Synthesis and Dehydrogenation of Organic Salts of a Five-Membered B/N Anionic Chain, a Novel Ionic Liquid

We have synthesized the tetrabutylammonium ([Bu₄ N]⁺ ), tetraethylammonium ([Et₄ N]⁺ ), guanidinium ([C(NH₂ )₃ ]⁺ ), and methylguanidinium ([C(N₃ H₅ CH₃ )]⁺ ) salts of the [BH₃ (NH₂ BH₂ )₂ H]^- anion, a five-membered B/N anionic chain, in high yields by the metathesis reactions of Na[BH₃ (NH₂ BH₂ )₂ H] with the corresponding halides and characterized them by NMR (¹¹ B, ¹¹ B{¹ H}, ¹ H, ¹ H{¹¹ B}, ¹³ C), IR, elemental analysis, TGA-DSC, and TGA-MS. These complexes behave like ionic liquids (ILs), in which the melting point of the [Bu₄ N][BH₃ (NH₂ BH₂ )₂ H] is the lowest (-51 °C). The dehydrogenation of these ILs have been studied through the thermal decomposition and catalytic hydrolysis in aqueous solution using the noble or non-noble metals or their salts as catalysts, and the results indicate that these ILs of five-membered B/N anionic chain are promising hydrogen storage materials.