Reversible interconversion between a monomeric iridium hydroxo and a dinuclear iridium μ-oxo complex.

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis Research

Background:

• Metal hydroxo complexes are key intermediates in various catalytic reactions.
• Understanding their transformation into metal oxo species is vital for mechanistic studies.
• The synthesis and characterization of novel iridium complexes provide platforms for such investigations.

Purpose of the Study:

• To synthesize and characterize novel monomeric iridium(I) hydroxo complexes.
• To investigate the formation and structure of a dinuclear iridium oxo complex from the hydroxo precursor.
• To elucidate the mechanism of phenolysis of the dinuclear iridium oxo complex.

Main Methods:

• Synthesis of iridium hydroxo complexes via reaction of iridium chlorides with cesium hydroxide.
• Characterization using NMR (31P, 1H), IR spectroscopy, and X-ray crystallography.
• Kinetic studies employing varying phenol substrates and isotopic labeling (H/D).

Main Results:

• Efficient synthesis of monomeric iridium(I) hydroxo complexes (5R) in high yields.
• Formation of a dinuclear μ-oxo bridged iridium complex (6(iPr)) with a unique allene-like core.
• Kinetic data indicate a bimolecular reaction mechanism for phenolysis, with protonation of the μ-oxo ligand as the rate-limiting step.

Conclusions:

• The study successfully demonstrates the reversible condensation of metal hydroxo ligands to form metal oxo moieties.
• The dinuclear iridium oxo complex serves as a valuable model for studying oxo ligand reactivity.
• The findings offer a deeper understanding of reaction mechanisms involving metal-oxo intermediates in catalysis.