Abstract
The mechanisms of hydrogen release from methylamine with or without borane, alane, diborane, dialane, and borane–alane are theoretically explored. Geometries of stationary points are optimised at the MP2/aug-cc-pVDZ level and energy profiles are refined at the CCSD(T)/aug-cc-pVTZ level based on the second-order Møller–Plesset (MP2) optimised geometries. H2 elimination is impossible from the unimolecular CH3NH2 because of a high energy barrier. The results show that all catalysts can facilitate H2 loss from CH3NH2. However, borane or alane has no real catalytic effect because the H2 release is not preferred as compared with the B–N or Al–N bond cleavage once a corresponding adduct is formed. The diborane, dialane, and borane–alane will lead to a substantial reduction of energy barrier as a bifunctional catalyst. The similar and distinct points among various catalysts are compared. Hydrogen bond and six-membered ring formation are two crucial factors to decrease the energy barriers.
Acknowledgements
We thank the Beijing Key Laboratory of Ionic Liquids Clean Process and State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences for providing computational resources.
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