Nucleophilicity in ionic liquids. 2. Cation effects on halide nucleophilicity in a series of bis(trifluoromethylsulfonyl)imide ionic liquids

In this work, the nucleophilicities of chloride, bromide, and iodide have been determined in the ionic liquids [bmiml [N(Tf)(2)], [bM(2)iM] [N(Tf)(2)], and [bmpyl [N(Tf)21 (where bmim = 1-butyl-3-methylimidazolium, bM2iM = 1-butyl-2,3-dimethylimidazolium, bmpy = 1-butyl-1-methylpyrrolidinium, and N(Tf)(2) = bis(trifluoromethylsulfonyl)imide). It was found that in the [bmim](+) ionic liquid, chloride was the least nucleophilic halide, but that changing the cation of the ionic liquid affected the relative nucleophilicities of the halides. The activation parameters DeltaH(double dagger), DeltaS(double dagger), and DeltaG(double dagger) have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.