Mg2Na2V10O28·20H2O and Mg3V10O28·28H2O

The crystal structures of dimagnesium disodium decavanadate icosahydrate, Mg₂Na₂V₁₀O₂₈·20H₂O, (I), and trimagnesium decavanadate octacosahydrate, Mg₃V₁₀O₂₈·28H₂O, (II), have been determined by single‐crystal X‐ray diffraction. They crystallize with monoclinic (C2/c) and triclinic () symmetry, respectively. All the Mg²⁺ cations in (I) and (II) are octahedrally coordinated by six water mol­ecules. The Na⁺ cations in (I) are coordinated by three water mol­ecules and three O atoms of the decavanadate anions, and link the latter into a three‐dimensional network. The decavanadate anions in (II) are not linked to one another.     

Cu3V10O28·24H2O and CuNa4V10O28·23H2O

The crystal structures of tricopper decavanadate tetracosa­hydrate, (I), and copper tetra­sodium decavanadate tricosa­hydrate, (II), have been determined by single‐crystal X‐ray diffraction. Both compounds exhibit a catenary structure consisting of [V₁₀O₂₈]⁶⁻ anions linked by Cu²⁺ cations in (I) or by Na⁺ cations in (II). Compound (II) also contains a polymeric linear array of edge‐sharing [Na(OH₂)₆]⁺ and [Cu(OH₂)₆]²⁺ octahedra. In both compounds, the [V₁₀O₂₈]⁶⁻ ions lie about inversion centres and the Cu²⁺ ions in (I) also lie about inversion centers.