Skeletal Isomerism in Transition Metal Clusters

Oriol Rossell, Miquel Seco, and Gldria Segales 

Several reports dealing with metal-cluster isomerism and possible mechanisms of polyhedral rearrangements have recently been published. Although work in this field was first undertaken by Braunstein in 1991,no further studies have subsequently appeared. Given the increasing interest in cluster isomerism, the purpose of this article is to provide an updated systematic classification to facilitate the study of this area. 

Positional or permutational isomerism occurs in compounds which have the same metal skeletal framework but differ in the occupation of the vertices of the poly-hedron, for example, complexes C and D (Fig. 2).  

Ligand isomerism is observed in compounds that have the same stoichiometry and metal core, but in which two or more ligands formally interchange coordination sites, for example compounds E and F (Fig. 

Note that for positional and ligand isomerism neither the core geometry nor the electron count changes on rearrangement from one isomer to another. 

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