Abstract: The application of functionalized ionic liquids (ILs) in homogeneous catalysis facilitates the reaction efficiency in homogeneous phase, liquid-liquid separation, and IL solvent-catalyst recycling. In this work, a series of P- or N-containing ligand functionalized imida-zolium-based ILs were synthesized and used in conjunction with common ambient imidazolium-based ILs to afford the IL solution, which acted as both the ligand and the solvent. In such functionalized IL compositions, RuCl3•3H2O catalyzed oxidation of various alcohols using O2 to aldehydes and ketones was achieved with high selectivity (most above 95%) in the absence of co-oxidants. The catalytic performance of the RuCl3•3H2O catalyst was greatly influenced by the solvents and ligands. The N-containing ligand functionalized IL with weaker liga-tion to Ru center exhibited better activity and much higher selectivity. Whereas, the N,P-hybrid ligand functionalized IL with bidentate che-lating ability to Ru center showed relatively low activity. However, the recyclability of RuCl3•3H2O in such functionalized IL compositions was unavailable. The in situ 31P NMR spectroscopy study indicated that the oxidative degradation of the ligand itself was responsible for the deactivation of the Ru catalyst.

Key words: functionalized ionic liquid, ruthenium catalyst, ligand, alcohol oxidation, molecular oxygen