The related complex [Co II 2Li6(OH)2(TBC [8])Br2(MeCN)4] (20) can be obtained from the reaction of CoBr2, LiO t Bu and H8TBC [8] in Et2O. The structure of 20 (Fig. ) is very similar to 18 but with the peripheral Li ions and terminal THF molecules being absent. Variations in reaction stoichiometry and reagents appear to play an interesting role in product identity for both 19 and 20, particularly with regard to the Co:Li ratio / positional disorder at the metal sites, such that several non-stoichiometric analogues have been isolated. The sole Na analogue in the family is the complex [Co II 4Na(H4TBC [8])2Br(MeCN)6] (21) made from the reaction of CoBr2, H8TBC [8] and NaH in THF. The structure of 21 (Fig. ) is highly unusual. The metallic skeleton is an irregular polyhedron, perhaps best described as a highly distorted {Co4Na} square based pyramid, with a Co II ion at the apex and the three Co II ions and one Na ion forming the square base. However, not all of these ions are directly connected to each other. The apical Co II ion is linked to one Co II ion in the square base through a µ-bridging Br -ion and one µ-O(Ph) atom. In turn, this Co II ion is bridged to the other Co II ions in the square base via two µ-O(Ph) atoms from the same H4TBC [8] ligand. The remaining five O(Ph) atoms are uncoordinated, sharing four H-bonds, with the ligand adopting a pseudo-chair loop conformation. The second calix [8]arene ligand is also quadruply deprotonated, H4TBC [8], but does not bridge between any metal centres. Instead, it adopts the pleated-loop conformation in which each neighbouring pair of O(Ph) atoms chelate to a single metal centre. A total of four H-bonds are observed between the O(Ph) atoms. The four Co II ions are of three types. Two are four coordinate and in distorted tetrahedral {CoO3N} geometries, the fourth site being occupied by a MeCN molecule. There is an additional long contact to the µ-Br -ion (~3 Å). One Co ion is five coordinate and in a distorted trigonal planar {CoO3NBr} geometry, again coordinating a MeCN molecule. The fourth Co ion is six coordinate and in a distorted octahedral {CoO3N2Br} geometry, with its coordination sphere completed by two MeCN molecules. The Na ion is four coordinate and in a distorted {NaO2BrN} coordination geometry, with another MeCN molecule completing its coordination sphere.