PREPARATION AND CHARACTERIZATION OF KEGGIN-TYPE POLYOXOTUNGSTATES CONTAINING PALLADIUM OR IRIDIUM

The polyoxometalates substituted by noble metal cations (M = Pd-II or Ir-IV) with the formula (BU4N)(n)[XW11M(OH2)O-39] (X = B, n = 7; X = S i or Ge, n = 6; X = P, n = 5), were prepared by refilling the vacant s ite of the lacunary precursor KnXW11O39. W-183 NMR studies provide con vincing evidence for the above structural assignment. The W-Vis and IR spectra are consistent with the first-row transition metal substitute d homologues. The redox properties examined by cyclic voltammetry in a cetonitrile exhibit two quasi-reversible, one-electron couples, which are ascribed to the W(VI-->V) process of the tungsten-oxo framework.