Crystal structure and properties of a new magnesium heteropoly-tungstate, Mg7(MgW12O42)(OH)4(H2O)8, and the isostructural compounds of manganese, iron, cobalt and nickel
Abstract Cubic Mg7(MgW12O42)(OH)4(H2O)8 has been prepared in single crystalline form from solution. Isomorphous compounds, in which Mg is replaced by the transition metals Mn, Fe, Co and Ni have been obtained in microcrystalline form by a new reaction method. Colour and lattice constants of the Fe compound indicate that iron is trivalent, whereas all the other heteroelements are divalent. The main building unit of these structures are [MW12O42]10− anions with a metal atom M in a central twelve-coordinated cavity, crosslinked in three dimensions by MO6-octahedra. Crystallographic data for the Mg-compound are: fw=3284.8, space group I m 3 (no. 204), a = 12.862 (2) A , V = 2128 (1) A 3 , Z = 2, Dx = 5.126 g cm−1, μ = 312.28 cm−1, final R = 0.028 for 487 observed reflections. Lattice constants a for the transition metal compounds are: Mn: 13.075 A, Fe: 12.754 A, Co: 12.878 A, Ni: 12.824 A.