The Preparation and Characterization of Two New Heteropolyoxofluorotungstate Anions [CuNiW₁₁O₃₈F₂H₄]⁴-and [NiMnW₁₁O₃₈F₂H₄)⁴-

Abstract

The ammonium salts of [CuNiW₁₁O₃₈F₂H₄]⁴-and [NiMnW₁₁O₃₈F₂H₄)⁴-have been isolated in the crystalline form. Studies of X-ray powder patterns reveal that both compounds are isomorphous. Other evidence from analytical results, FABMS, spectroscopy (Vis., I.R.), and cyclic voltammetry has shown that the structures are a modification of the well known “Keggin” structure. One of the heteroatoms in either compound is thought to occupy the octahedral site vacated by the missing tungsten atom, and the other heteroatom occupies the central tetrahedral cavity. The magnetic susceptibility per gram of (NH₄)₄CuNiW₁₁O₃₈F₂H₄·3H₂O is 1.20 × 10⁻⁶, and that of (NH₄)₄NiMnW₁₁O₃₈F₂H₄·3H₂O is 3.46 × 10⁻⁶, indicating four unpaired electrons present in the latter. The FABMS shows that the formula weights of the anhydrous salts are 2721 and 2719 for the CuNi and NiMn compounds, respectively.