Vibrational spectra and structure of borohydrides

A comparison of the vibrational spectra of many inorganic borohydrides allows us to distinguish compounds with isolated BH4- ions and compounds containing complex ions such as Sc(BH4)4-. The characteristic spectral features of both types of compounds are identified, showing that the B–H bonding is quite different in both cases. A detailed analysis of the vibrations of the isolated BH4- ions provides new information about their local structure. Angular deformations of individual borohydride ion are analyzed quantitatively. It appears that the compounds containing isolated BH4- ions belong to those with the most electropositive cations and the highest decomposition temperature, while the complex borohydrides show significantly lower decomposition temperatures and possible diborane formation