Isomerization, polyhedral, metal cluster

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. 

A brief review of graph-theoretical ideas is to be found in Mathematical methods in coordination chemistry topological and graph-theoretical ideas in the study of metal clusters and polyhedral isomerizations by R. B. King, Coord. Chem. Rev. (1993) 122, 91. 

Further expansion of 13-vertex species or thermal metal transfer reactions leads to the 14-vertex cluster [(T -C H )Co]2C2B2qH22 [52649-56-6] and [52649-57-7] (199). Similar 14-vertex species have been obtained from tetracarbaboranes (203) and show unusual stmctures. The isomeric bimetallic cobaltacarborane complexes /(9j (9-(Tj -CpCo)2C2BgH2Q (cp = C H ) can be formed by either polyhedral expansion or contraction reactions. Six isomers of this cluster are formed in the thermally-induced intermolecular metal transfer and polyhedral expansion of the 11-vertex f/oj o-(ri -C H )CoC2BgH Q. 

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