Actinides in Solution: Complexation and Kinetics

Comparative Study of f-Element Electronic Structure across a Series of Multimetallic Actinide and Lanthanoid-Actinide Complexes Possessing Redox-Active Bridging Ligands

“…Coordination of additional lanthanide or uranium metallocene moieties to the tpy sites of 5a-b was expected to introduce additional redox activity in these complexes, particularly in light of the voltammetry of (C 5 Me 5 ) 2 Yb(tpy) (11), which exhibits a tpy-based oxidation and a Yb-based reduction wave ( Figure 5). In fact, our initial report on the mixed-metal Yb III -Th IV -Yb III and Yb III -U IV -Yb III complexes 6a-b demonstrated a larger than expected number of redox events present in the compounds, 25 observations which were sample independent thereby alleviating concerns over sample purity.…”

“…For example, actinyl "cation-cation" complexes, resulting from metal···oxo [O=An=O] n+ ···AnO 2 interactions, are considered important in this context. [9][10][11] A few examples of mixed-valent uranium complexes have appeared in the literature and include the uranium bimetallic systems [N{CH 2 CH 2 N(Si t BuMe 2 )} 3 U] 2 (μ-Cl) (1), 12 U 2 (O t Bu) 9 (2), 13 and [K(18-crown-6)(Et 2 O)][UO{µ 2 -NCH 2 CH 2 N(CH 2 CH 2 N(Si t BuMe 2 )) 2 }] 2 (3), 14 which reportedly exhibit canonical U III /U IV , U IV /U V , and U V /U VI valences, respectively (Chart 1). The chloride ligand of complex 1 resides on a crystallographic inversion center with a U-Cl distance uranium(IV)-chloride distances; the complex was assigned as a species with intermediate uranium valencies.…”

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO3, and Na2CO3 solutions

“…These oxidation states are prone to change via oxidation and disproportionation reactions depending on the proton and oxygen concentration [1]. The ions in the aqueous solution behave as strong Lewis acids, and the ions with oxidation states that are higher than pentavalent form di-or tri-oxo ions.…”

Challenging conventional f-element separation chemistry – reversing uranyl(vi)/lanthanide(iii) solvent extraction selectivity

“…[20] However, there is also evidence that, under comparable reaction conditions, uranyl(VI) will more readily coordinate to such ligand sets than Ln(III). [21] Taken in conjunction with the observation that U(VI) tends to form more stable complexes in solution than Ln(III), [22] and our preliminary spectroscopic studies indicating that U(VI) more readily coordinates to H2salen-SO3 than Nd(III) or Eu(III), [23] it would appear that H2salen-SO3 could be applied to f-element separation chemistry.…”