| ItisreportedthatthecomplexesofAg+/Co2+andlacunaryKeggin polyoxotungstophosphates have exhibited excellent activity in homogeneous catalytic water oxidation into O2.However,their stability was concerned by people.Based on this,firstly,potassium 11-tungstophosphate was prepared according to the reference,then the pure sample of K4[H3PW11O39]·14H2O was obtained by recryllization.By employing elemental analysis,31P NMR,pH value measurement and conductivity measurement,the protonated state of lacunary heteropolyoxotungstophosphates in aqueous solution is determined to be[H3PW11O39]4-.Usingitasligand,astabilityconstantoftwocomplexes([Ag?H2O?(H3PW11O39)]3-and[Co?H2O?(H3PW11O39)]2-)is determined.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?e.m.f.?of the cell,the stability constant of[Ag?H2O?(H3PW11O39)]3-in aqueous solution is determined to be3.43×103?25 oC?.And it is determined that the stability constant of Na2H3PW11O39Co?H2O?in aqueous solution is 5.13×104?25 oC?by equimolar coefficients of spectrophotometry.This is the first example of the stability constant of metal ion complexes based polyoxomelate ligands so far.Explore the determination stability constant of[Co4?H2O?2(PW9O34)2]10-by using spectrophotometry,the experiment shows that this method is not feasible. |
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