Electrochemistry of Isopoly and Heteropoly Oxometalates

<jats:title>Abstract</jats:title> <jats:p>The sections in this article are</jats:p> <jats:sec> <jats:title>Introduction</jats:title> <jats:sec> <jats:title>Definitions</jats:title> </jats:sec> <jats:sec> <jats:title>General Properties, Literature, and Topics Covered</jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> A simplified Overview of the Formation of <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title> Fundamental Redox Mechanisms of <jats:styled-content style="fixed-case">POMs</jats:styled-content> at Electrodes </jats:title> <jats:sec> <jats:title> Electrochemical Reductions of Selected Plenary <jats:styled-content style="fixed-case">POMs</jats:styled-content> : α‐[ <jats:styled-content style="fixed-case">Si</jats:styled-content> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>12</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>40</jats:sub> ] <jats:sup>4−</jats:sup> , α‐[ <jats:styled-content style="fixed-case">PW</jats:styled-content> <jats:sub>12</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>40</jats:sub> ] <jats:sup>3−</jats:sup> , α‐[ <jats:styled-content style="fixed-case">P</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>18</jats:sub> O <jats:sub>62</jats:sub> ] <jats:sup>6−</jats:sup> , and α‐[ <jats:styled-content style="fixed-case">H</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>12</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>40</jats:sub> ] <jats:sup>6−</jats:sup> </jats:title> <jats:sec> <jats:title>Aqueous Media</jats:title> </jats:sec> <jats:sec> <jats:title>Nonaqueous and Mixed Solvents</jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> Quinone/hydroquinone‐like Behaviors in the First Several Reduction Waves of <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> Selected Achievements that Illustrate the Basic Behaviors of Plenary <jats:styled-content style="fixed-case">POMs</jats:styled-content> at Electrodes </jats:title> <jats:sec> <jats:title> Heterogeneous One‐electron Exchange of α‐[ <jats:styled-content style="fixed-case">Si</jats:styled-content> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>12</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>40</jats:sub> ] <jats:sup>4−</jats:sup> in Dimethylformamide </jats:title> </jats:sec> <jats:sec> <jats:title>The Reduction Potential of the One‐electron Wave and the Role of the Central Heteroatom</jats:title> </jats:sec> <jats:sec> <jats:title>Isomerization upon Reduction</jats:title> </jats:sec> <jats:sec> <jats:title> <jats:styled-content style="fixed-case">POM</jats:styled-content> ‐solvent Interactions as Probed by the Redox Potentials of Two <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title> Structure of Electrolyte Solutions As Probed by the Electrochemical Behaviors of <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title>Cation and Pressure Effects on the Electrochemistry of 12‐Tungstocobaltate and 12‐Tungstophosphate Ions in Acidic Aqueous Solution</jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> Mixed Addenda and Other Substituted <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> <jats:sec> <jats:title> Comparison of Valence Trapping in Uniform and Mixed Addenda Plenary <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title> Lacunary and Transition Metal–substituted <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> <jats:sec> <jats:title> Lacunary <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title> Transition Metal–monosubstituted <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title> An Interesting Case of Mixing up of Substituent and Tungsten Waves: α <jats:sub>1</jats:sub> ‐ and α <jats:sub>2</jats:sub> ‐[ <jats:styled-content style="fixed-case">Fe</jats:styled-content> <jats:sup>III</jats:sup> ( <jats:styled-content style="fixed-case">OH</jats:styled-content> <jats:sub>2</jats:sub> ) <jats:styled-content style="fixed-case">P</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>17</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>61</jats:sub> ] <jats:sup>7−</jats:sup> </jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> Sandwich‐type <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> <jats:sec> <jats:title> Electron Transfer Behaviors of Multi‐iron Sandwich‐type <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> <jats:sec> <jats:title>Electrochemical Probing of Siderophoric Behavior in Sandwich‐type Multi‐iron Wells–Dawson