Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)-α-Hydroxy Acid Complexes

Area of Science:

• Bioinorganic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Aerobic organisms utilize iron enzymes for dioxygen activation and diverse oxidations.
• Mononuclear non-heme iron enzymes selectively transform substrates using dioxygen.
• Enzymatic reactions inspire synthetic catalysts for selective organic oxidations.

Purpose of the Study:

• To investigate iron(II)-α-hydroxy acid complexes as bioinspired catalysts for dioxygen reduction.
• To explore the role of sacrificial reductants in selective electron transfer for iron-catalyzed oxidations.
• To demonstrate the versatility of these complexes in generating reactive iron-oxygen species.

Main Methods:

• Utilized ternary iron(II)-α-hydroxy acid complexes with polydentate ligands.
• Investigated dioxygen reduction and subsequent oxidation reactions.
• Employed Lewis and protic acids as additives to tune reactivity.

Main Results:

• Iron(II)-coordinated α-hydroxy acids undergo oxidative decarboxylation, generating iron-oxygen oxidants.
• Generated oxidants include iron(II)-hydroperoxo, iron(IV)-oxo-hydroxo, and iron(IV)-oxo species.
• These oxidants perform alkene cis-dihydroxylation, C-H bond hydroxylation, and C-H bond halogenation.

Conclusions:

• Coordinated sacrificial reductants enable selective electron transfer for dioxygen activation by iron complexes.
• Ternary iron(II)-α-hydroxy acid complexes offer tunable reactivity for diverse oxidation reactions.
• This approach provides insights for developing environmentally benign catalytic methods using aerial oxygen.