Issue 44, 2020

Electrocatalytic hydrogen production by dinuclear cobalt(ii) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study

Abstract

The chiral dicobalt(II) complex [CoII22-L)2] (1) (H2L = N2,N6-di(quinolin-8-yl)pyridine-2,6-dicarboxamide) and its tert-butyl analogue [CoII22-LBu)2] (2) were synthesized and structurally characterized. Addition of one equivalent of AgSbF6 to the dichloromethane solution of 1 and 2 resulted in the isolation of the mixed-valent dicobalt(III,II) species [CoIIICoII2-L)2]SbF6 (3) and [CoIIICoII2-LBu)2]SbF6 (4). Homovalent 1 and 2 exhibited catalytic activity towards proton reduction in the presence of acetic acid (AcOH) as the substrate. The complexes are stable in solution while their catalytic turnover frequency is estimated at 10 and 34.6 h−1 molcat−1 for 1 and 2, respectively. Calculations reveal one-electron reduction of 1 is ligand-based, preserving the dicobalt(II) core and activating the ligand toward protonation at the quinoline group. This creates a vacant coordination site that is subsequently protonated to generate the catalytically ubiquitous Co(III) hydride. The dinuclear structure persists throughout where the distal Co(II) ion modulates the reactivity of the adjacent metal site by promoting ligand redox activity through spin state switching.

Graphical abstract: Electrocatalytic hydrogen production by dinuclear cobalt(ii) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study

Supplementary files

Article information

Article type
Paper
Submitted
24 iyl 2020
Accepted
27 okt 2020
First published
28 okt 2020
This article is Open Access
Creative Commons BY license

Dalton Trans., 2020,49, 15718-15730

Electrocatalytic hydrogen production by dinuclear cobalt(II) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study

M. G. Papanikolaou, A. Elliott, J. McAllister, J. K. Gallos, A. D. Keramidas, T. A. Kabanos, S. Sproules and H. N. Miras, Dalton Trans., 2020, 49, 15718 DOI: 10.1039/D0DT02617D

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