Trapping of transient, heavy pnictogen-centred biradicals.

Since the heavy biradicals [E(μ-NTer)]2 (E = Sb, Bi) are only of fleeting existence in solution, they were generated in situ and trapped by [2 + 2] addition reactions utilizing alkynes such as tolan (Ph-C[triple bond, length as m-dash]C-Ph). The structure, biradical character and bonding of [E(μ-NTer)]2 biradicals as well as their addition products are discussed on the basis of computations and experimental data.