroformylation reactor [161]. 

The following facts support the assumption that the true catalysts are the transition metal hydrocarbonyls rather than the corresponding metal carbonyls. Only metals which can form hydrocarbonyls, like cobalt, rhodium and iron, can act as catalysts [123, 280, 673, 674], whereas nickel, e.g., is inactive [123, 673] in most cases. Furthermore it is known that cobalt, rhodium and iron carbonyls, under the reaction conditions applied, are able to abstract hydrogen from alcohols, amines and even from the unreactive cycloparaffins to form metal hydrocarbonyls [121-124]. 

If the crystalline carbonyl is desired, low-boiling (30-60°) petroleum ether should be substituted for benzene in the above preparation. The petroleum-ether solution of the carbonyl is cooled overnight in the refrigerator, whereupon the crystalline dicobalt octacarbonyl separates. The solvent is decanted and the solid poured onto filter paper and then bottled. The carbonyl can be prepared directly in the crystalline form from metallic cobalt with carbon monoxide in the presence of 1 atm. of hydrogen sulfide. Some hydrocarbonyl is formed however. The crystalline carbonyl also can be prepared in a dry state from cobalt(II)-sulfide at 200° with carbon monoxide at 200 atm. if a metal like copper is present to combine with sulfur (Hieber, Schulten, and Marin, 42). 

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