Reactions of High-Nuclearity Carbonyl Clusters

In attempting to rationalize the reactivity of HNCC one faces an extremely complex problem. Compared with the boranes, which have been the subject of detailed electron-density calculations, our knowledge of the electronic properties of HNCC is still insufficient for correlations with reactivity patterns and prediction of the nature and structure of the products. 

For all these reasons it is difficult to suggest mechanisms for reactions of HNCC on the basis of product distribution and structure. These problems cannot be resolved readily. At present there is a paucity of kinetic data available and it may be that because of the complexity of these reactions such data will not be forthcoming. Nevertheless this is clearly an area where further studies are necessary. 

Because of the difficulties discussed above, our classification of the reactions of HNCC is based on the products obtained from those reactions. They are discussed in six separate sections A. Oxidation Reactions, B. Protonation and Deprotonation Reactions, C. Reduction Reactions, D. Electron-Transfer Reactions and Electrochemical Studies, E. Reactions with Soft Nucleophiles, and F. Oxidative Addition of the Small Molecules H2,12, and HX. 

Oxidation of HNCC often results in cluster fragmentation or, as a consequence of redox condensation, cluster expansion as discussed in Section II,B,3. The systematic formation of oxidized species of unchanged nuclearity has been investigated only recently. Depending on the reagent, the products of oxidation reactions may or may not incorporate the oxidant and these reactions are classified below accordingly. 

Oxidation of HNCC Anions without Incorporation of the Oxidant 

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