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A series of novel isocloso-diiridaboranes [(Cp*Ir)2B6H6], 1, 2; [1,7-(Cp*Ir)2B8H8], 4; [1,4-(Cp*Ir)2B8H8], 5; [(Cp*Ir)2B9H9], 8; isonido-[(Cp*Ir)2B7H7], 3; and 10-vertex cluster [5,7-(Cp*Ir)2B8H12], 6 (Cp* = η5-C5Me5) have been isolated and structurally characterized from the pyrolysis of [Cp*IrCl2]2 and BH3·thf. On the other hand, the corresponding rhodium system afforded 10- and 11-vertices clusters [5-(Cp*Rh)B9H13)], 7, and [(Cp*Rh)2B9H9], 9, respectively. Clusters 1 and 2 are topological isomers. The geometry of 1 is dodecahedral, similar to that of its parent borane [B8H8]2-, in which two of the [BH] vertices are replaced by two [Cp*Ir] fragments. The geometry of 2 can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. Compounds 4 and 5 are 10-vertex isocloso clusters based on a 10-vertex bicapped square antiprism structure. The only difference between them is the presence of a metal-metal bond in 5. The solid-state structures of 8 and 9 attain an 11-vertex geometry in which a unique six-membered B6H6 moiety is bonded to the metal center. In addition, quantum-chemical calculations have been used to provide further insight into the electronic structure and stability of the clusters. All the compounds have been characterized by IR and ¹H, 11B, and 13C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]