Preparation and Characterization of Keggin Type Polyoxotungstates Containing Palladium or Iridium

Abstract The polyoxometalates substituted by noble metal cations (M = PdII or IrIV) with the formula (Bu4N)n[XW11M(OH2)O39] (X = B, n = 7; X = Si or Ge, n = 6; X = P, n = 5), were prepared by refilling the vacant site of the lacunary precursor KnXW11O39. 183W NMR studies provide convincing evidence for the above structural assignment. The UV-Vis and IR spectra are consistent with the first-row transition metal substituted homologues. The redox properties examined by cyclic voltammetry in acetonitrile exhibit two quasi-reversible, one-electron couples, which are ascribed to the W(VI→V) process of the tungsten-oxo framework.