[Ar(Ar′)I][N(CF3)2], effect of fluorine substituents on aryl groups of iodonium cations and of coordinating bases on the fluoride transfer from the anion to the cation

Three prototypical fluoroaryliodonium salts with the [N(CF3)2]− anion were obtained by metathesis in the corresponding tetrafluoroborate salts [Ar(Ar′)I][BF4] (Ar/Ar′ = C6H5/4-FC6H4, 3-FC6H4/4-FC6H4, C6F5/C6F5) with in situ generated Rb[N(CF3)2]. The kinetic lability of the [N(CF3)2]− anion (potential fluoride donor like [OCF3]−) in combination with the gradual change in fluoride affinity of the three [Ar(Ar′)I]+ fluoroaryliodonium cations allowed to distinguish the fluoride acceptor property of the three [Ar(Ar′)I]+ fluoroaryliodonium cations. Coordinating solvents or ligands suppressed the fluoride transfer from the [N(CF3)2]− anion to the fluoroaryliodonium cation.

Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of [Ar(Ar′)I][N(CF3)2] salts in CH3CN by anion metathesis.
► [Ar(Ar′)I][N(CF3)2] salts are stabilized by the coordinating solvent CH3CN or a stronger N-base.
► Removal of the stabilizing N-base is accompanied by fluoride transfer from the anion to the cation.
► Ar(Ar′)IF is an efficient fluoride donor and forms [N(CF3)2]− when reacted with CF3SO2N(CF3)2.