Iron(III) and titanium(IV) appear to be complexed as [FeBr4]− and [TiBr6]2-, respectively, in the Lewis basic AlBr3-1-methyl-3-ethylimidazolium bromide (AlBr3-MeEtimBr) ionic liquid. Both species exhibit one electron reversible reduction at a glassy carbon electrode with voltammetric half-wave potentials of ca. −0.09 and −0.30V, respectively, vs. Al in the 66.7/33.3 mole percent AlBr3-MeEtimBr ionic liquid. The half-wave potentials for both the [FeBr4]−/2' and [TiBr6]2−/3- systems are very close to values that were measured for the corresponding chloride redox systems in the AlCl3-MeEtimCl ionic liquid. The Stokes-Einstein products for [FeBr4]− and [TiBr6]2- are 4.1 × 10–10 and 2.0 × 10−10 g cm s−2 K−1 respectively, and are in good agreement with literature values for the corresponding chloride complexes. The introduction of oxide ion into solutions containing [TiBr6]2- by dissolution of Li2CO3 appears to produce an oxide bromide complex, possibly [TiOBr4]2-, with a voltammetric reduction peak potential of approximately −0.56V, but titanium (IV) appears to react very slowly with oxide that is already present in the melt.
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