Redox Interconversion between Cobalt(III) Thiolate and Cobalt(II) Disulfide Compounds

Feng Jiang, Maxime A. Siegler, Xiaobo Sun, Lin Jiang, Célia Fonseca Guerra*, Elisabeth Bouwman

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The redox interconversion between Co(III) thiolate and Co(II) disulfide compounds has been investigated experimentally and computationally. Reactions of cobalt(II) salts with disulfide ligand L1SSL1 (L1SSL1 = di-2-(bis(2-pyridylmethyl)amino)-ethyl disulfide) result in the formation of either the high-spin cobalt(II) disulfide compound [CoII 2(L1SSL1)Cl4] or a low-spin, octahedral cobalt(III) thiolate compound, such as [CoIII(L1S)(MeCN)2](BF4)2. Addition of thiocyanate anions to a solution containing the latter compound yielded crystals of [CoIII(L1S)(NCS)2]. The addition of chloride ions to a solution of [CoIII(L1S)(MeCN)2](BF4)2 in acetonitrile results in conversion of the cobalt(III) thiolate compound to the cobalt(II) disulfide compound [CoII 2(L1SSL1)Cl4], as monitored with UV-vis spectroscopy; subsequent addition of AgBF4 regenerates the Co(III) compound. Computational studies show that exchange by a chloride anion of the coordinated acetonitrile molecule or thiocyanate anion in compounds [CoIII(L1S)(MeCN)2]2+ and [CoIII(L1S)(NCS)2] induces a change in the character of the highest occupied molecular orbitals, showing a decrease of the contribution of the p orbital on sulfur and an increase of the d orbital on cobalt. As a comparison, the synthesis of iron compounds was undertaken. X-ray crystallography revealed that structure of the dinuclear iron(II) disulfide compound [FeII 2(L1SSL1)Cl4] is different from that of cobalt(II) compound [CoII 2(L1SSL1)Cl4]. In contrast to cobalt, reaction of ligand L1SSL1 with [Fe(MeCN)6](BF4)2 did not yield the expected Fe(III) thiolate compound. This work is an unprecedented example of redox interconversion between a high-spin Co(II) disulfide compound and a low-spin Co(III) thiolate compound triggered by the nature of the anion.

Original languageEnglish
Pages (from-to)8796-8805
Number of pages10
JournalInorganic Chemistry
Volume57
Issue number15
Early online date19 Jul 2018
DOIs
Publication statusPublished - 6 Aug 2018

Funding

F.J. and L.J. gratefully acknowledge the China Scholarship Council (CSC) for a personal grant (Nos. 201406890012 and 201406890016). The Netherlands Organization for Scientific Research (NWO−CW) is acknowledged for the financial support. We thank Mr. Anne Geert Volbeda, Jos van Brussel and Wim Jesse for ESI-MS analysis, Mr. Fons Lefeber for assistance with the NMR spectrometers. Dr. G. F. Schneider is acknowledged for use of the Raman spectrometer.

FundersFunder number
Netherlands Organization for Scientific Research
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
China Scholarship Council201406890012, 201406890016

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