Hexanuclear and undecanuclear iron(III) carboxylates as catalyst precursors for cyclohexane oxidation

Area of Science:

• Inorganic Chemistry
• Catalysis
• Materials Science

Background:

• Iron carboxylates are versatile precursors for multinuclear iron complexes.
• Developing efficient catalysts for alkane oxidation is crucial for sustainable chemistry.
• Fenton-type chemistry offers a pathway for selective oxidation reactions.

Purpose of the Study:

• To synthesize and structurally characterize novel multinuclear iron complexes.
• To evaluate the catalytic activity of these complexes in cyclohexane oxidation.
• To investigate the mechanism of the catalytic process.

Main Methods:

• Synthesis of iron complexes from trinuclear iron(III) carboxylates.
• Structural characterization using X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements.
• Catalytic oxidation of cyclohexane using aqueous H2O2 and pyrazinecarboxylic acid.

Main Results:

• Two multinuclear iron complexes, [Fe6(μ3-O)2(μ4-O2)L10(OAc)2(H2O)2] (1) and [Fe(III)11Cl(μ4-O)3(μ3-O)5L16(dmf)(2.5)(H2O)(0.5)] (2), were successfully synthesized.
• Complex 1 features a hexanuclear {Fe6(O2)(O)2} core, while complex 2 contains an unprecedented undecanuclear {Fe11O8Cl} core with a deformed cubane entity.
• Both complexes demonstrated remarkable catalytic activity and good yields in cyclohexane oxidation, with complex 1 showing exceptionally high activity in a short reaction time.

Conclusions:

• The study presents novel multinuclear iron complexes with unique structural motifs.
• These complexes serve as efficient catalyst precursors for cyclohexane oxidation via Fenton-type chemistry.
• The findings highlight the potential of multinuclear iron complexes in developing advanced oxidation catalysts.