Syntheses, Solution Multi-NMR Characterization, and Reactivities of [C₆F₅Xe]⁺ Salts of Weakly Coordinating Borate Anions, [BY₄]^- (Y = CF₃, C₆F₅, CN, or OTeF₅)

New examples of [C₆F₅Xe]⁺ salts of the weakly coordinating anions [B(CF₃)₄]^-, [B(C₆F₅)₄]^-, [B(CN)₄]^-, and [B(OTeF₅)₄]^- have been synthesized by metathesis reactions of [C₆F₅Xe][BF₄] with the corresponding M^I[BY₄] salts (M^I = K or Cs; Y = CF₃, C₆F₅, CN, or OTeF₅). The salts were characterized in solution by multi-NMR spectroscopy. Their stabilities in prototypic solvents (CH₃CN and CH₂Cl₂) and decomposition products are reported. The influence of the coordinating nature of [BY₄]^- on the decomposition rate of [C₆F₅Xe]⁺ as well as the presence of the weakly nucleophilic [BF₄]^- ion has been studied. The electrophilic pentafluorophenylation of C₆H₅F by [C₆F₅Xe][BY₄] in solvents of different coordinating abilities (CH₃CN and CH₂Cl₂) and the effects of stronger nucleophiles (fluoride and water) on the pentafluorophenylation process have been investigated. Simulations of the ¹⁹F and ¹²⁹Xe NMR spectra of [C₆F₅Xe]⁺ have provided the complete set of aryl ¹⁹F−¹⁹F and ¹²⁹Xe−¹⁹F coupling constants and their relative signs. The ¹⁹F NMR parameters of the [C₆F₅Xe]⁺ cation in the present series of salts are shown to reflect the relative degrees of cation−solvent interactions.