Redox potentials of oligomeric metal clusters

The observation of an effective transfer from S to M implies that the potential of the critical cluster is at least slightly more positive than that of the electron donor system., i.e. E°(M//M ) E°(S/S ). 

Clusters M may also behave as electron donors when formed in the presence of oxidizing reactants. For example, as far as n n, the electron transfer from M to S is possible since E°(M /M ) E°(S/S )  

This cascade of reactions (corrosion process) is generally slow with respect to (27-29) due to the step of IS/F release (31). However, it is observed when the coalescence (14) is also slow. For example, it was found that during the very slow coalescence of Ag in a Nafion membrane, controlled by the slow diffusion between the cavities (10 1 mol s ) , the smallest clusters could be 

Reference system (electron donor) E°(S/S ) (ref. couple) NHE/ Metal cluster (electron acceptor) (reduced atoms/cluster) 

E°(Agg /Ag8) E°(H30 /H2) = 0 Vnhe- Note that such a corrosion by H30 is not observed under conditions of free diffusion of the clusters as in Ag solutions, because the coalescence let grow much faster the clusters up to the supercritical nuclearities. 

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