A new tetra-Zr(iv)-substituted polyoxotungstate aggregate

Abstract

A new tetra-Zr-substituted tungstophosphate (TP), [H₂N(CH₃)₂]₆Na₆H₈{Zr₂[SbP₂W₄(OH)₂O₂₁][α₂-PW₁₀O₃₈]}₂·50H₂O (1), has been made by the hydrothermal reaction of the [B-α-SbW₉O₃₃]⁹⁻ building block with Zr⁴⁺ cations and PO₄³⁻ anions in the presence of dimethylamine hydrochloride and NaOAc–HOAc (pH = 4.8), and further characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), ³¹P NMR spectroscopy and single-crystal X-ray diffraction. 1 is a toroidal structure formed by two divacant [α₂-PW₁₀O₃₈]¹¹⁻ units and two [SbP₂W₄(OH)₂O₂₁]⁷⁻ fragments linked by four Zr⁴⁺ cations. Note that the TP is reassembled with tetrahedral PO₄ replacing the triangular pyramidal SbO₃ in the [B-α-SbW₉O₃₃]⁹⁻ precursor. In addition, the pendant SbO₃ derives from the dissociation of the [B-α-SbW₉O₃₃]⁹⁻ precursor. Furthermore, the electrochemical properties of 1 have been studied in Na₂SO₄ + H₂SO₄ supporting electrolyte (0.5 mol L⁻¹), and indicate that 1 exhibits apparent catalytic activity toward H₂O₂ and BrO₃⁻ reduction. The ³¹P NMR spectrum of 1 exhibits three signals with approximately proportional intensities, which is consistent with the solid-state structure.