A Coordination-Induced 1,4→1,2-Quinonediimine Isomerization

Hitherto unused in coordination compounds, the para‐quinonoid azophenine (p‐ap) has now been applied for the synthesis of [Cu(PPh3)2(o‐ap)](BF4) (1), in which the ligand exists as its ortho‐quinonoid tautomer. Additional stabilization of this metal–π donor/ligand–π acceptor arrangement occurs through chelate‐like hydrogen bonding between the NH functionalities, which are both now ortho‐positioned, and the BF4− counterion.