摘要：

While the number of polynuclear transition metal complexes reported continues to grow rapidly, some nuclearities remain rare. Heptanuclear complexes are particularly uncommon, for example for cobalt there are a number of heptanuclear carbonyl 1and sulfide-bridged 2clusters but no examples of heptanuclear cages containing N- or O-donors. Cobalt is the most extreme example, but there are few heptanuclear cages for the other first row metals. The structures displayed by these heptanuclear cages are mostly irregular. There are a number of “metallocrowns”, where six metals and their ligands encapsulate a seventh metal in a similar manner to the way a crown ether co-ordinates. The earliest example of this motif is found for titanium,3with more recent examples reported for copper,4titanium,5manganese,6,7nickel,8and zinc.9There are also a number of examples of vertex-sharing double cubanes for copper 10and zinc,11and two examples from zinc chemistry where oxo-centred vertex-sharing bitetrahedra are found,12but the majority 13of compounds have no easily describable core.Here we report three heptanuclear cobalt cages and two examples where these heptanuclear fragments are linked into larger oligomers. A preliminary account of two of the structures has been published previously.14A further challenge in this field is to discover an underlying structural principle that will allow rationalisation of the structures observed. Here we show that a wide range of structures can be derived from the mineral Co(OH)2, allowing for some distortions in the lattice.

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