An Improved Method for the Synthesis of [closo-B12(OH)12]-2.

The dicesium salt of the icosahedral borane anion dodecahydroxy-closo-dodecaborate(2−), closo-Cs2B12(OH)12, Cs24, was prepared using an improved synthetic pathway. Heating cesium dodecahydro-closo-dodecaborate, closo-Cs2B12H12, Cs21, with 30% hydrogen peroxide added in successive increments at 105−110 °C provided Cs24 in 95% yield. Reaction progress was monitored using 1H-decoupled 11B NMR while 17O NMR provides the most reliable way to detect the presence of peroxides in the reaction solution. The reaction may be safely increased in scale to afford Cs24 in multigram quantities.