Mixed N3S2-Ligated Nonheme Fe(IV)=O Species Balancing Stability and Oxidation Reactivity as a Platform for Nonheme Iron Oxidation Catalysis

Mansour H, Albasiony AM, Abdou SN, Ibrahim MM, van Eldik R, Shaban SY (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Catalysts MDPI

Book Volume: 16

Article Number: 631

Journal Issue: 7

DOI: 10.3390/catal16070631

Abstract

Mononuclear nonheme iron(IV)–oxo species supported by mixed nitrogen–sulfur (N/S) ligands remain scarce, despite the prevalence of sulfur donors in biological iron sites and their expected impact on ferryl reactivity and catalyst design. In this work, a seven-coordinate iron(II) complex, [(N3S2)Fe^II(ClO4)2], bearing a rigid 15-membered N3S2 macrocycle, is shown to rapidly generate a mononuclear nonheme Fe^IV=O intermediate upon reaction with m-chloroperbenzoic (m-CPBA) acid in acetonitrile. The Fe^IV=O species forms within ≤2 s and is thermally persistent (t1/2 = 4.3 h at 25 °C), albeit in partial yield (~39% Fe^IV=O by Mössbauer spectroscopy), placing it in an intermediate regime between highly reactive but short-lived ferryl species and more inert, long-lived analogues. The intermediate is characterized by Mössbauer spectroscopy (δ = 0.35 mm s⁻¹, ΔEQ = 0.90 mm s⁻¹, ΓFWHM = 0.30 mm s⁻¹, relative area = 39.4%), EPR silence, a UV–vis absorption band at 428 nm, and cryogenic high-resolution ESI–MS (m/z 223.510, (N3S2)Fe^IV=O²⁺). Stopped-flow kinetic studies reveal saturation behavior that is well described by a pre-equilibrium oxidant-association model and subsequent O–O bond activation, with apparent activation parameters of ΔH^‡ = 17.7 kJ mol⁻¹ and ΔS^‡ = −155 J mol⁻¹ K⁻¹, indicating a highly ordered transition state within the seven-coordinate N3S2 framework under the conditions employed. Functionally, the Fe^IV=O species mediates clean oxygen-atom transfer to triphenylphosphine (k2 = 8.1 × 10⁻² M⁻¹ s⁻¹) with an effective turnover number of ~12 after correction for the Fe^IV=O yield, establishing that this mixed N/S platform is catalytically competent under mild conditions, though less reactive than state-of-the-art all-nitrogen systems. Collectively, these findings identify the seven-coordinate N3S2 macrocycle as a mixed-donor platform that moderately extends ferryl lifetime while retaining measurable oxo-transfer reactivity, providing mechanistic guidance for the development of nonheme iron oxidation catalysts that incorporate sulfur donors.

Authors with CRIS profile

Rudi van Eldik Naturwissenschaftliche Fakultät

Involved external institutions

Taif University / جامعة الطائف

Saudi Arabia (SA)

How to cite

APA:

Mansour, H., Albasiony, A.M., Abdou, S.N., Ibrahim, M.M., van Eldik, R., & Shaban, S.Y. (2026). Mixed N3S2-Ligated Nonheme Fe(IV)=O Species Balancing Stability and Oxidation Reactivity as a Platform for Nonheme Iron Oxidation Catalysis. Catalysts, 16(7). https://doi.org/10.3390/catal16070631

MLA:

Mansour, Hanaa, et al. "Mixed N3S2-Ligated Nonheme Fe(IV)=O Species Balancing Stability and Oxidation Reactivity as a Platform for Nonheme Iron Oxidation Catalysis." Catalysts 16.7 (2026).

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