A Dianionic Dinickel(II) Complex and Its Oxidised Phenoxyl Radical States

The new dianionic dinickel(II) complex [NBu 4 ] 2 [Ni 2 (L) 2 ] {L 3– = trianionic form of 3,5‐di‐ tert ‐butyl‐2‐hydroxy‐ N ‐(2‐hydroxyethyl)benzamide} has been synthesised and characterised by 1 H, 13 C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X‐ray crystallography. The X‐ray structure of [NBu 4 ] 2 [Ni 2 (L) 2 ] · EtOH · CH 3 CN reveals a quasiplanar dinickel(II) dianionic complex, each of the Ni II ions possessing a NO 3 planar coordination sphere that results from the ligation of L 3– in a NO 2 fashion through the N ‐amidate, O ‐phenolate and O‐bridging alcoholate donor atoms. The cyclic voltammogram of [Ni 2 (L) 2 ] 2– reveals two one‐electron reversible oxidation processes at relatively low potentials. The EPR and UV/Vis spectroscopic characterisations of the electrochemically generated one‐electron‐ and two‐electron‐oxidised products are consistent with two ligand‐based oxidation processes leading to the formation of relatively stable mono‐ and diphenoxyl radical complexes, [Ni 2 (L · )(L)] – and [Ni 2 (L · ) 2 ], respectively.