Bismuth Amides Mediate Facile and Highly Selective Pn-Pn Radical Coupling Reactions (Pn = N, P, As).

The controlled release of well-defined radical species under mild conditions for subsequent use in selective reactions is an important and challenging task in synthetic chemistry. We show here that simple bismuth amide species [Bi(NAr 2 ) 3 ] readily release aminyl radicals [NAr 2 ] ● at ambient temperature in solution. These reactions yield the corresponding hydrazines, Ar 2 N-NAr 2 , as a result of highly selective N-N coupling. The exploitation of facile homolytic Bi-Pn bond cleavage for Pn-Pn bond formation was extended to higher homologs of the pnictogens (Pn = N-As): homoleptic bismuth amides mediate the highly selective dehydrocoupling of HPnR 2 to give R 2 Pn-PnR 2 . Analyses by NMR and EPR spectroscopy, single crystal X-ray diffraction and DFT calculations reveal low Bi-N homolytic bond dissociation energies, suggest radical coupling in the coordination sphere of bismuth, and reveal electronic and steric parameters as effective tools to control these reactions.