P-H activation using alkynylgold substrates: steric and electronic effects

Area of Science:

• Organometallic Chemistry
• Catalysis
• Phosphorus Chemistry

Background:

• Gold complexes are effective catalysts for various organic transformations.
• P-H activation is a key step in functionalizing phosphonates.
• Alkynylgold complexes offer unique reactivity profiles.

Purpose of the Study:

• To investigate the P-H activation of hydrogen phosphonates using alkynylgold complexes.
• To understand the influence of ligands and substrate structure on reaction dynamics and rates.
• To elucidate the reaction mechanism.

Main Methods:

• Synthesis of alkynylgold complexes with varying ligands (triphenylphosphine, bulky biaryldialkylphosphines, N-heterocyclic carbenes).
• Reaction of these complexes with hydrogen phosphonates.
• Analysis of reaction kinetics and product distributions.
• Computational studies to explore potential mechanisms.

Main Results:

• Alkynylgold complexes efficiently promote P-H activation of hydrogen phosphonates.
• Fluxional behavior was observed with triphenylphosphine ligands due to ligand exchange.
• Bulky phosphine ligands and N-heterocyclic carbenes stabilized the complexes but did not significantly alter P-H activation rates.
• Electron-donating groups on the alkyne accelerated the reaction, while electron-withdrawing groups decelerated it.
• Product distributions were generally unaffected by incorporating propargyl alcohol moieties.

Conclusions:

• The P-H activation of hydrogen phosphonates by alkynylgold complexes is a viable synthetic route.
• Ligand choice impacts reaction dynamics but not the fundamental P-H activation step.
• Electronic properties of the alkyne significantly influence reaction rates.
• Potential for gold-catalyzed reactions involving alkynylgold intermediates requires careful consideration of labile P-H donors to avoid catalyst/intermediate interception.