Highly reactive μ-carbido diiron tetraphenylporphine oxo-species: chemical generation and the oxidation ability

Abstract

The multistep interaction of a μ-carbido diiron tetraphenylporphine complex and its imidazole derivative with tert-butylhydroperoxide ^tBuOOH were investigated in benzene at 298 K by UV–visible, IR spectroscopy and electrochemical study. The kinetics of the stepwise processes were studied and their rate constants k were obtained. The reaction of both non-ligated [Fe^IVTPP]₂C (1) and [ImFe^IVTPP]₂C (2) with ^tBuOOH led to high-oxidized species generation following the coordination of a peroxide molecule on the metal center (k ₁ = 2.8 M⁻¹s⁻¹) and homolytic cleavage of O–O bond in attached ^tBuOOH (k ₂ = 3.1 s⁻¹ for 1, k ₂ = 12.8 s⁻¹ for 2). [Fe^IVTPP]₂C underwent one-electron ring oxidation to form a π-cation radical (k _ox = 3.9 s⁻¹) detected by UV–visible and IR spectroscopy. Imidazole-derivative formed a powerful oxidizing species that is able to oxidize the organic peroxide employed. The oxidant-intermediate reacting rapidly when produced in solution was proposed to be double-oxidized species due to its high reactivity (k _red = 2660 M⁻¹s⁻¹). The results of UV–visible, IR, ESI-MS study supported the final products with Fe = C=Fe unit.

Graphical Abstract

Keywords:

• µ-Carbido-bis[(tetra-phenylporphinato)iron(IV)]
• organic peroxide
• axial coordination
• oxidation
• highly-oxidized species
• kinetics

Acknowledgement

This work was carried out with the help of the centre of the scientific equipment collective use “The upper Volga region centre of physicochemical research.”

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Russian Foundation for Basic Research [grant number 18-03-00617-a].