A σ‐Donor with a Planar Six‐π‐Electron B2N2C2 Framework: Anionic N‐Heterocyclic Carbene or Heterocyclic Terphenyl Anion?

NB! The anionic ligand 2 was synthesized through deprotonation of a planar, formally zwitterionic diazadiborine precursor, isolated as a lithium salt, and structurally characterized. According to experimental evidence and theoretical calculations, 2 can be considered as an intermediate between two classical classes of ligands: N-heterocyclic carbenes 1 and terphenyls 3.