Electrochemical studies on bis(β-diketonato)(dimethylsulfoxide)dioxouranium(VI) in dimethylsulfoxide

Electrochemical studies on (UO2)-O-VI(beta-diketonato)(2)dmso [beta-diketonate=dibenzoylmethanate (dbm), trifluoroacetylacetonate (tfacac), hexafluoroacetylacetonate (hfacac), dmso=dimethyl sulfoxide] complexes in DMSO containing tetrabutylammonium perchlorate (supporting electrolyte) have been carried out using cyclic voltammetry (CV) and normal pulse voltammetry (NPV). As a result, it was found that the (UO2)-O-VI(tfacac or hfacac),dmso complexes are reduced to U(V) species reversibly and that the (UO2)-O-VI(dbm)(2)dmso complex is quasi-reversibly reduced to U(V) species. The formal redox potentials (E degrees/V, vs. Ag/AgCl and vs. ferrocene/ferricinium in parentheses) for the U(VI)/U(V) couple are -0.44 (-0.97) for (UO2)-O-VI(hfacac)(2)dmso, -0.52 (-1.05) for (UO2)-O-VI(tfacac)(2)dmso, and -0.83 (-1.36) for (UO2)-O-VI(dbm)(2)dmso. Furthermore, the E degrees values were found to correlate with the pK(a), values of beta-diketones, i.e. the E degrees values decrease with an increase in the pK(a), value. (C) 1998 Elsevier Science S.A.