Intriguing migrations in transient iminoborane adducts: two new pathways to aminoboranes

Two unusual reactions were demonstrated with iminoboranes, both leading to aminoboranes of the type R2B[double bond, length as m-dash]NR2. In one case, a carboboration of di(tert-butyl)iminoborane with B(C6F5)3 led to (tBu)(C6F5)B-N(tBu)(B(C6F5)2). In the other, a transient IDipp (1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) adduct of MesBNtBu undergoes a shift of one carbene-bound Dipp substituent to the iminoborane nitrogen atom, yielding (1-Dipp-imidazol-2-yl)(Mes)B-N(Dipp)(tBu). Mechanistic DFT studies indicate the intermediacy of a borane·iminoborane adduct in the carboboration reaction.