Chromium(III) chloride is complexed as [CrCl6]3- in the basic aluminum chloride-1-methyl-3-ethylimidazolium chloride melt, and it can be reduced to a Cr(II) species at a glassy carbon electrode. Absorption spectroscopy and titration experiments suggest that the Cr(II) is complexed as [CrCl4]2-. The Cr(III)/Cr(II) electrode reaction exhibits slow charge-transfer kinetics with a standard heterogeneous rate constant of 3.27 × 10-6 cm s-1 and a cathodic transfer coefficient of ca. 0.38 in the 44.4/55.6 mole percent (m/o) melt at 27°C. The formal electrode potential of the Cr(III)/Cr(II) chloride redox couple is -0.649 V in the 44.4/55.6 m/o melt. The Stokes-Einstein products of [CrCl6]3- and [CrCl4]2 complexes are 1.2 × 10-10 and 1.7 × 10-10 g cm s-2 K-1, respectively.
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