Jorgensen, Mathias Lee, Young-Su Bjerring, Morten Jepsen, Lars H. Akbey, Umit Cho, Young Whan Jensen, Torben R. 2024-01-19T21:04:05Z 2024-01-19T21:04:05Z 2021-09-05 2018-12-14 1477-9226 https://pubs.kist.re.kr/handle/201004/120572 The new compound Sr(BH4)(2)(NH3BH3)(2) has been synthesized and characterized with in situ powder X-ray diffraction and fast (28 or 60 kHz) magic angle spinning H-1, B-11 and N-15 NMR and structurally optimized with density functional theory calculations. This investigation reveals complex structural rearrangements for this compound as a function of temperature. A room temperature orthorhombic polymorph, -Sr(BH4)(2)(NH3BH3)(2), with the space group symmetry Pbca, has been determined with a layered structure of alternating ammonia borane and Sr(BH4)(2), partially stabilized by dihydrogen bonding. Surprisingly the crystal symmetry is lowered upon heating, as evidenced both by in situ synchrotron powder X-ray diffraction and B-11 MAS NMR data, resulting in an intermediate polymorph, -Sr(BH4)(2)(NH3BH3)(2), present from approximate to 65 to 115 degrees C. -Sr(BH4)(2)(NH3BH3)(2), a sub structure of the -polymorph showing higher symmetry with the space group symmetry Aba2, forms upon further heating. Ab initio molecular dynamics simulations show that the ammonia borane molecule can dynamically alternate between a bidentate and a tridentate coordination to Sr at finite temperature. The dynamic properties of the ammonia borane molecule in the solid state are suggested to cause the observed structural complexity. Based on simultaneous thermogravimetric analysis, differential scanning calorimetry and mass spectrometry, the decomposition of the compound was investigated showing a stabilization of ammonia borane in the structure relative to other metal borohydride ammonia boranes and neat ammonia borane. English ROYAL SOC CHEMISTRY AMMONIA-BORANE THERMAL-DECOMPOSITION METAL BOROHYDRIDES STORAGE PROPERTIES DEHYDROGENATION AMIDOBORANE HYDRIDES COMPLEX AMIDOTRIHYDROBORATE LITHIUM Disorder induced polymorphic transitions in the high hydrogen density compound Sr( BH4) 2( NH3BH3) 2+ Article 10.1039/c8dt03654c 1 DALTON TRANSACTIONS, v.47, no.46, pp.16737 - 16746 DALTON TRANSACTIONS 47 46 16737 16746 scie scopus 000451657900043 2-s2.0-85057163973 Chemistry, Inorganic & Nuclear Chemistry Article AMMONIA-BORANE THERMAL-DECOMPOSITION METAL BOROHYDRIDES STORAGE PROPERTIES DEHYDROGENATION AMIDOBORANE HYDRIDES COMPLEX AMIDOTRIHYDROBORATE LITHIUM hydrogen storage