Electrochemical and Spectroscopic Study of Ce(III) Coordination in the 1-Butyl-3-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquid Containing Chloride Ion

Abstract

Cyclic staircase voltammetry, controlled potential coulometry, and electronic absorption spectroscopy were used to probe the coordination and accessible oxidation states of Ce(3+) dissolved in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyroTf(2)N) before and after the addition of chloride ion as BuMePyroCl. Controlled potential coulometry indicated that the oxidation of Ce metal in this ionic liquid produces only Ce(3+). Spectroscopic examination of the resulting solutions indicated that Ce(3+) was weakly solvated by Tf(2)N(-) ions as [Ce(Tf(2)N)(x)]((x-3)-), x ≥ 3. This species can be reduced at negative potentials, probably to a related Ce(2+) species, but the latter is unstable and quickly disproportionates to Ce(3+) and Ce(0); the latter appears to react with the ionic liquid. The addition of Cl(-) to solutions of [Ce(Tf(2)N)(x)]((x-3)-) causes the precipitation of CeCl(3)(s), providing a convenient route to the nondestructive recovery of Ce(3+) from the ionic liquid. However, as the Cl(-) concentration is further increased, the CeCl(3)(s) redissolves as the octahedral complex, [CeCl(6)](3-), and the voltammetric and spectroscopic signature for [Ce(Tf(2)N)(x)]((x-3)-) disappears. Absorption spectroscopy indicated that the bulk controlled potential oxidation of solutions containing [CeCl(6)](3-) produces [CeCl(6)](2-). Although stable on the time scale of voltammetry, this species slowly reacts with the ionic liquid and is converted back to [CeCl(6)](3-).

Electrochemical and Spectroscopic Study of EuIII and EuII Coordination in the 1‐Ethyl‐3‐methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid

“…[11] In contrast,I Lw ere shownt ob eg ood solvents for the stabilization and study of the oxidation states + II and + IV for Ln. [12][13][14][15] Specifically,E u II can be stabilized in aqueous solutions thanks to cyclic ligands such as cryptands or analogues [16] whereasi nn onaqueousm edia, fully dissolved stablef orms of Ln II can be observed. [17,18] The electrochemical behavior of the Eu III /Eu II redoxc ouple was extensively studiedi nawide range of IL [14,[19][20][21][22][23][24][25][26][27] and its apparent standard potential was found to vary between0and À1.0 Vv ersus ferrocenium/ferrocene (Fc + /Fc) reference, depending on the medium.…”

Electrodeposition of Pt and Gd from the Same Ionic Liquid

“…A number of reports have addressed the electrochemical deposition of rare earth metals from ionic liquids (29)(30)(31)(32)(33)(34)(35). The electrodeposition of RE metal from RE 3+ ions is often not a single step process but involves the intermediate formation of a lower valency species (36)(37)(38) which is stable for some RE/IL combinations, and disproportionates to metal and RE 3+ for others (36)(37)(38)(39). Especially in butylmethylpyrrolidinium bistrifluoromethylsulfonylimide (BMP TFSI), surface passivation instead of metal deposition was observed for a number of RE metals, like Ce, Pr and Nd (36,37).…”

“…The electrodeposition of RE metal from RE 3+ ions is often not a single step process but involves the intermediate formation of a lower valency species (36)(37)(38) which is stable for some RE/IL combinations, and disproportionates to metal and RE 3+ for others (36)(37)(38)(39). Especially in butylmethylpyrrolidinium bistrifluoromethylsulfonylimide (BMP TFSI), surface passivation instead of metal deposition was observed for a number of RE metals, like Ce, Pr and Nd (36,37). Many studies on RE metal deposition were characterized by the absence of a corresponding dissolution peak (30,33,34,40), which is explained by slow charge transfer kinetics or reactions with residual moisture (33) or the ionic liquid (34).…”

A comparative study of the cathodic behaviour of EuCl3 in two imidazolium chloride ionic liquids, the 1-butyl-3-methylimidazolium (C4mimCl) and the 1-ethyl-3-methylimidazolium (C2mimCl), on a glassy carbon electrode

“…By contrast, the electrochemistry of Cerium (III) has been studied in the basic AlCl 3 -1-methyl-3-ethylimidazolium chloride [21] and in 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide containing chloride ions [2], in both cases, it is reported that Ce(III) (i.e. CeCl 6 3 − ) is oxidized to Ce(IV) (i.e.…”