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(NAr2)(3)] readily release aminyl radicals [NAr2](.) at ambient temperature in solution. These reactions yield the corresponding hydrazines, Ar2N-NAr2, 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 homologues 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.

Automated summary

The controlled release of aminyl radicals from bismuth amide species at ambient temperature enables selective N-N coupling reactions to yield hydrazines. Analyzes using various spectroscopy techniques and calculations reveal low homolytic bond-dissociation energies, suggesting radical coupling in the coordination sphere of bismuth, and demonstrate the effectiveness of electronic and steric parameters in controlling these reactions.