Development of versatile and silver-free protocols for gold(I) catalysis

Area of Science:

• Organometallic Chemistry
• Catalysis
• Gold Chemistry

Background:

• N-heterocyclic carbene (NHC) ligands are crucial in stabilizing metal complexes.
• Gold(I) complexes are widely used as catalysts in organic synthesis.
• Understanding the active species in gold catalysis is essential for catalyst design.

Purpose of the Study:

• To investigate the in situ generation and characterization of active species from an NHC gold(I) hydroxide precatalyst.
• To identify and characterize any intermediates formed during the activation process.
• To evaluate the catalytic activity of the identified intermediates in gold(I) catalysis.

Main Methods:

• Synthesis and characterization of the [Au(OH)(IPr)] precatalyst.
• In situ generation of the active species using Brønsted acids.
• (1)H NMR spectroscopy in various solvents to monitor the reaction.
• Isolation and full characterization of the dinuclear gold hydroxide intermediate [{Au(IPr)}(2)(μ-OH)].

Main Results:

• The [Au(IPr)](+) ion, the presumed active species, is readily generated in situ from [Au(OH)(IPr)] by acid addition.
• A dinuclear gold hydroxide intermediate, [{Au(IPr)}(2)(μ-OH)], was identified and fully characterized.
• The dinuclear intermediate was found to be active in gold(I) catalysis, suggesting its potential role in catalytic cycles.

Conclusions:

• The [Au(OH)(IPr)] precatalyst offers a convenient route to the active [Au(IPr)](+) species.
• The discovery and characterization of the dinuclear gold hydroxide intermediate provide new insights into gold catalysis mechanisms.
• This study expands the understanding of NHC-gold complexes and their catalytic applications.