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J. M. D. Macelroy – One of the best experts on this subject based on the ideXlab platform.

  • Towards the design of novel boron- and nitrogen-substituted Ammonia-borane and bifunctional arene ruthenium catalysts for hydrogen storage
    Journal of computational chemistry, 2014
    Co-Authors: Sateesh Bandaru, Niall J. English, Andrew D. Phillips, J. M. D. Macelroy

    Abstract:

    Electronic-structure density functional theory calculations have been performed to construct the potential energy surface for H2 release from Ammonia-borane, with a novel bifunctional cationic ruthenium catalyst based on the sterically bulky β-diketiminato ligand (Schreiber et al., ACS Catal. 2012, 2, 2505). The focus is on identifying both a suitable substitution pattern for Ammonia-borane optimized for chemical hydrogen storage and allowing for low-energy dehydrogenation. The interaction of Ammonia-borane, and related substituted AmmoniaBoranes, with a bifunctional η6-arene ruthenium catalyst and associated variants is investigated for dehydrogenation. Interestingly, in a number of cases, hydride-proton transfer from the substituted Ammonia-borane to the catalyst undergoes a barrier-less process in the gas phase, with rapid formation of hydrogenated catalyst in the gas phase. Amongst the catalysts considered, N,N-difluoro Ammonia-borane and N-phenyl Ammonia-borane systems resulted in negative activation energy barriers. However, these types of AmmoniaBoranes are inherently thermodynamically unstable and undergo barrierless decay in the gas phase. Apart from N,N-difluoro Ammonia-borane, the interaction between different types of catalyst and Ammonia borane was modeled in the solvent phase, revealing free-energy barriers slightly higher than those in the gas phase. Amongst the various potential candidate Ru-complexes screened, few are found to differ in terms of efficiency for the dehydrogenation (rate-limiting) step. To model dehydrogenation more accurately, a selection of explicit protic solvent molecules was considered, with the goal of lowering energy barriers for H-H recombination. It was found that primary (1°), 2°, and 3° alcohols are the most suitable to enhance reaction rate. © 2014 Wiley Periodicals, Inc.

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Sateesh Bandaru – One of the best experts on this subject based on the ideXlab platform.

  • Towards the design of novel boron- and nitrogen-substituted Ammonia-borane and bifunctional arene ruthenium catalysts for hydrogen storage
    Journal of computational chemistry, 2014
    Co-Authors: Sateesh Bandaru, Niall J. English, Andrew D. Phillips, J. M. D. Macelroy

    Abstract:

    Electronic-structure density functional theory calculations have been performed to construct the potential energy surface for H2 release from Ammonia-borane, with a novel bifunctional cationic ruthenium catalyst based on the sterically bulky β-diketiminato ligand (Schreiber et al., ACS Catal. 2012, 2, 2505). The focus is on identifying both a suitable substitution pattern for Ammonia-borane optimized for chemical hydrogen storage and allowing for low-energy dehydrogenation. The interaction of Ammonia-borane, and related substituted AmmoniaBoranes, with a bifunctional η6-arene ruthenium catalyst and associated variants is investigated for dehydrogenation. Interestingly, in a number of cases, hydride-proton transfer from the substituted Ammonia-borane to the catalyst undergoes a barrier-less process in the gas phase, with rapid formation of hydrogenated catalyst in the gas phase. Amongst the catalysts considered, N,N-difluoro Ammonia-borane and N-phenyl Ammonia-borane systems resulted in negative activation energy barriers. However, these types of AmmoniaBoranes are inherently thermodynamically unstable and undergo barrierless decay in the gas phase. Apart from N,N-difluoro Ammonia-borane, the interaction between different types of catalyst and Ammonia borane was modeled in the solvent phase, revealing free-energy barriers slightly higher than those in the gas phase. Amongst the various potential candidate Ru-complexes screened, few are found to differ in terms of efficiency for the dehydrogenation (rate-limiting) step. To model dehydrogenation more accurately, a selection of explicit protic solvent molecules was considered, with the goal of lowering energy barriers for H-H recombination. It was found that primary (1°), 2°, and 3° alcohols are the most suitable to enhance reaction rate. © 2014 Wiley Periodicals, Inc.

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Keith Fagnou – One of the best experts on this subject based on the ideXlab platform.

  • ruthenium catalyzed dehydrogenation of Ammonia Boranes
    Journal of the American Chemical Society, 2008
    Co-Authors: Nicole Blaquiere, Sarah Diallogarcia, Serge I Gorelsky, Daniel A Black, Keith Fagnou

    Abstract:

    The dehydrogenation of Ammonia borane (AB) and methylAmmonia borane (MeAB) is shown to be catalyzed by several Ru-amido complexes. Up to 1 equiv of H2 (1.0 system wt %) is released from AB by as little as 0.03 mol % Ru within 5 min, and up to 2 equiv of H2 (3.0 system wt %) are released from MeAB with 0.5 mol % Ru in under 10 min at room temperature, the first equivalent emerging within 10 s. Also, a mixture of AB/MeAB yields up to 3.6 system wt % H2 within 1 h with 0.1 mol % Ru. Computational studies were performed to elucidate the mechanism of dehydrogenation of AB. Finally, it was shown that alkylamine-Boranes can serve as a source of H2 in the Ru-catalyzed reduction of ketones and imines.

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