Dihydrogen generation from amine/boranes: synthesis, FT-ICR, and computational studies

Area of Science:

• Inorganic Chemistry
• Physical Chemistry
• Materials Science

Background:

• Amine/boranes are compounds with potential applications in hydrogen storage.
• Understanding their reaction mechanisms is crucial for optimizing hydrogen generation.

Purpose of the Study:

• To investigate the gas-phase protonation of ammonia-borane and various amine/boranes.
• To determine the structural effects on the energetic thresholds for dihydrogen formation.
• To elucidate the reaction mechanism and identify stable intermediates and products.

Main Methods:

• Fourier transform ion cyclotron resonance spectrometry (FT-ICR) was employed for gas-phase studies.
• Isotopic substitution was used to ascertain the reaction mechanism.
• Computational analyses (MP2/6-311+G(d,p)) were performed to assess thermodynamic stabilities and acidities.

Main Results:

• Protonation of all studied amine/boranes exclusively yielded dihydrogen (H2).
• The primary intermediate and final species were identified as R(1)R(2)R(3)N-BH(4)(+) and R(1)R(2)R(3)N-BH(2)(+), respectively.
• The R(1)R(2)R(3)N-BH(4)(+) ions feature a unique three-center, two-electron bond involving a loosely bound H2 molecule.

Conclusions:

• The study provides insights into the mechanism of dihydrogen generation from amine/boranes.
• Identified key structural features and intermediates relevant for hydrogen storage applications.
• A foundation for designing amine/borane compounds optimized for efficient dihydrogen release and storage.