|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1999 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Polyoxomolybdate complexes with the Anderson structure have been prepared so far by boiling a reaction mixture of Mo(VI) and heteroions at very high concentrations. However, the existence in solution remains to be confirmed. Our spectrophotometric studies have revealed that a series of Anderson complexes are formed and stable at very low concentrations of Mo(VI) and heteroions in aqueous solution, and the complex-formation reaction proceeds very rapidly even at room temperature. On the basis of these findings, a sensitive method was developed for the capillary electrophoretic determination of various oxoanions with 6-coordinated structures. Besides, the complex-formation reaction was applied to the oxidation-state analysis of Cr(III) and Cr(VI), and of I(V) and I(VII).
In aqueous-organic mixed media, we have found that Mo(VI) can react oxoanions with 3-coordinated structures including P(III), Se(IV) and Te(IV) to form 15-molybdo- and 12-molybd-complexes and crystallographic structure of the 12-molybdo-2-phosphonate complex has been determined. In addition, we have found that 12-tungstophosphate with the β-Keggin structure is stabilized by the presence of acetonitrile in the reaction mixture of Mo(VI) and P(V), being isolated as the tetraalkylammonium salt. It turned out that the new β-isomer underwent two-electron reductions in acidified organic media including acetone and acetonitrile. In aqueous-acetonitrile mixed media, the 12-molybdogallate complex with the Keggin structure was formed by the reaction of Mo(VI) and Ga(III), whereas the so-called Anderson complex was formed in aqueous solution. The formation of the Keggin complex was applied to the voltammetric determination of Ga(III).