Salts of highly fluorinated weakly coordinating anions as versatile precursors towards hydrogen storage materials

Abstract

We report the most recent results related to application of a metathetic pathway towards mixed-metal borohydrides. The synthetic protocol utilizes highly-fluorinated weakly coordinating anion salts as precursors. We discuss the technicalities related to the use of fluorine-rich anions as well as the improvements which are still needed to deliver high-purity materials with potential applications for hydrogen storage. The applicability of the method is expanded beyond the previously described complex borohydrides of alkali metal Zn or Y, towards the systems containing Mg^II, Sc^III, Mn^II, or Eu^III. We have prepared for the first time [Ph₄P]₂[Mn(BH₄)₄] and [Me₄N]₂[Mg(BH₄)₄], solved their crystal structures from powder x-ray diffraction, and used selected organic metal borohydride derivatives as precursors towards mixed-metal borohydrides (K₂Mn(BH₄)₄, Rb₃Mg(BH₄)₅, etc.). We have also prepared [Ph₄P][Eu(BH₄)₄], which is the first derivative of Eu^III in the homoleptic environment of borohydride anions.