New perfluorinated rhodium–BINAP catalysts and hydrogenation of styrene in supercritical CO2

New perfluorinated BINAP ligands and their cationic rhodium complexes have been synthesized and characterized. The catalysts have been tested in homogeneous hydrogenation of the styrene in both methanol and supercritical carbon dioxide (scCO2). The selective hydrogenations of the styrene in scCO2 were carried out under the same reaction conditions of 343.15 K temperature and 120 bar CO2 pressure after 3 h (molar ratio of substrate to catalyst = 500). While all catalysts showed 100% conversion in methanol, same activity was not carried out in scCO2. (R)-6,6′-diperflorooktil-2,2′-bis(diphenylphosphino)-1,1′-binaphtyl-[Rh(COD)]BArF was showed the highest conversion (96.4%) in scCO2. Furthermore, methanol was used as co-solvent in the supercritical media in hydrogenation of styrene for the perfluorinated catalysts, which were inactive in scCO2. Addition of methanol in scCO2 has rather increased the conversion.

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