Synthesis, structures and thermal decomposition of ammine MxB12H12 complexes (M = Li, Na, Ca)

Bjarne R.S. Hansen, Nikolay Tumanov, Antonio Santoru, Claudio Pistidda, Jozef Bednarcik, Thomas Klassen, Martin Dornheim, Yaroslav Filinchuk, Torben R. Jensen

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Abstract

A series of ammine metal-dodecahydro-closo-dodecaboranes, MxB12H12·nNH3 (M = Li, Na, Ca) were synthesized and their structural and thermal properties studied with in situ time-resolved synchrotron radiation powder X-ray diffraction, thermal analysis, Fourier transformed infrared spectroscopy, and temperature-programmed photographic analysis. The synthesized compounds, Li2B12H12·7NH3, Na2B12H12·4NH3 and CaB12H12·6NH3, contain high amounts of NH3, 43.3, 26.6 and 35.9 wt% NH3, respectively, which can be released and absorbed reversibly at moderate conditions without decomposition, thereby making the closo-boranes favorable 'host' materials for ammonia or indirect hydrogen storage in the solid state. In this work, fifteen new ammine metal dodecahydro-closo-dodecaborane compounds are observed by powder X-ray diffraction, of which six are structurally characterized, Li2B12H12·4NH3, Li2B12H12·2NH3, Na2B12H12·4NH3, Na2B12H12·2NH3, CaB12H12·4NH3 and CaB12H12·3NH3. Li2B12H12·4NH3 and Na2B12H12·4NH3 are isostructural and monoclinic (P21/n) whereas Na2B12H12·2NH3 and CaB12H12·3NH3 are both trigonal with space groups P3m1 and R3c, respectively. Generally, coordination between the metal and the icosahedral closo-borane anion is diverse and includes point sharing, edge sharing, or face sharing, while coordination of ammonia always occurs via the lone pair on nitrogen to the metal. Furthermore, a liquid intermediate is observed during heating of Li2B12H12·7NH3. This work provides deeper insight into the structural, physical, and chemical properties related to thermal decomposition and possible ammonia and hydrogen storage.

Original languageEnglish
Pages (from-to)7770-7781
Number of pages12
JournalDalton Transactions
Volume46
Issue number24
DOIs
Publication statusPublished - 30 May 2017

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  • Datasets

    CCDC 1489211: Experimental Crystal Structure Determination

    Bednarcik, J. (Contributor), Dornheim, M. (Contributor), Filinchuk, Y. (Contributor), Hansen, B. R. S. (Contributor), Jensen, T. R. (Contributor), Klassen, T. (Contributor), Pistidda, C. (Contributor), Santoru, A. (Contributor) & TUMANOV, N. (Contributor), Cambridge Crystallographic Data Centre, 1 Jan 2017

    Dataset

    CCDC 1489213: Experimental Crystal Structure Determination

    Bednarcik, J. (Contributor), Dornheim, M. (Contributor), Filinchuk, Y. (Contributor), Hansen, B. R. S. (Contributor), Jensen, T. R. (Contributor), Klassen, T. (Contributor), Pistidda, C. (Contributor), Santoru, A. (Contributor) & TUMANOV, N. (Contributor), Cambridge Crystallographic Data Centre, 1 Jan 2017

    Dataset

    CCDC 1489214: Experimental Crystal Structure Determination

    Bednarcik, J. (Contributor), Dornheim, M. (Contributor), Filinchuk, Y. (Contributor), Hansen, B. R. S. (Contributor), Jensen, T. R. (Contributor), Klassen, T. (Contributor), Pistidda, C. (Contributor), Santoru, A. (Contributor) & TUMANOV, N. (Contributor), Cambridge Crystallographic Data Centre, 1 Jan 2017

    Dataset

    Cite this

    Hansen, B. R. S., Tumanov, N., Santoru, A., Pistidda, C., Bednarcik, J., Klassen, T., Dornheim, M., Filinchuk, Y., & Jensen, T. R. (2017). Synthesis, structures and thermal decomposition of ammine MxB12H12 complexes (M = Li, Na, Ca). Dalton Transactions, 46(24), 7770-7781. https://doi.org/10.1039/c7dt01414g