Abstract
By employing elemental analysis, 31P NMR, pH, and conductivity measurements, the protonated state of lacunary heteropolyoxotungstophosphates in aqueous solution, {PW11O39}, is determined to be [H3PW11O39]4−. Using it as ligand, a complex of [Ag(H2O)(H3PW11O39)]3− is formed. An electrochemical cell is designed as follows: (−) Hg, Hg2Cl2 [Ag(H2O)(H3PW11O39)]3− (aq) | Ag(s) (+) (salt bridge is saturated KNO3 solution). By measuring the electromotive force of the cell, the stability constant of [Ag(H2O)(H3PW11O39)]3− in aqueous solution is determined to be 4.34 × 103 (25 °C).