The pentafluoroethyltrihydridoborate anion: from shock sensitive salts to stable room temperature ionic liquids

Abstract

The reaction of pentafluoroethyllithium with BH₃·thf yields [C₂F₅BH₃]⁻ that is stable against H₂O, OH⁻ and air due to the electron withdrawing C₂F₅ group. M[C₂F₅BH₃] (M = K, Cs) are shock sensitive solids whereas salts with organic cations such as the room temperature ionic liquid [EMIm][C₂F₅BH₃] are stable for years. [C₂F₅BH₃]⁻ is a mild reducing agent, which is also reflected by its electrochemical properties. Oxidation with I₂ or Br₂ in the presence of Lewis bases yields the first stable adducts C₂F₅BH₂·L.