Synthesis, crystal structure and catalytic activity of the guanidinium cation directed nickel(ii)-containing open Wells–Dawson 19-tungstodiarsenate(iii) [{Ni(H2O)4}2{Na(H2O)}As2W19O67(H2O)]9−

Abstract

A new example of an open Wells–Dawson type 19-tungstodiarsenate(III) [{Ni(H₂O)₄}₂{Na(H₂O)}As₂W₁₉O₆₇(H₂O)]⁹⁻ polyanion 1 has been synthesized in a single step reaction protocol, on the interaction of nickel chloride with the sodium salt of the trilacunary [B-α-AsW₉O₃₃]⁹⁻ ligand in aqueous solution (pH ∼ 5.8), in the presence of pyridine-2,6-dicarboxylic acid. The guanidinium cation plays a structure-directing role to crystallize polyanion 1 as a mixed salt of sodium and guanidinium salt in the triclinic space group P. The solid state structure shows an open Wells–Dawson type [As₂W₁₉O₆₇(H₂O)]¹⁴⁻ anion containing two nickel atoms in octahedral geometry. The mixed sodium and guanidinium salt of polyanion 1 was further characterized by FT-IR, single crystal X-ray diffraction, thermogravimetric analysis, and vibrating sample magnetometry (VSM). Polyanion 1a was screened as a catalyst for the oxidation of styrene.