Metal ion complexes derived from the alpha(1) isomer of (P2W17O61)(10-): comparison with the corresponding alpha(1) species

The lacunary alpha(1)- and alpha(2)-[P2W17O61](10-) isomers derived from th e Dawson molecule [alpha P2W18O62](10-) have been used as ligands for the f ollowing metal cations: Ca-II V-V, Mn-II, Fe-III, Co-II, Ni-II, Cu-II, Zn-I I, and Mo-VI, respectively. We have succeeded in obtaining pure samples of stable compounds of the sc, series. The cyclic voltammograms of these lacun ary precursor species as well as those of the substituted complexes have be en run in a pH 3 medium with the aim of finding out distinctive features fr om one series to the nest. Several compounds of the alpha(2) series are kno wn to be stable and can, therefore, serve eventually as references to disti nguish the two series. For the alpha(2) compounds, the first two two-electr on processes are followed by a set of two, presumably one-electron steps. a nd this fingerprint is observed throughout the series, except for the coppe r and the molybdenum derivatives. These last two complexes can, however, be identified by other specific features. As another general observation on s hifting from the sc, to the a, series, it is found also that the peak poten tial of the first tungsten wave is driven in the negative direction. Finall y, a simple rationale is offered for the whole set of observations. (C) 199 9 Elsevier Science S.A. All rights reserved.