Structures of the strontium and barium dodecahydro-closo-dodecaborates

The structures of the anhydrous alkaline-earth-metal dodecahydro-closo-dodecaborates, SrB12H12 and BaB12H12, were determined by X-ray and neutron powder diffraction methods corroborated by a combination of neutron vibrational spectroscopic data and density-functional-theory-based phonon calculations. Both compounds possess the same novel trigonal structure with P31c space group symmetry, which appears to represent the most stable arrangement of alkaline-earth cations and dodecahydro-closo-dodecaborate anions for cations above a certain size.

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► The structures of SrB12H12 and BaB12H12 determined by powder diffraction have P31c symmetry.
► The structures were corroborated by vibrational spectra and DFT-based phonon calculations.
► Cation size vs. ionic arrangement of the alkaline-earth B12H12series was discussed.