Multimetallic sandwich compounds

After the seminal discovery of multimetallic sandwich compounds 231 and 232, several palladium [164], platinum [165], and Pd/Pt heterometallic [166] sandwich compounds belonging to the new and burgeoning family were synthesized and characterized. Furthermore, it was found that the assembly of the multimetallic core can be tuned intermolecularly [167] or intramolecularly [168] by redox reactions. It can be foreseen that this novel and unique family of compounds will flourish in the near future and find its own position in catalysis. 

Multimetallic sandwiches, including polymetallocenes, bis(fulvalene)-dimetal compounds, multi-decker sandwiches, and compounds in which two metals are bonded to a common unsaturated cyclic hydrocarbon are discussed in Section II. Sections III and IV are subdivided according to the metal group, and describe ligand-bridged bimetallics and metal clusters, respectively. Where appropriate, redox potentials have been included. Unless otherwise stated they are referenced versus the aqueous saturated calomel electrode (see). 

Although recent reviews of metal-carborane electrochemistry (37, 38) obviate the need to discuss multimetallic carborane clusters here, it seems appropriate to mention the results of studies on triple-decker sandwich compounds. The only structurally confirmed (39) all-hydrocarbon tripledecker, [Ni2Cp3] (18), has apparently not been investigated electro-chemically, but carborane analogues containing two or three boron atoms... 

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