O₂ Activation by Non-Heme Thiolate-Based Dinuclear Fe Complexes

Area of Science:

• Bioinorganic Chemistry
• Organometallic Chemistry
• Coordination Chemistry

Background:

• Iron centers with thiolates are crucial for dioxygen activation in biological systems.
• Model complexes help elucidate the fundamental mechanisms of iron-thiolate reactivity.

Purpose of the Study:

• To investigate the structural and redox properties of a dinuclear iron-thiolate complex.
• To understand the reactivity of this complex with dioxygen under varying protonation conditions.
• To compare the dioxygen activation mechanism with manganese-thiolate analogues.

Main Methods:

• Synthesis and characterization of a dinuclear iron-thiolate complex.
• Reactivity studies with dioxygen under different protonation states.
• Single crystal X-ray diffraction, Mössbauer, resonance Raman, and NMR spectroscopy.
• Density functional theory (DFT) calculations.

Main Results:

• The dinuclear iron-thiolate complex reacts with dioxygen to form μ-oxo and μ-hydroxo iron(III) dinuclear complexes.
• The μ-oxo complex, [Fe^III₂(LS)₂O], was isolated and characterized for the first time via O₂ activation.
• Protonation influences the reaction pathway, leading to different oxygen-containing species or oxygen-free products.
• DFT calculations identified a dinuclear μ-peroxo iron(III) intermediate crucial for reactivity, whose structure is proton-dependent.

Conclusions:

• The protonation state of iron-thiolate complexes significantly dictates their dioxygen activation pathways.
• A common dinuclear μ-peroxo intermediate is involved, but its subsequent evolution differs between iron and manganese systems.
• This study provides insights into the factors controlling iron-thiolate reactivity towards O₂, relevant to biological and chemical catalysis.