Synthesis, structure, and electrochemical properties of [LNi(Rf)(C4F8)]− and [LNi(Rf)3]− complexes

Abstract

The new anionic nickelate complexes [(MeCN)Ni(C₄F₈)(CF₃)]⁻, [(MeCN)Ni(C₄F₈)(C₂F₅)]⁻, [(IMes)Ni(C₄F₈)(CF₃)]⁻, [(IMes)Ni(CF₃)₃]⁻ (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), and [(F-NHC)Ni(R_f)₃]⁻ (F-NHC = 1,3-bis(2,4-F₂Ph), 2,4,6-F₃Ph- or 3,4,5-F₃Ph)imidazol-2-ylidene; (R_f = CF₃ or C₂F₅) were synthesized and structurally characterized. The electrochemical properties of all new compounds were revealed by cyclic voltammetry studies and compared to the known CF₃ analogue [(MeCN)Ni(CF₃)₃]⁻. The IMes-coordinated complexes exhibited initial oxidation events that were well-separated from a second oxidation process in the cyclic voltammograms. The complexes containing F-substituted NHC ligands [(F-NHC)Ni(CF₃)₃]⁻ are structurally quite similar to the IMes derivative and reveal also two separated oxidation waves in their cyclic voltammograms. The absolute potentials as well as the separation between the two waves vary with the substitution pattern, suggesting that the NHC ligand environment (NHC = N-heterocyclic carbene) is an interesting platform for the development of new redox-triggered reactions that release trifluoromethyl and perfluoroalkyl radicals upon oxidation.