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Generation and Nitric Oxide Reactivity of a Cobalt(II) Superoxide Complex via Guanidine-Based Ligand Non-Innocence

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide A novel guanidine-based NNN pincer cobalt(II) complex, Co1, was investigated for dioxygen (O 2 ) activation. Upon reaction with O 2 at room temperature, a μ-hydroxo-bridged Co II –OH-Co II complex ( Co2 ) was isolated as the final oxygenated product. In-depth spectroscopic investigation revealed that the formation of Co2 occurs via an intermediate superoxide species ( Co1–O 2 •– ), by taking advantage of the redox non-innocence behavior of the ligand (3,3′-(pyridine-2,6-diyl)bis(1-methyl- N -phenylimidazolidin-2-imine)), and therefore keeping the cobalt oxidation state unchanged at +2. Interestingly, the zinc analogue, Zn1, was also shown to yield a similar μ-hydroxo-bridged Zn II –OH-Zn II complex ( Zn2 ) as the final product under the same aerobic conditions, providing further confirmation of the ligand influence on metal oxidation and spin states during O 2 activation. Further reactivity studies demonstrated that Co1–O 2 •– reacts with nitric oxide ( • NO) to form a Co II -peroxynitrite ( Co1–O NO 2 – ) intermediate, which performs an unprecedented intramolecular nitration of the phenyl moieties of the ligand at the para position.

Source: JACS Au

DOI: 10.1021/jacsau.5c00418