[Sb(C6F5)4][B(C6F5)4]: An Air Stable, Lewis Acidic Stibonium Salt That Activates Strong Element-Fluorine Bonds
2014
As part of our ongoing interest in main group Lewis acids for fluoride anion complexation and element-fluorine bond activation, we have synthesized the stibonium borate salt [Sb(C₆F₅)₄][B(C₆F₅)₄] (3). The perfluorinated stibonium cation [Sb(C₆F₅)₄]⁺ present in this salt is a potent Lewis acid which abstracts a fluoride anion from [SbF₆]⁻ and [BF(C₆F₅)₃]⁻ indicating that it is a stronger Lewis acid than SbF₅ and B(C₆F₅)₃. The unusual Lewis acidic properties of 3 are further reflected by its ability to polymerize THF or to promote the hydrodefluorination of fluoroalkanes in the presence of Et₃SiH. While highly reactive in solution, 3 is a perfectly air stable salt, making it a convenient Lewis acidic reagent.
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