An Unusual Asymmetric Polyoxomolybdate Containing Mixed-Valence Antimony and Its Derivatives: [Sb₄^VSb₂^IIIMo₁₈O₇₃(H₂O)₂]¹²⁻ and {M(H₂O)₂[Sb₄^VSb₂^IIIMo₁₈O₇₃(H₂O)₂]₂}²²⁻ (M = Mn^II, Fe^II, Cu^II or Co^II)

A new type of heteropolyanion containing mixed-valence antimony, [Sb₄^VSb₂^IIIMo₁₈O₇₃(H₂O)₂]¹²⁻ (1a), and its four derivatives, {M(H₂O)₂[Sb₄^VSb₂^IIIMo₁₈O₇₃(H₂O)₂]₂}²²⁻ (M = Mn^II, Fe^II, Cu^II, or Co^II) (2a−5a), have been isolated as ammonium salt, and their structures were determined by single-crystal X-ray diffraction. The framework of the polyanion 1a displays a curious asymmetric structure, and there exist six types of Sb coordination environments and seven types of {MoO₆} octahedra. The title compounds were also characterized by elemental analyses, IR, UV–vis, Raman spectra, and cyclic voltammogramms.