Solution Species and Crystal Structure of Zr(IV) Acetate

Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr₄(OH)₈(OH₂)₁₆]⁸⁺ to a hexanuclear acetate species Zr₆(O)₄(OH)₄(CH₃COO)₁₂. The solution species Zr₆(O)₄(OH)₄(CH₃COO)₁₂ was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr₆(μ₃-O)₄(μ₃-OH)₄(CH₃COO)₁₂·8.5H₂O. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical.