Crystal structure of a new magnesium paratungstate salt (CH3NH3)4[(Mg(H2O)5)2H6W12O42]Br2·8H2O

Abstract

The X-ray crystal structure of (CH₃NH₃)₄[(Mg(H₂O)₅)₂(H₆W₁₂O₄₂)]Br₂·8H₂O (1) obtained by a reaction of Li₂WO₄·H₂O and Mg(NO₃)₂·6H₂O in the presence of MeNH₃Br is reported. Crystallographic parameters are: triclinic, space group P-1, a = 10.8280(4) Å, b = 12.4866(5) Å, c = 12.6201(5) Å, α = 108.501(1)°, β = 111.542(1)°, γ = 91.139(1)°, V = 1486.98(10) ų, Z = 1, C₄H₆₆Br₂Mg₂N₄O₆₀W₁₂, d_x = 3.959 g/cm³, T = 150 K, R₁ = 0.030 for 9914 F_o > 4δ(F) until 2θ_max = 66.6° The structure contains tetraprotonated [H₂W₁₂O₄₂]^10– anions coordinated with {Mg(H₂O)₅}²⁺ cations as ditopic ligands via terminal oxygen atoms. The crystal structure also incorporates outer-sphere CH₃NH₃⁺ and Br^– ions. The Mg²⁺ cations are in the octahedral environment, Mg–O(H₂O) and Mg–O(W) bond lengths being 2.102(5)÷2.044(5) Å and 2.071(5) Å, respectively.