Tricoordinate Nontrigonal Pnictogen-Centered Radical Anions: Isolation, Characterization, and Reactivity

The search for main-group element-based radicals is one of the main research topics in contemporary chemistry because of their fascinating chemical and physical properties. The Group 15 element-centered radicals mainly feature a V-shaped two coordinate structure, with a couple of radical cations featuring trigonal tricoordinated geometry. Now, nontrigonal compounds R₃ E (E=P, As, Sb) were successfully synthesized by introducing a new rigid tris-amide ligand. The selective one-electron reduction of R₃ E afforded the first stable tricoordinate pnictogen-centered radical anion salts; the pnictogen atoms retain planar T-shaped structures. EPR spectroscopy and calculations reveal that the spin density mainly resides at the p orbitals of the pnictogen atoms, which is perpendicular to the N₃ E planes.