A COMPARATIVE ELECTROCHEMICAL STUDY OF TRANSITION-METAL SUBSTITUTED DAWSON TYPE HETEROPOLYANIONS .1.

The comparative electrochemical behaviour, in aqueous solutions, of th e Dawson lacunary anion [P2W17O61](10-) and of the Fe-III Cu-II, Co-II , Ni-II, Mn-III and Mn-II substituted Dawson lacunary heteropolyanions is presented. The literature concerning the latter heteropolyanions h as been reviewed and completely new data are presented. The electroche mical behaviour observed for the reduction of the tungsten oxo centres , for all the heteropolyanions investigated, was found to be pH depend ent. Electrochemical evidence for the presence of the Fe-III, Cu-II, C o-II and the Mn-II and Mn-III cations in the ejected tungsten position was obtained with the N-II cation possessing no electroactivity.