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

A cationic terminal iminoborane [MesN[triple bond, length as m-dash]B ← IPrMe][AlBr] (3[AlBr]) (Mes = 2,4,6-tri--butylphenyl and IPrMe = 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] 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 several synthetic routes.