Mixed-metal Dawson sandwich complexes:: Synthesis, spectroscopic characterization and electrochemical behaviour of Na16[MIICo3(H2O)2-(P2W15O56)2] (M = Mn, Co, Ni, Zn and Cd)

Mixed-metal Dawson sandwich complexes [MCo3(H2O)(2)-(P2W15O56)2](16-) (represented as {MCo3P4W30}) have been synthesized by the reaction of M2+, (where M = Mn, Co, Ni, Zn and Cd) with the "lacunary" sandwich complex alpha beta-[Na-Co-3(H2O)(2)(P2W15O56)(2)](17-) (represented as {NaCO3P4W30}): [NaCo3(H2O)(2)(P2W15O56)2](17-) + M2+-> [MCo3(H2O)(2)(P2W15-O-56)2](16-) + Na+. The {MCo3P4W30} species were characterized by IR spectroscopy, elemental analysis and P-31 solution NMR spectroscopy. The electrochemical behaviour of these mixed-metal sandwich complexes was investigated in aqueous solution and compared with that of beta beta[Co-4(H2O)(2)(P2W15O56)(2)](16-) (represented as beta beta-{Co4P4W30) and {NaCo3P4W30). (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007.