An improved synthesis of unsolvated NaB3H8 and its application in preparing Na2B12H12

Octahydrotriborates are potential hydrogen storage materials and chemical vapor deposition precursors to boride films. Their syntheses have been quite challenging, however. In this paper, an improved facile route for the preparation of unsolvated sodium octahydrotriborate (NaB3H8), which is an important precursor to other octahydrotriborates and derivatives, is reported. The key steps in the synthesis involve dispersing Na finely in inert media and preparing fresh tetrahydrofuran (THF)·BH3 at room temperature. High purity unsolvated NaB3H8 can be obtained in tens of grams or more in one batch, depending on the reactor size. Using NaB3H8 as the precursor, sodium dodecaborate (Na2B12H12) has been successfully synthesized. Both octahydrotriborates and dodecaborates have been observed as intermediates during the thermal dehydrogenation of borohydrides, and their facile syntheses would facilitate mechanistic studies on the hydrogen storage of borohydrides, among other potential applications.