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.

Impact of Methylaluminoxane Oxidation on Ethylene Polymerization Using Ni Catalysts

“…These two peaks were also observed when O 2 - or CO 2 -modified MAO was used, although the ratio of the intensities was different. A similar absorption was observed when Ni-diimine complex 3 was reduced chemically or electrochemically . According to the previous studies, the two absorptions would correspond to those of the solvated monomeric species and the dimeric form.…”

“…A similar absorption was observed when Ni-diimine complex 3 was reduced chemically or electrochemically. 53 According to the previous studies, the two absorptions would correspond to those of the solvated monomeric species and the dimeric form. We also performed theoretical estimations of the electronic transition using TD-DFT on the possible Ni(I) species.…”

Preparation of silyl-terminated branched polyethylenes catalyzed by Brookhart's nickel diimine complex activated with hydrosilane/B(C6F5)3

“…29,31 In the present case, the absence of aluminum compounds and the presence of borane B(C 6 F 5 ) 3 and hydrosilane in the SiHB activation system led us to suggest the possible structure of the observed Ni( i ) species as a cationic Ni( i ) complex (Chart 3) accompanied by a hydridoborate anion, where S denotes any coordinating species (solvent, hydrosilane, chlorosilane, or hydridoborate). The presence of a neutral monochloride or monohydride complex is less likely due to the formation of a dimeric structure, which was reported in the literature 33–36 The absence of Ni–alkyl or Ni–H bonds in the proposed Ni( i ) species precludes an olefin insertion; therefore, it could not be reactivated as was mentioned for the [(κ 2 - N , N -BIAN)Ni( i )(μ-Me) 2 AlMe 2 ] species.…”

Carbon Dioxide Electroreduction and Formic Acid Oxidation by Formal Nickel(I) Complexes of Di‐isopropylphenyl Bis‐iminoacenaphthene

“…We have selected the nickel(II) complex (dpp–bian)NiBr 2 ( I ) as a precatalyst for the electrochemical CO 2 reduction. The redox properties of this complex in an inert atmosphere were previously studied in detail [31] . On the cyclic voltammetry (CV) curve for I in a THF solution, four reversible reduction peaks are observed, corresponding to the successive metal–centered (Ni 2+/+/0 ) and ligand–centered (L 0/−/2− ) reductions.…”

“…This indicates that the genuine catalyst form is the three–electron–reduced nickel complex, which has not been studied before. It is noteworthy that the product of the one–electron reduction of (dpp–bian)NiBr 2 ( I ), namely [(dpp–bian)NiBr] 2 , has been already obtained and structurally characterized earlier [31] . In addition, analogues of nickel(0) complexes, namely (dpp–bian) 2 Ni ( II ) [32] and (dpp–bian)Ni(COD) ( III ), [33] have been previously synthesized and characterized.…”