Wells–Dawson anion, a useful building block to construct one-dimensional chain as a chelate ligand coordinating with transition metal cations

Two composite compounds, [{Cu(PPD)2}(As2W18O60)]·2H2PPD·14H2O 1 (PPD = p-phenylenediamine) and [Cu4(Hen)2As2W18O68]·4H2en·18H2O 2 (en = ethylenediamine) have been prepared under mild hydrothermal conditions with difference in pH values of the initial reaction solutions and structurally characterized by single-crystal X-ray diffraction. Compound 1 exhibits a one-dimensional chain constructed from Wells–Dawson anions and Cu(II) coordination complex. It is the first example of a one-dimensional chain based on Wells–Dawson anions that act as chelate ligands to coordinate with transition metal. Compound 2 is constructed from trivacant Keggin polyanions linked through tetrameric copper unit, which coordinates with organonitrogen ligands.