TY - JOUR
T1 - Desolvation and dehydrogenation of solvated magnesium salts of dodecahydrododecaborate
T2 - Relationship between structure and thermal decomposition
AU - Chen, Xuenian
AU - Liu, Yi Hsin
AU - Alexander, Anne Marie
AU - Gallucci, Judith C.
AU - Hwang, Son Jong
AU - Lingam, Hima Kumar
AU - Huang, Zhenguo
AU - Wang, Cong
AU - Li, Huizhen
AU - Zhao, Qianyi
AU - Ozkan, Umit S.
AU - Shore, Sheldon G.
AU - Zhao, Ji Cheng
PY - 2014/6/10
Y1 - 2014/6/10
N2 - Attempts to synthesize solvent-free MgB12H12 by heating various solvated forms (H2O, NH3, and CH 3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature-programmed desorption (TPD). Products were characterized by IR, solution- and solid-state NMR spectroscopy, elemental analysis, and single-crystal or powder X-ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14% and then 5.5%. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32% with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid-state 11B magic-angle spinning (MAS)NMR spectroscopy and X-ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H2O)6B12H12]η6H 2O and [Mg(CH3OH)6B12H 12]η6CH3OH, which were determined by single-crystal X-ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid-state hydrogen storage materials.
AB - Attempts to synthesize solvent-free MgB12H12 by heating various solvated forms (H2O, NH3, and CH 3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature-programmed desorption (TPD). Products were characterized by IR, solution- and solid-state NMR spectroscopy, elemental analysis, and single-crystal or powder X-ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14% and then 5.5%. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32% with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid-state 11B magic-angle spinning (MAS)NMR spectroscopy and X-ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H2O)6B12H12]η6H 2O and [Mg(CH3OH)6B12H 12]η6CH3OH, which were determined by single-crystal X-ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid-state hydrogen storage materials.
KW - X-ray diffraction
KW - boron
KW - hydrogen storage
KW - magnesium
KW - structure elucidation
UR - http://www.scopus.com/inward/record.url?scp=84902105484&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84902105484&partnerID=8YFLogxK
U2 - 10.1002/chem.201303842
DO - 10.1002/chem.201303842
M3 - Article
AN - SCOPUS:84902105484
VL - 20
SP - 7325
EP - 7333
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 24
ER -