^(11)B NMR spectroscopy has been employed to identify the reaction intermediates and products formed in the amorphous phase during the thermal hydrogen desorption of metal tetrahydroborates (borohydrides) LiBH_4, Mg(BH_4)_2, LiSc(BH_4)_4, and the mixed Ca(AlH_4)_(2-)LiBH_4 system. The ^(11)B magic angle spinning (MAS) and cross polarization magic angle spinning (CPMAS) spectral features of the amorphous intermediate species closely coincide with those of a model compound, closo-borane K2B_(12)H_(12) that contains the [B_(12)H_(12)]^(2-) anion. The presence of [B_(12)H_(12)]^(2-) in the partially decomposed borohydrides was further confirmed by high-resolution solution ^(11)B and ^1H NMR spectra after dissolution of the intermediate desorption powders in water. The formation of the closo-borane structure is observed as a major intermediate species in all of the metal borohydride systems we have examined.
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Hwang et al. (2008) studied this question.
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