Hydrogenation of Carbon Dioxide to C₂–C₄ Hydrocarbons Catalyzed by Pd(P<i>t</i>Bu₃)₂–FeCl₂ with Ionic Liquid as Cocatalyst

Abstract

Direct hydrogenation of CO₂ to C₂₊ hydrocarbons is very interesting, but achieving this transformation below 200 °C is challenging and seldom reported. Herein, a homogeneous catalytic system was developed composed of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF₆ ]), Pd(PtBu₃ )₂ , FeCl₂ , and the ligand 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) for hydrogenation of CO₂ under mild conditions, which resulted in C₂ -C₄ hydrocarbons in selectivities up to 98.3 C-mol % at 180 °C. The combination of [BMIm][PF₆ ]) with Xantphos endowed the Pd-Fe catalysts with the ability of activating CO₂ and H₂ simultaneously via [HPd(PtBu₃ )(BMIm-COO)(BMIm)(PF₆ )Fe]⁺ species, thus catalyzing the formation of C₂ -C₄ hydrocarbons through CO₂ hydrogenation. In addition, this catalytic system is stable and recyclable, which may have promising applications.