Deprotonation of a Hydridoborate Anion

Research paper by Johannes Landmann, Fabian Keppner, Daniel B. Hofmann, Dr. Jan A. P. Sprenger, Mathias Häring, Sven H. Zottnick, Prof. Dr. Klaus Müller‐Buschbaum, Dr. Nikolai V. Ignat'ev, Prof. Dr. Maik Finze

Indexed on: 25 Jan '17Published on: 24 Jan '17Published in: Angewandte Chemie International Edition


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)32− in up to 97 % yield and 99.5 % purity. [BH(CN)3]− is less acidic than (Me3Si)2NH but a stronger acid than iPr2NH. 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)32− reacts with CO2 and CN+ reagents to give salts of the [B(CN)3CO2]2− dianion and the tetracyanoborate anion [B(CN)4]−, respectively, in excellent yields.