Deprotonation of a Hydridoborate Anion

The first deprotonation of a borohydride anion was achieved by treatment of [BH(CN) 3 ] − with strong non‐nucleophilic bases, which resulted in the formation of alkali‐metal salts of the tricyanoborate dianion B(CN) 3 2− in up to 97 % yield and 99.5 % purity. [BH(CN) 3 ] − is less acidic than (Me 3 Si) 2 NH but a stronger acid than i Pr 2 NH. Less sterically hindered, more nucleophilic bases such as PhLi and MeLi mostly attack a CN group under formation of imine dianions [RC(N)B(CN) 3 ] 2− , which can be hydrolyzed to ketones of the [RC(O)B(CN) 3 ] − type. The boron‐centered nucleophile B(CN) 3 2− reacts with CO 2 and CN + reagents to give salts of the [B(CN) 3 CO 2 ] 2− dianion and the tetracyanoborate anion [B(CN) 4 ] − , respectively, in excellent yields.