Formation of a Cobalt(III)-Phenoxyl Radical Complex by Acetic Acid Promoted Aerobic Oxidation of a Co(II)salen Complex

Vinck, Evi, Murphy, Damien Martin ORCID: https://orcid.org/0000-0002-5941-4879, Fallis, Ian Andrew ORCID: https://orcid.org/0000-0001-7361-0182, Strevens, Robert Ross and Van Doorslaer, Sabine 2010. Formation of a Cobalt(III)-Phenoxyl Radical Complex by Acetic Acid Promoted Aerobic Oxidation of a Co(II)salen Complex. Inorganic Chemistry 49 (5) , pp. 2083-2092. 10.1021/ic901849e

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Abstract

The activation of N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino CoII, [CoII(1)], by the addition of acetic acid under aerobic conditions has been investigated by a range of spectroscopic techniques including continuous-wave EPR, HYSCORE, pulsed ENDOR, and resonance Raman. These measurements have revealed for the first time the formation of a coordinated cobalt(III)-bound phenoxyl radical labeled [CoIII(1•)(OAc)n](OAc)m (n = m = 1 or n = 2, m = 0). This cobalt(III)-bound phenoxyl radical is characterized by the following spin Hamiltonian parameters: gx = 2.0060, gy = 2.0031, gz = 1.9943, Ax = 17 MHz, Ay = 55 MHz, and Az = 14 MHz. Although the radical contains coordinated acetate(s), the experiments unambiguously proved that the phenoxyl radical is situated on ligand (1) as opposed to a phenoxyl radical ligated to cobalt in the axial position. Density functional theory computations on different models corroborate the stability of such a phenoxyl radical species and suggest the ligation of one or two acetate molecules to the complex. A mechanism is proposed, which accounts for the formation of this unusual and extremely robust phenoxyl radical, never previously observed for [Co(1)].

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	American Chemical Society
ISSN:	0020-1669
Funders:	EPSRC
Last Modified:	18 Oct 2022 13:12
URI:	https://orca.cardiff.ac.uk/id/eprint/12969

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