We report the DFT study of the vibrational spectroscopy properties of Mg(B3H8)2, a potential intermediate in the decomposition of Mg(BH4)2, as well as those of CB11H12− and CB9H10−, whose salts can exhibit high ionic conductivities. Because the inclusion of anharmonicity is key to the accurate description of the vibrational properties of BH species [D. Sethio, L. M. Lawson Daku, H. Hagemann. Int. J. Hydrogen Energy, 41 (2016) 6814], the calculations were performed both in the harmonic and in the anharmonic approximation. The IR and Raman spectra of Cs(CB11H12) and Na2(B10H10) have also been measured. The calculated and experimental spectra are in good agreement. A comparative analysis of the vibrational spectroscopy properties is made for B3H8− and Mg(B3H8)2, B12H122− and CB11H12−, and for B10H102− and CB9H10−.