Unveiling the power of additives: Enhancing Grubbs’ catalyst performance with phenol derivatives

Abstract

• Phenol derivatives enhance Grubbs’ second generation metathesis catalyst (GII) without structural modification. • UV–Vis, ATR-FTIR, and CV were used to study the electronic, stability, and transformation properties of GII-phenol adducts. • Electron-donating phenols correlate with faster catalyst activation and higher metathesis yield. • Electrochemical analysis shows phenol groups modulate GII’s redox potential and catalytic performance. Understanding the interaction between the Grubbs second-generation catalyst ( GII ) and phenol derivatives is key to enhancing metathesis reactions without structural modifications to commercially available catalysts. In this study, GII was employed for cross-metathesis reactions in the presence of various phenol derivatives, and the interactions were characterized using UV–Vis spectroscopy, ATR-FTIR, and cyclic voltammetry (CV). The ATR-FTIR spectra revealed distinct C N and C P stretching frequencies from the GII- phenol adducts, alongside phenol-associated O H and C C stretching bands. UV–Vis spectra displayed strong absorption bands at 335 nm and weaker bands between 503–509 nm, linked to metal–ligand charge transfer. Cyclic voltammetry showed electrochemical reversibility for most GII- phenol adducts, except those with electron-withdrawing groups. Metathesis reactions were performed between trans -1-methoxy-4-(1-propenyl)benzene and 2-ethylhexyl acrylate, revealing a correlation between electron-donating phenol groups and higher cross-metathesis (CM) yield. While phenol derivatives influenced catalyst activation rates, no direct correlation was found between activation rates and catalytic selectivity. The study highlights the significance of electron-donating phenol derivatives in enhancing catalytic efficiency by increasing Ru center electrophilicity.