Thermal studies of sodium tetrahydroborate–potassium tetrafluoroborate mixtures

Abstract

The results of DSC studies of NaBH₄–KBF₄ mixtures are presented. It is shown by chemical analysis, XRD analysis, IR spectroscopy, and ¹¹B and ⁹F MAS NMR that the decomposition of the mixtures starts at ~563 K to yield polyhedral borohydride compounds (predominantly B₁₂H₁₂^2-) in the solid residue. This temperature is much lower than the decomposition temperature of pure NaBH₄ (749 K). The mechanism of formation of the B₁₂H₁₂^2- anion has been proposed and confirmed. According to this mechanism, boron atoms from KBF₄ are involved in the formation of this anion.