Unraveling the reactivity of a cationic iminoborane: avenues to unusual boron cations.

A cationic terminal iminoborane [Mes*N[triple bond, length as m-dash]B ← IPr 2 Me 2 ][AlBr 4 ] (3 + [AlBr 4 ] - ) (Mes* = 2,4,6-tri- tert -butylphenyl and IPr 2 Me 2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) has been synthesized and characterized. The employment of an aryl group and N-heterocyclic carbene (NHC) ligand enables 3 + [AlBr 4 ] - to exhibit both B-centered Lewis acidity and BN multiple bond reactivities, thus allowing for the construction of tri-coordinate boron cations 5 + -12 + . More importantly, initial reactions involving coordination, addition, and [2 + 3] cycloadditions have been observed for the cationic iminoborane, demonstrating the potential to build numerous organoboron species via several synthetic routes.