Reductive C-C Coupling from Molecular Au(I) Hydrocarbyl Complexes: A Mechanistic Study

Area of Science:

• Organometallic Chemistry
• Catalysis
• Gold Complexes

Background:

• Organometallic gold complexes are vital precursors in catalytic reactions, particularly for carbon-carbon bond formation.
• Understanding the mechanisms of these reactions is crucial for designing more efficient catalytic systems.

Purpose of the Study:

• To investigate the C-C coupling reaction forming ethane from various phosphine-ligated gem-digold(I) methyl complexes.
• To elucidate the reaction mechanism, including the role of phosphine ligands and steric effects.

Main Methods:

• Synthesis of gem-digold methyl complexes via reaction of Au(CH3)L and Au(L)(NTf2).
• Solid-state X-ray structure determination for key complexes.
• Kinetic studies using multinuclear NMR spectroscopy to monitor ethane elimination rates.
• Computational methods to support mechanistic proposals.

Main Results:

• Ethane formation rate from [Au2(μ-CH3)(PMe2Ar')2][NTf2] is inversely related to the steric bulk of the Ar' phosphine substituent.
• Ethane elimination reactions exhibit a second-order dependence on the gem-digold methyl complexes.
• Solid-state X-ray structures were obtained for complexes with XPhos and tBuXPhos ligands.

Conclusions:

• A detailed mechanism for C-C coupling is proposed, involving complex dissociation, phosphine migration, and recombination.
• The Lewis acidity of gold fragments and steric properties of phosphine ligands significantly influence the reaction pathway and rate.
• This research provides fundamental insights into the reactivity of digold complexes in C-C bond formation.