Octahedral coordination vertex-sharing

A further decrease in the X Me ratio, to 4, leads to linkage of the octahedral units by sharing more than one ligand so as to achieve coordination saturation. Sharing of two vertexes (two comers of the each octahedron) leads to the formation of compounds with layered-type structures. 

Structure (7c), two cubanes sharing a metal vertex with M(p3-X)6 octahedral coordination, is confirmed for Me4Zn7(OMe)8 and Et6Zn7(OMe)8.270 Structure (7d), which occurs in (p3-NMe)7-(AlMe)7271 with virtual C3v symmetry, is envisaged as two (MeNAlMe)4 cubanes, one excised of an AlMe vertex and the other excised of an NMe vertex, and connected on the resulting triangular faces by three A1—N bonds. 

In both the dodecahydrate and decahydrate stmctures, the interlayer cation is coordinated by six H2O groups, and a network of hydrogen bonding connects the interlayer octahedrato the sheets (Fig. 34). In the octahydrate structure (e.g., metakahlerite), the octahedral coordination of the interlayer cation consists of five interlayer H2O groups, whereas the sixth vertex is a shared O atom of a dioxo group of a uranyl square bipyramid [138]. 

The structures of compounds AX2 with octahedral coordination of A are of interest in connection with the theorem , stated on p. 158, that if three regular octahedral groups AXg have a common vertex at least one edge (or face) must be shared if reasonable distances are to be maintained between X atoms of different... 

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