Complexes of higher nuclearities

Very interesting and detailed oxidation patterns have been obtained for the dinuclear species [(bpy)2Ru(2,3-dpp)Ru(bpy)2]4+ (Ru2) and [(bpy)2Ru(2,5-dpp) Ru(bpy)2]4+ (Ru2a)21,22 (see Fig. 5.3 and Table 5.1), which contain a relatively small number of redox centers and can be considered as the most effective model compounds to understand the electrochemistry of the complexes of higher nuclearity. In the dinuclear species, the knowledge of the voltammetric behavior of the mononuclear building blocks allowed to establish the localization for each redox process and to evaluate the mutual interactions existing between the redox sites. 

As on other occasions, the reaction of a metallic complex, such as the trinuclear [p-S Au2(p-dppf) (dppf = l,l/-bis(diphenylphosphino)ferrocene), with [Au(C6F5) (tht)] leads to the preparation of a new organometallic gold complex of higher nuclearity, [ x3-S Au(C6F5) Au2(p-dppf) ] [Eq. (47)], in which the sulfur atom bridges the three gold centers.148... 

These compounds do not belong to the family of cluster complexes in a classical sense, but they are mentioned here for systematic reasons. For the synthetic chemist, they are very useful precursors for building up complexes of higher nuclearities. 

As can be seen, in these trinuelear complexes there are still potential donor centers (the metal center in the palladium derivative or the C(2) atom in the platinum compound), so that one would think that complexes of higher nuclearity could be obtained if the reactions between the acac complexes and Ag(C104) were to be carried out with a higher proportion of silver. Flowever, the results once again depend on the metal center (Pd or Pt). For the palladium compound the reaction only takes place in a 2 1 molar ratio and the trinuelear derivative is again obtained (Eq. 

For the synthesis of dendritic complexes of higher nuclearity, polynuclear arms must be used in reaction (1). 

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