Two-dimensional oxides constructed from octamolybdate clusters and M ⁿ⁺/tetrapyridylpyrazine subunits (M = Co, Ni: N = 2; M = Cu: N = 1)

Hydrothermal methods have allowed the preparation of three two-dimensional materials constructed from octamolybdate clusters and secondary metal/tetra-2-pyridylpyrazine subunits. The δ-Mo8O264- cluster of [{Cu₂(tpyprz)}₂Mo₈O₂₆] is illustrated. The hydrothermal reactions of MoO₃, tetra-2- pyridylpyrazine (tpyprz) and M(CH₃CO₂)₂ • 2H₂O (M = Co, Ni) yielded the two-dimensional oxides [M ₂(tpyprz)(H₂O)₂Mo₈O₂₆] • xH₂O [M = Co, x = 1.8 (1); M = Ni, x = 0.6 (2)]. However, the reaction of (NH₄)₆Mo₇O₂₄ • 4H₂O, tpyprz and Cu(CH₃CO₂)₂ • H₂O produced [{Cu₂(tpyprz)}₂Mo ₈O₂₆] • 2H₂O (3 • 2H₂O). The isomorphous structures of 1 and 2 are constructed from α-Mo8O264- clusters linked through {M₂(tpyprz)(H₂O)₂} ⁴⁺ subunits into two-dimensional networks. While the structure of 3 is also two-dimensional, the molybdate building block is present as the δ-isomer and the secondary-metal/ligand component consists of a one-dimensional {Cu2(tpyprz)}n2n+ chain. The structure of 3 is compared to that of the previously reported three-dimensional material [{Cu₂(tpyprz)} ₂Mo₈O₂₆] • 7H₂O which contains ζ-Mo8O264-clusters and structurally distinct {Cu2(tpyprz)}n2n+ chains.