Synthesis of a Linear Tetraboron Cation via Deprotonation of a Nonsupported Dimeric Hydroborylborenium Ion

Abstract

Abstract The nonsupported B–H–B moiety of a dimeric hydroborylborenium ion can be readily deprotonated by 4‐(dimethylamino)pyridine, affording a H‐bridged linear tetraboron cation. The resulting tetraboron cation shows diverse reactivity with small molecules. Treatment of this tetraboron cation with H 2 leads to the first example of complete hydrogenolysis of main‐group homocatenated chains. On the other hand, in the presence of t BuNC, only the internal B–B bond of the tetraboron cation is cleaved, resulting in the formation of an azadiborabutadiene cation. Additionally, during the preparation of the hydroborylborenium, an unprecedented formal boryl cage‐walking was observed. Experimental and theoretical studies suggest this process involves consecutive activation of carboranyl B(9)–H bonds.