An oxide chain constructed from octamolybdate, a Keggin anion and a copper (II) - Tetrapyridylpyrazine binuclear unit

The hydrothermal reaction of MoO₃, CuSO₄·5H₂O, tetra-4-pyridylpyrazine (tpyprz), and diphenyldiarsonic acid in water at 140 °C for 48 h yielded the one-dimensional material [{Cu₂(tpyprz)(H₂O)₃}₂{Mo₈O₂₆}{Mo₁₂O₃₆(AsO₄)}]·8H₂O (1·8H₂O). The chain structure of 1·8H₂O is constructed from alternating β-octamolybdate clusters and molybdoarsonate Keggin clusters linked through {Cu₂(tpyprz)(H₂O)₃}⁴⁺ binuclear subunits. The Cu(II) sites are inequivalent with one copper bonding to two pyridyl donors and a pyrazine nitrogen of one terminus of the tpyprz ligand, two aqua ligands and an oxo-group of the β - Mo₈ O₂₆^{4 -} cluster while the second copper site coordinates to the nitrogen donors of the other terminus of the tpyprz ligand, an aqua group, a terminal oxo-group of the β - Mo₈ O₂₆^{4 -} cluster and a terminal oxo-group of the mixed valence {Mo₁₁^VIMo^VO₃₆(AsO₄)}^4- cluster. Crystal data: C₄₈H₆₀AsCu₄Mo₂₀N₁₂O₈₀: FW = 4332.96 Triclinic P over(1, ̄), a = 12.5087(5) Å, b = 13.6681(6) Å, c = 14.8980(6) Å, α = 92.196(1)°, β = 97.046(1)°, γ = 97.751(1)°, Z = 1, D_calc = 2.877 g cm^-3; structure solution and refinement based on 12,333 reflections (Mo K_α, λ = 0.71073 Å) converged at R₁ = 0.0540 and wR₂ = 0.1115.