A new class of 30-molybdo complexes: Formation, structure and electrochemical properties of bisselenitopyrophosphatotriacontamolybdate, [(SeO3)2(P2O7)Mo30O90]8−, and bispyrophosphatotriacontamolybdate, [(P2O7)2Mo30O90]8−

The tetrapropylammonium (Pr4N+) salt of [(SeO3)2(P2O7)Mo30O90]8− was prepared from a 75 mM MoVI–2.8 mM P2O74−–5.6 mM SeO32−–0.95 M HCl–60% (v/v) CH3CN system, where [(P2O7)Mo18O54]4− and [H6(SeO3)2Mo15O48]4− are first formed, then being spontaneously fused into [(SeO3)2(P2O7)Mo30O90]8−. The [(SeO3)2(P2O7)Mo30O90]8− anion may be isotypic with [(HPO3)2(P2O7)Mo30O90]8−, in which each side of a (P2O7)Mo12O42 fragment is capped by a B-type (HPO3)Mo9O24 unit derived from [H6(HPO3)2Mo15O48]4−. [(XO3)2(P2O7)Mo30O90]8− (X = HP, Se) have the same type of 30-molybdo framework as [(P2O7)2Mo30O90]8−, previously isolated by Koltz. These three 30-molybdo complexes with the same ionic charge of −8 constitute a new class of polyoxometallates and have common properties of undergoing a two-electron reduction in the absence of H+.

Graphical abstractThe [(P2O7)2Mo30O90]8− (a) and [(XO3)2(P2O7)Mo30O90]8− (X = Se (b), HP(c)) complexes constitute a new class of POMs, and are electrochemically reduced by two-electrons in the absence of H+.Figure optionsDownload full-size imageDownload as PowerPoint slide