Heteropolytungstates</jats:title> </jats:sec> </jats:sec> </jats:sec> <jats:sec> <jats:title>Recent Developments</jats:title> <jats:sec> <jats:title> Electrochemistry of a New Family of Wells–Dawson Anions: Semivacant Tungstophosphates and Arsenates [ <jats:styled-content style="fixed-case">H</jats:styled-content> <jats:sub>4</jats:sub> <jats:styled-content style="fixed-case">XW</jats:styled-content> <jats:sub>18</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>62</jats:sub> ] <jats:sup>7−</jats:sup> ( <jats:styled-content style="fixed-case">X</jats:styled-content>  =  <jats:styled-content style="fixed-case">P</jats:styled-content> or As) </jats:title> <jats:sec> <jats:title> Evidence for an Influence of the Dissymmetry on the Voltammetric Behavior of <jats:styled-content style="fixed-case">PW</jats:styled-content> <jats:sub>18</jats:sub> : Comparison with <jats:styled-content style="fixed-case">P</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>18</jats:sub> </jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title> Recent Achievements in Apparently Direct Multiple Electron Transfers on the First Waves of <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> <jats:sec> <jats:title> Electrochemistry of the Multi‐nickel Polyoxoanions [ <jats:styled-content style="fixed-case">Ni</jats:styled-content> <jats:sub>6</jats:sub> As <jats:sub>3</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>24</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>94</jats:sub> ( <jats:styled-content style="fixed-case">H</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> ) <jats:sub>2</jats:sub> ] <jats:sup>17−</jats:sup> , [ <jats:styled-content style="fixed-case">Ni</jats:styled-content> <jats:sub>3</jats:sub> <jats:styled-content style="fixed-case">Na</jats:styled-content> ( <jats:styled-content style="fixed-case">H</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> ) <jats:sub>2</jats:sub> ( <jats:styled-content style="fixed-case">As</jats:styled-content> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>9</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>34</jats:sub> ) <jats:sub>2</jats:sub> ] <jats:sup>11−</jats:sup> , and [ <jats:styled-content style="fixed-case">Ni</jats:styled-content> <jats:sub>4</jats:sub> <jats:styled-content style="fixed-case">Mn</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">P</jats:styled-content> <jats:sub>3</jats:sub> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>24</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>94</jats:sub> ( <jats:styled-content style="fixed-case">H</jats:styled-content> <jats:sub>2</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> ) <jats:sub>2</jats:sub> ] <jats:sup>17−</jats:sup> </jats:title> </jats:sec> <jats:sec> <jats:title> Electrochemistry of the Iron(III)‐substituted Keggin Dimer, [ <jats:styled-content style="fixed-case">Fe</jats:styled-content> <jats:sub>6</jats:sub> ( <jats:styled-content style="fixed-case">OH</jats:styled-content> ) <jats:sub>3</jats:sub> (A‐α‐ <jats:styled-content style="fixed-case">Ge</jats:styled-content> <jats:styled-content style="fixed-case">W</jats:styled-content> <jats:sub>9</jats:sub> <jats:styled-content style="fixed-case">O</jats:styled-content> <jats:sub>34</jats:sub> ( <jats:styled-content style="fixed-case">OH</jats:styled-content> ) <jats:sub>3</jats:sub> ) <jats:sub>2</jats:sub> ] <jats:sup>11−</jats:sup> </jats:title> </jats:sec> </jats:sec> <jats:sec> <jats:title>Theoretical Approaches</jats:title> <jats:sec> <jats:title> Electronic Structures of <jats:styled-content style="fixed-case">POMs</jats:styled-content> Explain their Redox Behaviors and the Relative Stability of Reduced Forms </jats:title> </jats:sec> <jats:sec> <jats:title> An Extended Hückel Calculations Approach to a Qualitative Understanding of the Initial Electron Transfer Site in Dawson‐type <jats:styled-content style="fixed-case">POMs</jats:styled-content> </jats:title> </jats:sec> </jats:sec> </jats:sec> <jats:sec> <jats:title>Electrocatalysis</jats:title> <jats:sec> <jats:title>Basic Concepts of Homogeneous Catalysis of Electrode Reactions</jats:title> </jats:sec> <jats:sec> <jats:title>Selected Electrocatalysis in Homogeneous Solution</jats:title> <jats:sec> <jats:title>Electrocatalytic Reductions</jats:title> </jats:sec> <jats:sec> <jats:title>Electrocatalytic Oxidations</jats:title> </jats:sec> </jats:sec> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> </jats:sec> <jats:sec> <jats:title>Acknowledgment</jats:title> </jats:sec>