Dinuclear Ru-aqua complexes for selective epoxidation catalysis based on supramolecular substrate orientation...

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Alkene epoxidation is a crucial transformation in organic synthesis.
• Development of efficient and stereoselective epoxidation catalysts remains a key challenge.
• Ruthenium complexes have shown promise as catalysts for various oxidation reactions.

Purpose of the Study:

• To investigate the catalytic activity of a novel Ru-aqua complex for alkene epoxidation.
• To evaluate the stereospecificity and reactivity of the catalyst towards different olefin substrates.
• To elucidate the mechanistic aspects governing the catalytic performance.

Main Methods:

• Synthesis and characterization of the Ru-aqua complex {[Ru(II)(trpy)(H2O)]2(μ-pyr-dc)}(+).
• Epoxidation reactions using various linear and cyclic alkenes with PhIO as the oxidant.
• Electrochemical techniques and Density Functional Theory (DFT) calculations for mechanistic studies.

Main Results:

• The Ru-aqua complex demonstrated high catalytic activity, achieving turnover numbers (TNs) up to 17000 and turnover frequencies (TOFs) up to 24120 h⁻¹.
• Exceptional stereospecificity was observed for both cis and trans olefins, yielding corresponding epoxides.
• Differential reactivity towards cis and trans olefins was attributed to a substrate orientation supramolecular effect.

Conclusions:

• The Ru-aqua complex is a highly effective epoxidation catalyst for a broad range of alkenes.
• The catalyst's stereospecificity and substrate selectivity are governed by its unique ligand scaffold.
• Electrochemical and computational studies provide insights into the reaction mechanism and catalyst performance.