“…The family of compounds derived by chemical modification of these species led to numerous publications in this field − and the discovery of other cluster compounds composed of other cluster building elements with ligands other than the halides. − An important inspiration for this was the discovery of strong metal−metal bonds by Cotton in the early 1960s, especially with respect to bonding theory and numerical calculations of the electronic structures. − Not only because of the aesthetic nature of these structures and the interesting chemistry of these compounds, but also due to their importance in the field of photochemistry, − and even more so, their strong potential in catalysis, − this area is of high actuality. Because a plethora of these compounds is known, the ensuing discussion will be limited to spectroscopic investigations of octahedral clusters with mixed-halide coordination spheres or mixed-metal cages.…”