Synthesis, Magnetism, and Electrochemistry of the Ni₁₄- and Ni₅-Containing Heteropolytungstates [Ni₁₄(OH)₆(H₂O)₁₀(HPO₄)₄(P₂W₁₅O₅₆)₄]^34–and [Ni₅(OH)₄(H₂O)₄(β-GeW₉O₃₄)(β-GeW₈O₃₀(OH))]^13–

Abstract

The two Ni(2+)-containing heteropolytungstates [Ni14(OH)6(H2O)10(HPO4)4(P2W15O56)4](34-) (Ni14) and [Ni5(OH)4(H2O)4(β-GeW9O34)(β-GeW8O30(OH))](13-) (Ni5) have been successfully synthesized in aqueous, basic media under conventional reaction conditions, and they were characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric and elemental analyses, electrochemistry, and magnetic studies. The cyclic voltammetry (CV) patterns of Ni14 and Ni5 showed chemically reversible multielectronic waves for slow scan time scales. For Ni14, an important acidity inversion effect between its reduced forms was observed. Magnetic studies revealed dominant ferromagnetic interactions among the nickel(II) ions in both polyanions.