Dodecaborates, i.e. the [B12H12]2- containing species, are often observed as main intermediates in the hydrogen sorption cycle of metal borohydrides, hindering rehydrogenation. In the decomposition process of Y(BH4)3, yttrium octahydrotriborate, i.e. Y(B3H8)3, rather than the stable Y2(B12H12)3, is formed as the main intermediate. © 2013 The Royal Society of Chemistry.