Reactivity of Highly Lewis-Acidic Diborane(4) toward C≡N and N=N Bonds: Uncatalyzed Addition and N=N Bond-Cleavage Reactions.

The diboration of the C≡N bond in organic nitriles, and the N=N bond in azobenzene and pyridazine, by the highly Lewis-acidic tetra(o-tolyl)diborane(4) are reported. In the reactions with nitriles, azobenzene, and pyridazine, the addition of diborane(4) to the C≡N and N=N bonds was observed. Conversely, the N=N bond in phthalazine was cleaved by an addition/rearomatization sequence.