New Ir Bis-Carbonyl Precursor for Water Oxidation Catalysis

Area of Science:

• Inorganic Chemistry
• Catalysis Science
• Materials Science

Background:

• Iridium complexes are crucial for homogeneous oxidation catalysis, particularly water oxidation.
• Previous iridium precursors like Cp*Ir(III)(pyalc)OH generate complex mixtures upon activation, hindering detailed analysis.
• The need for simpler, more characterizable precursors for understanding active catalytic species is evident.

Purpose of the Study:

• To introduce and evaluate Ir(I)(CO)2(pyalc) as an atom-efficient precursor for iridium-based homogeneous oxidation catalysis.
• To compare the chemical and catalytic properties of Ir(I)(CO)2(pyalc) with the established Cp*Ir(III)(pyalc)OH precursor.
• To facilitate a more detailed spectroscopic and catalytic examination of active iridium species in water oxidation.

Main Methods:

• Synthesis and characterization of the Ir(I)(CO)2(pyalc) complex.
• Comparative oxidative activation studies using NaIO4.
• Spectroscopic analysis (e.g., 1H NMR) of activated species.
• Catalytic evaluation in oxidation reactions.

Main Results:

• Oxidative activation of Ir(I)(CO)2(pyalc) yields Ir(pyalc) species without ligand degradation byproducts, unlike Cp*Ir precursors.
• The absence of degradation products allows for clearer catalytic and spectroscopic analysis of the active Ir(pyalc) species.
• Activated Ir(I)(CO)2(pyalc) systems require acetic acid or acetate to prevent nanoparticle formation.
• Fewer isomers are observed in activated Ir(I)(CO)2(pyalc) compared to activated Cp*Ir complexes, aiding characterization.

Conclusions:

• Ir(I)(CO)2(pyalc) is a valuable precursor for studying iridium-based oxidation catalysis due to its simpler activation pathway.
• This precursor enables more detailed structural and mechanistic investigations of active iridium species.
• Further research using this precursor is expected to enhance the understanding of active species in iridium-catalyzed oxidation reactions.