Dicobalt octacarbonyl properties

A somewhat related process, the cobalt-mediated synthesis of symmetrical benzo-phenones from aryl iodides and dicobalt octacarbonyl, is shown in Scheme 6.49 [100]. Here, dicobalt octacarbonyl is used as a combined Ar-I bond activator and carbon monoxide source. Employing acetonitrile as solvent, a variety of aryl iodides with different steric and electronic properties underwent the carbonylative coupling in excellent yields. Remarkably, in several cases, microwave irradiation for just 6 s was sufficient to achieve full conversion An inert atmosphere, a base or other additives were all unnecessary. No conversion occurred in the absence of heating, regardless of the reaction time. However, equally high yields could be achieved by heating the reaction mixture in an oil bath for 2 min. 

In the present review we shall describe recent developments in the catalysis of reactions by dicobalt octacarbonyl. Although many of the reactions to be described do not necessarily involve dicobalt octacarbonyl directly in the catalytic cycle, but some derivative, there are several reasons for choosing this compound as a starting point. The most important reason being that dicobalt octacarbonyl is a reasonably stable, commercially available, fairly well characterized compound which easily gives active catalytic intermediates. Although by no means unique in their catalytic properties, the cobalt carbonyls do provide a particularly active and versatile example of metal carbonyl catalysis. Their catalytic reactions are also by far the most investigated and best understood. 

IV. Properties, Structure, and Preparation of Dicobalt Octacarbonyl and Cobalt... 

Certain of the properties of cobalt tetracarbonyl hydride have been summarized previously.4 The pure compound decomposes thermally by a second-order process5 to hydrogen and dicobalt octacarbonyl. The compound is strongly... 

Group 9 metals (Co, Rh, Ir) have been the subject of much interest because of their known catalytic properties. Dicobalt octacarbonyl, Co2(CO)s, can be trapped in zeolites and undergoes various transformations leading to polynuclear Co4(CO)i2, anionic [Co(CO)4] and other species [259-263]. Thermal decarbonylation of 7 -C5H5Co(CO)2 [264] and (CO)4CoSnMe3 [265, 266] in zeolites has also been investigated. 

Discuss the preparation, properties and structure of dicobalt octacarbonyl. 

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