The oxidative electrochemistry of [CpFe(CO)(2)](2), 1 (CP = [eta(5)-C5H5](-)), was examined in detail in ionic liquids (ILs) composed of ions of widely varying Lewis acid-base properties. Cyclic voltammetric responses were strongly dependent on the nucleophilic properties of the IL anion, but all observations are consistent with the initial formation of 1(+) followed by attack from the IL anion. In [NTf2](-)-based ILs ([NTf2](-)=bis(trifluoromethylsulfonyl)amide), the process shows nearly ideal chemical reversibility as the reaction between 1(+) and [NTf2] is very slow. This is highly significant, as 1(+) is known to be highly susceptible to nucleophilic attack and its stability indicates a remarkable lack of coordinating ability of these ILs. In 1-methyl-3-butylimidazolium hexafluorophosphate, [bmim][PF6], the oxidation of 1 is still largely reversible, but there is more pronounced evidence of [PF6](-) coordination. In contrast, 1 exhibits an irreversible two-electron oxidation process in a dicyanamide-based IL.