Abstract
A new structural family of heteropolytungstate complexes containing trans-dioxo uranium(VI) (uranyl) groups has been isolated in good yield by reaction of UO22+ with [NaAs4W40O140]27− (W40) in aqueous solution. The “lacunary” anion, [(UO2)3(H2O)5As3W29O104]19−1 is formed by the reaction of W40 with UO2(MeCO2)2 at pH 7, and the crystal structure of (NH4)19[(UO2)3(H2O)5As3W29O104]·28H2O [orthorhombic, P212121, a = 17.5626(2), b = 24.4929(2), c = 33.3019(3) Å] is reported. The “plenary” anion, [(UO2)3(H2O)6As3W30O105]15−2 is formed by reaction of W40 with UO2(NO3)2 at pH 4, and the crystal structure of (NH4)15[(UO2)3(H2O)6As3W30O105]·20H2O [monoclinic, P21/c, a = 23.63520(10), b = 18.0646(2), c = 35.32640(10) Å, β = 107.46°] is reported. Both heteropolyanions contain three B-AsW9O339− groups linked by uranyl cations (pentagonal bipyramids) and three (or two) additional corner-sharing WO6 octahedra cap the structure of 2 (1). A six-line 183W NMR spectrum of 2 is consistent with an effective C3v symmetry for the anion in solution. Addition of VO2+ to a solution of 1 yields the V-substituted anion (3) confirmed by a structure determination of (NH4)17[(UO2)3(H2O)6As3W29VIVO105]·44H2O [orthorhombic, Pnma, a = 31.1821(4), b = 24.9672(3) Å, c = 20.3460(3) Å]. The cyclic voltammogram of 3 in 0.5 M sodium acetate buffer (pH 4.7) shows the VIV/V couple at +0.26 V (Epc) and +0.40 V (Epa).
Published Version
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