Molecular Mechanism for H₂ Release from BH₃NH₃, Including the Catalytic Role of the Lewis Acid BH₃
Journal Article
·
· Journal of Physical Chemistry A, 111(4):679-690
Electronic structure calculations using various methods, up to the coupled-cluster CCSD(T) level, in conjunction with the aug-cc-pVnZ basis sets with n ) D, T, and Q, extrapolated to the complete basis set limit, show that the borane molecule (BH₃) can act as an efficient bifunctional acid-base catalyst in the H₂ elimination reactions of XHnYHn systems (X, Y ) C, B, N). Such a catalyst is needed as the generation of H₂ from isoelectronic ethane and borane amine compounds proceeds with an energy barrier much higher than that of the X-Y bond energy. The asymptotic energy barrier for H₂ release is reduced from 36.4 kcal/mol in BH₃NH₃ to 6.0 kcal/mol with the presence of BH₃ relative to the molecular asymptote. The NH₃ molecule can also participate in a similar catalytic process but induces a smaller reduction of the energy barrier. The kinetics of these processes was analyzed by both transition-state and RRKM theory. The catalytic effect of BH₃ has also been probed by an analysis of the electronic densities of the transition structures using the atom-in-molecule (AIM) and electron localization function (ELF) approaches.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 921395
- Journal Information:
- Journal of Physical Chemistry A, 111(4):679-690, Journal Name: Journal of Physical Chemistry A, 111(4):679-690 Journal Issue: 4 Vol. 111
- Country of Publication:
- United States
- Language:
- English
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