A Persistent Dipotassium 1,2,4-Diazaphospholide Radical Complex: Synthesis, X-Ray Structure, and Bonding

摘要

What happens when an electron is added to a five-membered heterocyclic ring obeying the 4n + 2 Huckel rule? If a 7-π-electron system results, is the aromaticity destroyed? Early and more recent evidence on persistent radicals containing low-valent Group 15 elements is inconclusive. Phosphorus-based aromatic ring systems (e.g., phosphinine, biphosphi-nine, planar phospholes, 1,2,4-triphosphole), especially those with (σ~2λ~3) P atoms, have low-lying π* lowest unoccupied molecular orbitals (LUMOs) owing to effective σ*(P-R)-π*(1,3-diene) orbital interactions and might accommodate extra electrons.