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

Abstract

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.

Keywords: cyclic voltammetry; dpp-bian; electrochemistry; nickel; reduction.