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Mechanistic Investigation on the Formation and Dehydrogenation of Calcium Amidoborane Ammoniate

Authors

  • Dr. Yong Shen Chua,

    1. Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
    2. Department of Chemistry, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore)
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  • Wen Li,

    1. Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore)
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  • Dr. Wendy J. Shaw,

    1. Pacific Northwest National Laboratory, PO Box 999, MSIN K2-57, Richland, WA 99354 (USA)
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  • Prof. Guotao Wu,

    Corresponding author
    1. Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
    • Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
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  • Dr. Tom Autrey,

    1. Pacific Northwest National Laboratory, PO Box 999, MSIN K2-57, Richland, WA 99354 (USA)
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  • Prof. Zhitao Xiong,

    Corresponding author
    1. Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
    • Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
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  • Prof. Ming Wah Wong,

    1. Department of Chemistry, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore)
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  • Prof. Ping Chen

    1. Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023 (PR China), Fax: (+86) 411 84685940
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Abstract

Possessing high H2 capacities and interesting dehydrogenation behavior, metal amidoborane ammoniates were prepared by reacting Ca(NH2)2, MgNH, and LiNH2 with ammonia borane to form Ca(NH2BH3)22 NH3, Mg(NH2BH3)2NH3, and Li(NH2BH3)2NH3 (LiAB⋅NH3). Insight into the mechanisms of amidoborane ammoniate formation and dehydrogenation was obtained by using isotopic labeling techniques. Selective 15N and 2H labeling showed that the formation of the ammoniate occurs via the transfer of one H(N) from ammonia borane to the [NH2] unit in Ca(NH2)2 giving rise to NH3 and [NH2BH3]. Supported by theoretical calculations, it is suggested that the improved dehydrogenation properties of metal amidoborane ammoniates compared to metal amidoboranes are a result of the participation of a strong dihydrogen bond between the NH3 molecule and [NH2BH3]. Our study elucidates the reaction pathway involved in the synthesis and dehydrogenation of Ca(NH2BH3)22 NH3, and clarifies our understanding of the role of NH3, that is, it is not only involved in stabilizing the structure, but also in improving the dehydrogenation properties of metal amidoboranes.

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