Cage-Bonded Metallacarbaboranes

In some metallacarbaborane clusters, a metal fragment is supported on the outside of the carbaborane skeleton, typically by B H M interactions, for example, complex (27) involves exo interactions between the T1(I) atom of one cage and two terminal boron hydrogen bonds of a second cage. The exo descriptor illustrates the relationship of the metal fragment to the carbaborane and the nido descriptor classifies the carbaborane cage. 

Exo-nido metallacarbaborane complexes are at present comparatively rare, but are nevertheless a clear bonding option by which a number of metal-ligand fragments may interact with a C2B9 cage system. However, the species 62 are singled out from all other known examples by having... 

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