Molecular clusters, in the broad sense that the term is commonly understood, today comprise an enormous class of species extending into virtually every important area of chemistry: "naked" metal clusters, transition metal carbonyl clusters, hydrocarbon cages such as cubane (C H ) and dodecahedrane (C H ), 8 8 20 20 organometallic cluster complexes, enzymes containing Fe S or MoFe S 4 4 3 4 cores, high polymers based on carborane units, and, of course, the many kinds of polyhedral borane species. So large is the area spanned by these diverse classes that any attempt to deal with them...