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Electrochemical Reduction of [Ni(Mebpy)3]2+. Elucidation of the Redox Mechanism by Cyclic Voltammetry and Steady-State Voltammetry in Low Ionic Strength Solutions.

preprint
submitted on 31.01.2020, 21:48 and posted on 03.02.2020, 10:12 by Koushik Barman, Martin A. Edwards, David P. Hickey, Christopher Sandford, Yinghua Qiu, rui gao, Shelley D. Minteer, Henry White

Bipyridine complexes of Ni are used as catalysts in a variety of reductive transformations. Here, the electroreduction of [Ni(Mebpy)3]2+ (Mebpy = 4,4’-dimethyl-2,2’-bipyridine) in dimethylformamide is reported, with the aim of determining the redox mechanism and oxidation states of products formed under well-controlled electrochemical conditions. Results from cyclic voltammetry, steady-state voltammetry (SSV) and chronoamperometry demonstrate that [Ni(Mebpy)3]2+ undergoes two sequential 1e reductions at closely separated potentials (E0’1 = -1.06 ± 0.01 V and E02 = -1.15 ± 0.01 V vs Ag/AgCl (3.4 M KCl)). Homogeneous comproportionation to generate [Ni(Mebpy)3]+ is demonstrated in SSV experiments in low ionic strength solutions. The comproportionation rate constant is determined to be > 106 M-1s-1, consistent with rapid outer-sphere electron transfer. Consequentially, on voltammetric time scales, the 2e reduction of [Ni(Mebpy)3]2+ results in formation of [Ni(Mebpy)3]1+ as the predominant species released into bulk solution. We also demonstrate that [Ni(Mebpy)3]0 slowly loses a Mebpy ligand (~10 s-1).

Funding

CCI NSF Synthetic Organic Electrosynthesis Center (CHE-1740656)

EU for Horizon 2020 Marie Skłodowska-Curie Fellowship (grant no. 789399)

History

Email Address of Submitting Author

white@chem.utah.edu

Institution

University of Utah - Dept. of Chemistry

Country

United States

ORCID For Submitting Author

0000-0002-5053-0996

Declaration of Conflict of Interest

There are no conflicts of interest to declare.

Version Notes

About to be submitted version.

Exports