Structural Characterization of the [CuOR]²⁺ Core.

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Coordination Chemistry

Background:

• Highly reactive copper(III) species are typically transient and difficult to isolate and characterize.
• Understanding the electronic and structural properties of copper(III) is crucial for catalysis and bioinorganic chemistry.

Purpose of the Study:

• To stabilize and characterize elusive formal copper(III) complexes.
• To investigate the influence of ligand design on the stability and reactivity of copper(III) species.
• To explore the potential for detailed spectroscopic and crystallographic analysis of these reactive intermediates.

Main Methods:

• Synthesis of formal copper(III) complexes with oxygen-based auxiliary ligands ([CuOR]²⁺).
• Modulation of supporting ligand (L^Y) donor character and auxiliary ligand basicity.
• Characterization using Nuclear Magnetic Resonance (NMR) spectroscopy and X-ray crystallography.

Main Results:

• Successful stabilization of typically highly reactive copper(III) cores.
• First-time characterization of these copper(III) complexes by NMR spectroscopy and X-ray crystallography.
• Observed enhanced lifetimes in solution and slowed proton-coupled electron transfer (PCET) rates with a phenol substrate.
• NMR spectra confirmed singlet (S = 0) ground states.
• X-ray structures revealed shortened Cu-ligand bond distances consistent with theoretical calculations.

Conclusions:

• Ligand modulation provides a viable strategy for stabilizing reactive copper(III) complexes.
• The stabilized copper(III) complexes offer a platform for detailed mechanistic studies.
• These findings advance the understanding of copper redox chemistry and its implications in catalysis.