Two-Electron Redox Tuning of Cyclopentadienyl Cobalt Complexes Enabled by the Phenylenediamide Ligand

01 March 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


A family of neutral cobalt complexes, [CpR'Co(Ropda)] 1-5, based on the redox-active o-phenylenediamide ligand (Ropda) undergo reversible 2e- oxidation revealed by cyclic voltammetry. This multielectron behavior is observed for all complexes regardless of the substituents on the phenylenediamide ligand, enabling redox tuning over more than 0.5 V. These diamagnetic neutral complexes are best described as delocalized systems with covalent bonding across the cobalt-opda metallocycle, consistent with the closed-shell singlet ground-state predicted by density functional theory (DFT) calculations. Two-electron oxidation using chemical oxidants affords the dicationic species, which are formulated as Co(III)-benzoquinonediimine systems with an additional coordinated acetonitrile ligand. DFT calculations also predict an ECE pathway for the 2e- oxidation, in which the first 1e- step is primarily a ligand-based process with redistribution of electron density to the metal. The associated distortion of the coordination geometry and disruption of the metallocycle bonding enable acetonitrile coordination in the intermediate oxidation state, which is critical for favoring the second electron transfer and accessing the potential inversion.


Redox-Active Ligands
Cobalt Complexes
Two-electron Oxidation
Potential Inversion
Cyclic Voltammetry

Supplementary materials

Supporting Information
Experimental procedures, crystallographic details, NMR spectra, cyclic voltammetry (CV) studies, electronic absorption spectra, computational results, and Cartesian coordinates for DFT calculated structures.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.