Two-phase catalytic NBR hydrogenation by RuHCl(CO)(PCy3)2 immobilized in 1-butyl-3-methylimidazolium tetrafluoroborate molten salt

RuHCl(CO)(PCy₃)₂ ( 1 ) dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate ( 2 ) molten salt is able to reduce selectively NBR to HNBR under hydrogen partial pressures between 10 and 40 bar at 100–160°C in a typical two-phase catalytic reaction. Reaction rates between 0.059 (mmol Ru)⁻¹ · min⁻¹ and 1.65 (mmol Ru)⁻¹ · min⁻¹ were obtained depending on the reaction parameters and increasing with the volume of the molten salt. The overall process has an apparent activation energy of 47 ± 3 kJ · mol⁻¹. The recovered ionic catalyst solution can be reused several times without significant changes in the catalytic performance (selectivity and activity).