One‐Electron Reduction of Acenaphthene‐1,2‐Diimine Nickel(II) Complexes

New nickel‐based complexes of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene (dpp‐bian) with BF4− counterion or halide co‐ligands were synthesized in THF and MeCN. The nickel(I) complexes were obtained by using two approaches: 1) electrochemical reduction of the corresponding nickel(II) precursors; and 2) a chemical comproportionation reaction. The structural features and redox properties of these complexes were investigated by using single‐crystal X‐ray diffraction (XRD), cyclic voltammetry (CV), and electron paramagnetic resonance (EPR) and UV/Vis spectroscopy. The influence of temperature and solvent on the structure of the nickel(I) complexes was studied in detail, and an uncommon reversible solvent‐induced monomer/dimer transformation was observed. In the case of the fluoride complex, the unpaired electron was found to be localized on the dpp‐bian ligand, whereas all of the other nickel complexes contained neutral dpp‐bian moieties. Ni reduction: The one‐electron reduction of nickel(II) complexes with 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene (dpp‐bian) and BF4− counteranion or iodide, bromide, and chloride co‐ligands has been performed. As a result, monomeric and dimeric reduced nickel complexes with unpaired electron localization on nickel or the dpp‐bian moiety were found.