Highly symmetric networks derived from cubane-related octametallic complexes of a new oxyanion of carbon, C4O74-, each molecule attached to eight neighbors by 24 equivalent hydrogen bonds

Aqueous reaction mixtures containing dihydroxyfumaric acid, M2+ (M = Zn, Co, Fe, and Mg) and acetate ion at room temperature give crystals, suitable for single-crystal X-ray diffraction studies, of composition [(MII)8(C4O7)4(H2O)12]·24H2O, in which the C4O74- component is the alkoxide-tricarboxylate tetra-anionic species -OC(CO2-)3, a new oxyanion of carbon. All four compounds crystallize in the body-centered space group I43m with cell dimensions a ≈ 15.0 Å. Discrete electrically neutral [(MII)8(C4O7)4(H2O)12] molecules are present, with a cubane-like core consisting of four trigonal prismatic metal centers and four μ3-alkoxo bridges from separate -OC(CO2-)3 ligands. The octametallic molecule is highly symmetrical, with four fac tri-aqua octahedral metal centers tetrahedrally appended to the central cubane-based [(MII)8(C4O7)4 ]8- unit. The molecules assemble in the crystal in a body-centered cubic fashion, each being attached to its eight neighbors by 24 equivalent hydrogen bonds- an extreme example of self-complementarity. Copyright © 2004 American Chemical Society.