Synthesis, structure and electrochemical properties of the organonickel complex [NiBr(Mes)(phen)] (Mes = 2,4,6-trimethylphenyl, phen = 1,10-phenanthroline)

•Electroreduction leads to formation of stable organonickel σ-complex [NiBr(Mes)(phen)].•Electron transfer to σ-complex [NiBr(Mes)(phen)] results in radical complex.•Unpaired electron in radical complex [Ni(Mes)(phen−)] is mainly located on nitrogen ligand.•Electroreduction of 1,10-phenanthroline produces stable radical anion in solution.

The organonickel complex [NiBr(Mes)(phen)] (1) (Mes = 2,4,6-trimethylphenyl, phen = 1,10-phenanthroline) was synthesized by oxidative addition of MesBr to nickel(0) complexes, obtained from [Ni(COD)2] (COD = 1,5-cyclooctadiene) and phen, or electrochemically generated from [NiBr2(phen)], and by ligand exchange reaction from [NiBr(Mes)(PPh3)2]. The electrochemical properties of [NiBr(Mes)(phen)] were investigated by cyclic voltammetry and in situ EPR spectroelectrochemistry. The cathodic reduction of 1 resulted in formation of the neutral radical complex [Ni(Mes)(phen−)] with a 1,10-phenanthroline radical anion bound to a nickel(II) centre. The electrochemical generation of the free 1,10-phenanthroline radical anion from 1,10-phenanthroline is also described.

Graphical abstractThe electrochemical reduction of organonickel σ-complex [NiBr(Mes)(phen)] (1) (Mes = 2,4,6-trimethylphenyl, phen = 1,10-phenanthroline) leads to formation of the coordinatively unsaturated neutral radical complex [Ni(Mes)(phen−)] where the unpaired electron is predominantly located on the 1,10-phenanthroline ligand. The electrochemical generation of the free 1,10-phenanthroline radical anion from 1,10-phenanthroline in solution is also described.Figure optionsDownload full-size imageDownload as PowerPoint slide