Synthesis and structural characterization of new tungsten(VI) complexes with polycarboxylate ligands

The reactions of (NH4)2WS4 and three polycarboxylate ligands (including nitrilotriacetate (nta3−), citrate (Hcit3−) and ethylenediaminetetraacetate (EDTA4−)) in H2O/EtOH at ambient temperature have resulted in three new trioxotungsten (VI) complexes, K3[WO3(nta)]·H2O 1, (NH4)4[WO3(cit)]·2 H2O 2 and K2(NH4)2[W2O6(EDTA)]·4H2O 3, respectively. These three complexes have been characterized by IR, XPS, TGA–DTA, 1H and 13C NMR spectroscopy. And their structures have been determined by X-ray crystallographic studies, which confirm that 1 and 2 are mononuclear compounds and 3 is a binuclear compound. Each tungsten atom in 1–3 is coordinated to three unshared oxygen atoms, which adopt fac stereochemistry, while the remaining fac positions are occupied by three atoms from the ligands. The electrochemical properties of 2 and 3 have been investigated.