Redox Reactions of Bismuth Subhalides, BiI and Bi₆Cl₇, in Acidic Room-temperature Chloroaluminate Melt

Abstract

Electrochemical study on redox reactions of polybismuth cations has been carried out in the acidic 1-metyl-3-benzyl imidazolium chloride (MeBzImCl) + 67 mol % AlCl₃ melt, where MeBzImCl was synthesized from 1-methyl imidazole and benzyl chloride. The reduction of Bi₄⁴⁺ to Bi₈²⁺ (Bi₄⁴⁺ + 3e = 1 / 2 Bi₈²⁺) occurs at the cathodic peak around 0.6 V for BiI dissolved into this melt. The number of electron which took part into reduction at the cathodic peak around 0.6 V was determined as 2.8 ± 0.3 by polarography for BiI. For Bi₆Cl₇ dissolved into this melt, the reductions of Bi³⁺ to Bi⁺, Bi₅³⁺ to Bi₈²⁺ and Bi₈²⁺ to Bi metal occur at the cathodic peaks around 0.9, 0.7 and 0.2 V, respectively. The oxidations of Bi₅³⁺ to Bi³⁺ and Bi₈²⁺ to Bi³⁺ occur at the anodic peaks around 1.45 and 1.67 V for both BiI and Bi₆Cl₇.