Medium Fluorous Separation Using Hydrofluoroether and Weakly Polar Solvents for Environmentally Friendly Recycling of Catalysts

As a novel approach to the separation of polyfluorinated compounds, we disclosed that HFE 7100 (methyl perfluorobutyl ether) forms with alkanes or chlorinated solvents two-layer systems between −51 and 30 °C depending on the nonfluorinated solvent. Similarly, more fluorinated HFE 7500 (ethyl perfluoroisoheptan-3-yl ether) forms the corresponding two-layer systems between −42 and 79 °C. While fluorinated compounds bearing 40–60% of fluorine were exclusively dissolved in the hydrofluoroether layer, nonfluorinated compounds strongly prevailed in the nonfluorinated solvent. The noncoordinating and aprotic character of the solvents used, as well as their low boiling points, enabled efficient isolation and recycling of sensitive polyfluoroalkylated Hoveyda–Grubbs second-generation precatalyst analogues. This medium fluorous method was further extended to the separation of various classes of polyfluorinated compounds including reaction intermediates, ligands, and ionic liquids. The key components of the medium fluorous separation system, hydrofluoroethers, are affordable, environmentally acceptable, and easily recyclable, as well as highly tolerable by sensitive transition-metal complexes