A Crystalline Bismuth(II) Radical Anion: Synthesis, Characterization, and Reactivity

We report the synthesis of a planarized tris-amidobismuthane supported by a rigid, bulky NNN pincer ligand, which enforces a T-shaped geometry at the bismuth center. The Bi(NNN) complex features a low-lying LUMO with distinct Bi(6p) orbital character as shown by DFT calculations. Cyclic voltammetry reveals a fully reversible one-electron reduction at E_1/2 = -1.85 V versus Fc^0/+ in THF. Chemical reduction with KC₈ in the presence of 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (222-crypt) enables the isolation of an unprecedented Bi(II) radical anion in high isolated yields. Multi-frequency EPR, X-ray absorption spectroscopy and SQUID magnetometry complemented by theoretical calculations confirm localization of the unpaired electron on the bismuth center. Preliminary reactivity studies display radical reactivity as shown by single-electron transfer chemistry and radical coupling reactions.