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 [{Cu ₂(tpyprz)} ₂Mo ₈O ₂₆] is illustrated. The hydrothermal reactions of MoO ₃, tetra-2- pyridylpyrazine (tpyprz) and M(CH ₃CO ₂) ₂ • 2H ₂O (M = Co, Ni) yielded the two-dimensional oxides [M ₂(tpyprz)(H ₂O) ₂Mo ₈O ₂₆] • xH ₂O [M = Co, x = 1.8 (1); M = Ni, x = 0.6 (2)]. However, the reaction of (NH ₄) ₆Mo ₇O ₂₄ • 4H ₂O, tpyprz and Cu(CH ₃CO ₂) ₂ • H ₂O produced [{Cu ₂(tpyprz)} ₂Mo ₈O ₂₆] • 2H ₂O (3 • 2H ₂O). The isomorphous structures of 1 and 2 are constructed from α-Mo8O264- clusters linked through {M ₂(tpyprz)(H ₂O) 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 [{Cu ₂(tpyprz)} ₂Mo ₈O ₂₆] • 7H ₂O which contains ζ-Mo8O264-clusters and structurally distinct {Cu2(tpyprz)}n2n+ chains.