Can M6X8 clusters form intercluster metal metal bonds?

M6X8 clusters are always found to form exo bonds to donor ligands. This behavior is simply understood in terms of the electronic structure of the cluster core: the LUMO orbitals of the clusters have a -acceptor character. These relatively low-lying orbitals should be available for intercluster metal-metal bond formation providing species can be made that have a formal cluster d-electron count greater than 24. Cluster dimers should be stable for 25 electrons per cluster, and 26 electrons per cluster is favorable for one-dimensional polymers. A cubic Chevrel phase alternative structure utilizing M608 clusters is promising in that the steric requirements of the oxo clusters allow the tight packing necessary for intercluster metal-metal bonding. A sampling of molecules and extended systems is treated, and analogies are drawn with known or potential B6 species. 1986, American Chemical Society. All rights reserved.

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