Dehydrogenation of ammonia borane in fluoro alcohols

Abstract

Dehydrogenation of ammonia borane was carried out in fluoro alcohol solvent in order to obtain compounds that are more likely candidates suitable for regeneration. Even though ammonia borane undergoes self-dissociation in 2,2,2-trifluoroethanol to liberate H₂, decent hydrogen release rates were obtained by using Co–Co₂B, Ni–Ni₃B, and Co–Ni–B nanocomposites as catalysts. These catalysts are magnetic in nature and hence can be separated from the reaction mixture using a magnet for re-use. The final by-product NH₄⁺ B(OCH₂CF₃)₄⁻ obtained after the catalytic dehydrogenation of ammonia borane was thoroughly characterized using ¹H, ¹¹B, and ¹³C NMR and IR spectroscopies. The FTIR data showed that the B–O bond in NH₄⁺ B(OCH₂CF₃)₄⁻ is slightly weaker compared to boric acid. Preliminary investigations on the regenerative routes for ammonia borane from the by-product NH₄⁺ B(OCH₂CF₃)₄⁻ showed indications of the formation of BNH_x species.