PUB - Publikationen an der Universität Bielefeld

The benzene radical anion (C6H6)●-, possessing a 7pi-electron count, is a crucial intermediate in the Birch reduction and has been extensively studied both experimentally and theoretically. Herein, we report the tricyclic pnictogen radical cations [(ADC)E]2[B], [2-E][B] (ADC = PhC{N(Dipp)C}2; Dipp = 2,6-iPr2C6H3; E = P, As, Sb; [B] = [B1] = B(C6F5)4 or [B2] = {3,5-(CF3)2C6H3}) featuring a central 7pi-electron planar C4E2 ring embedded between two 1,3-imidazole-based anionic dicarbene (ADC) frameworks, as crystalline solids. [2-E][B] are prepared by one-electron (1e) oxidations of the corresponding base-stabilized cyclic pnictinidene compounds [(ADC)E]2 (1-E). Calculated spin densities (for E = P 76%, As 80%, Sb 88%) and EPR measurements suggest that [2-E]●+ are pnictogen-centered radicals and stabilized by the delocalization of the unpaired electron over the C4E2 ring. The EPR spectra of [2-E][B] exhibit characteristic signals for S = systems with clear hyperfine coupling constants for the two similar P, As or Sb nuclei. Further 1e-oxidations of [2-E][B] result in the dicationic 6pi-electron C4E2-species [(ADC)E]2[B]2 [3-E][B]2, which readily undergo comproportionations with 1-E to afford [2-E][B]. The radical reactivity of [2-E][B2] is shown with 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) and diphenyl diselenide (PhSeSePh) in yielding compounds [(ADC)2E{E(TEMPO)}][B2] (4-E) (E = P, Sb) and [(ADC)2P{P(SePh)}][B2] (5-P), respectively. © 2025 Wiley‐VCH GmbH.