Oxidative Fragmentation and Reductive Condensation

When metal carbonyl clusters in zeolite cages are subjected to severe thermal conditions under, for example, vacuum or an O2 atmosphere, complex transformations typically occur. The most commonly observed reactions involve changes in the nuclearity of the organometallic species i.e., fragmentation and/or aggre- 

These results also illustrate the advantages of using zeolite encaged dusters as precursors for well defined metal catalysts. Some encaged clusters appear to be stable to cycling through oxidation and reduction without forming crystallites on the external zeolite surface. 

The available data suggest several hypotheses for how to maximize the stability of metal carbonyl clusters on supports. 

1) Choosing metals which give stable metal frameworks (e.g. Os and Ir). 

2) Using optimum zeolite/metal combinations (e.g. basic NaX zeolite to staUlize cluster anions such as [Irg(CO)i5] ). 

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