Synthesis and characterization of noble-metal-substituted Dawson-type polyoxometalates

Polyoxometalates substituted by noble metal cations (PdII, RuIII, IrIV) of general formula (Bu4N)n[P2W17M(OH2)O61] are prepared by refilling the vacant site of the lacunary precursor α2-K10P2W17O61. Both 31P- and 183W-n.m.r. studies provide convincing evidence for the above structural assignment. The u.v.-vis and i.r. spectra are consistent with the first row transition metal substituted homologues. Electrochemical investigations by cyclic voltammetry in MeCN revealed four reversible one-electron redox couples, which are ascribed to the tungsten(VI→V) process of the tungsten-oxo framework.