Ammines cobalt carbonate complexes

Keywords Flue gas denitration, NO oxidation, ammine cobalt complex, activated carbon INTRODUCTION... 

In certain instances, the coordinated oxygen atom may undergo reaction. The complete and elegant work carried out on carbonato-ammine complexes of cobalt (III) illustrates this situation. As Equation 34 reveals, the acid hydrolysis of [ (NH3)5CoC03]+ involves substitution at the carbon-oxygen bond, rather than the cobalt-oxygen bond (4). 

Sargeson and his coworkers have developed an area of cobalt(III) coordination chemistry which has enabled the synthesis of complicated multidentate ligands directly around the metal. The basis for all of this chemistry is the high stability of cobalt(III) ammine complexes towards dissociation. Consequently, a coordinated ammonia molecule can be deprotonated with base to produce a coordinated amine anion (or amide anion) which functions as a powerful nucleophile. Such a species can attack carbonyl groups, either in intramolecular or intermolecular processes. Similar reactions can be performed by coordinated primary or secondary amines after deprotonation. The resulting imines coordinated to cobalt(III) show unusually high stability towards hydrolysis, but are reactive towards carbon nucleophiles. While the cobalt(III) ion produces some iminium character, it occupies the normal site of protonation and is attached to the nitrogen atom by a kinetically inert bond, and thus resists hydrolysis. 

The procedure described here is based on the observation that amine monohydroxo complexes of cobalt(III), rhodium(IIl), and iridium(III) react directly with carbon dioxide to form the corresponding carbonato complexes,2 3 without effect on the configuration of the amine ligands.4 The amine monoaqua complex is allowed to react with lithium carbonate or carbon dioxide gas at room temperature at pH 8.0 for a few minutes, and the carbonato complex is isolated by adding alcohol. The procedure has been used to prepare salts of the following cations pentaammine(carbonato)-cobalt(III),2 ds-ammine(carbonato)bis(ethylenediamine)cobalt(III),5 trans-... 

Metal-complex adsorption can directly lead to surface reaction, as has been observed recently for cobalt ammine complexes adsorbing over carbon substrates [41, 42]. The uptake of cobalt hexaammine (CoHA), [(NH3)6Co]+3... 

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