Full paper / Mémoire Synthesis, structural characterization, and electrocatalytic studies of abba-(Zn II OH 2 ) 2 (Fe III ) 2 (X 2 W 15 O 56 ) 2 14- (X = P or As)

The synthesis and characterization of the previously unknown mixed-metal sandwich-type Wells–Dawson complexes, abba[(Zn II OH2)2(Fe III )2(P2W15O56)2] 14– (Zn2Fe2P4) and abba-[(Zn II OH2)2(Fe III )2(As2W15O56)2] 14– (Zn2Fe2As4), are described. The complexes are prepared by the reaction of Zn(II) with the divacant lacunary species, aaaa-[(NaOH2)2(Fe III )2(P2W15O56)2] 16– and aaaa-[(NaOH2)2(Fe III )2(As2W15O56)2] 16– , respectively, and are characterized by X-ray crystallography, infrared and NMR spectroscopy, elemental and thermogravimetric analyses, differential scanning calorimetry, and cyclic voltammetry. Like their analogues, abba-[(Mn II OH2)2(Fe III )2(P2W15O56)2] 14– (Mn2Fe2P4) and abba-[(Mn II OH2)2(Fe III )2(As2W15O56)2] 14– (Mn2Fe2As4), the remarkable stability observed for these complexes from pH 0 to at least 6 has permitted a comprehensive evaluation of their electrocatalytic abilities toward the reduction of O2 ,H 2O2 ,H NO2 and NO. A comparison of the properties of the mixed-metal Zn(II) and Mn(II) complexes is provided. To cite this article: I.M. Mbomekalle et al., C. R. Chimie 8 (2005).