Effect of complexing agents on the disproportionation of uranium (V)

Mehta, Mihir; Saraiya, S.C.; Sundaram, A. K.

doi:10.1007/bf03049072

Cited by 2 publications

(5 citation statements)

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“…Therefore, the outer-sphere electron transfer as suggested by Kern–Orlemann is highly likely when the uranyl(V) is complexed with anionic ligands. In fact, the favorability of protonation reaction of uranyl(V) is in perfect agreement with the rate of increase of disproportionation for the anionic ligands. , …”

Section: Resultsmentioning

confidence: 55%

“…Therefore, similar kind of hydrolysis reactions can also be anticipated for uranyl(V) . The disproportionation of uranyl(V) complexed with a range of anionic ligands were explored in aqueous solutions and the anionic ligands were found to increase the rate of disproportionation. , …”

Section: Introductionmentioning

confidence: 94%

“…29 The disproportionation of uranyl(V) complexed with a range of anionic ligands were explored in aqueous solutions and the anionic ligands were found to increase the rate of disproportionation. 17,18 The effect of H + concentration on the uranyl(V) disproportionation rate was examined through kinetic isotopic effects and the ratio for the rates determined in H 2 O and D 2 O is k D /k H = 1.7 and this suggests that the proton transfer mechanism is unlikely. However, the electron transfer process may happen in the presence of H + as suggested by Duke and Pinkerton.…”

Section: [ ] + [ ] → [ ] + [ ]mentioning

confidence: 99%

“…In fact, the favorability of protonation reaction of uranyl(V) is in perfect agreement with the rate of increase of disproportionation for the anionic ligands. 17,18 Whilst going across the series of complexes from U1(aqua) to U2(chloro) to U3 (acetate) to U4(carbonate) complexes, the net charge present on these complexes are +1, 3-, 2-, and 5-, respectively. For the U2 and U3 complexes, the protonation energetics appear to be fairly close to each other.…”

Section: Model-iiimentioning

confidence: 99%

“…The uranyl [UO 2 ] 2+ ion, has been experimentally characterized as a stable linear oxo-cation, can form numerous coordination complexes with inorganic and organic multidentate ligands − and a range of theoretical studies have also been reported. − However, uranyl(V) ([UO 2 ] + ) ions are unstable and instantaneously undergo disproportionation in aqueous solutions. − An overall disproportionation reaction of uranyl(V) in aqueous solution is given below. …”

Section: Introductionmentioning

confidence: 99%

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Disproportionation of the Uranyl(V) Coordination Complexes in Aqueous Solution through Outer-Sphere Electron Transfer

Arumugam

Burton

2021

Inorg. Chem.

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Among the linear actinyl(VI/V) cations, the uranyl(V) species are particularly intriguing because they are unstable and exhibit a unique behavior to undergo H+ promoted disproportionation in aqueous solution and form stable uranyl(VI) and U(IV) complexes. This study uses density functional theory (DFT) combined with the conductor-like polarizable continuum model approach to investigate [UO2]2+/+ to [UIVO2] reduction free energies (RFEs) and explores the stability of uranyl(V) complexes in aqueous solution through computing disproportionation free energies (DFEs) for an outer-sphere electron transfer process. In addition to the aqua complex (U1), another three commonly encountered ligands such as chloride (U2), acetate (U3), and carbonate (U4) in aqueous environmental conditions are taken into account. For the U1 complex, the computed 1e– (V/IV) and 2e– (VI/IV) RFEs are in good agreement with experiments. The computed DFEs reveal that the presence of H+ is imperative for the disproportionation to take place. Although the presence of the alkali cations favors the disproportionation to some extent, they cannot fully make the reaction thermodynamically feasible. For the anionic complexes, the high negative charge does not allow for the formation of a cation–cation encounter complex due to Coulombic repulsion. Furthermore, an additional factor is the ligand exchange reaction which is also an energy-demanding step. Therefore, the current study examined the Kern–Orlemann mechanism and our results validate the mechanism based on DFT computed DFEs and propose that for the anionic complexes, an outer-sphere electron transfer is highly probable and our computed protonation free energies further support this claim.

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Section: Resultsmentioning

confidence: 55%