Metal ion complexes derived from the α1 isomer of (P2W17O61)10-:: comparison with the corresponding α1 species

The lacunary alpha(1)- and alpha(2)-[P2W17O61](10-) isomers derived from the Dawson molecule [alpha P2W18O62](10-) have been used as ligands for the following metal cations: Ca-II V-V, Mn-II, Fe-III, Co-II, Ni-II, Cu-II, Zn-II, and Mo-VI, respectively. We have succeeded in obtaining pure samples of stable compounds of the sc, series. The cyclic voltammograms of these lacunary precursor species as well as those of the substituted complexes have been run in a pH 3 medium with the aim of finding out distinctive features from one series to the nest. Several compounds of the alpha(2) series are known to be stable and can, therefore, serve eventually as references to distinguish the two series. For the alpha(2) compounds, the first two two-electron processes are followed by a set of two, presumably one-electron steps. and this fingerprint is observed throughout the series, except for the copper and the molybdenum derivatives. These last two complexes can, however, be identified by other specific features. As another general observation on shifting from the sc, to the a, series, it is found also that the peak potential of the first tungsten wave is driven in the negative direction. Finally, a simple rationale is offered for the whole set of observations. (C) 1999 Elsevier Science S.A. All rights reserved.