Hydrolysis of the Borohydride Anion BH 4 - : A 11 B NMR Study Showing the Formation of Short-Living Reaction Intermediates including BH 3 OH .

In hydrolysis and electro-oxidation of the borohydride anion BH 4 - , key reactions in the field of energy, one critical short-living intermediate is BH 3 OH - . When water was used as both solvent and reactant, only BH 3 OH - is detected by 11 B NMR. By moving away from such conditions and using DMF as solvent and water as reactant in excess, four 11 B NMR quartets were observed. These signals were due to BH 3 -based intermediates as suggested by theoretical calculations; they were DMF·BH 3 , BH 3 OH - , and B 2 H 7 - (i.e., [H 3 B-H-BH 3 ] - or [H 4 B-BH 3 ] - ). Our results shed light on the importance of BH 3 stemming from BH 4 - and on its capacity as Lewis acid to interact with Lewis bases such as DMF, OH - , and BH 4 - . These findings are important for a better understanding at the molecular level of hydrolysis of BH 4 - and production of impurities in boranes synthesis.