Immobilization of a chiral rhodium catalyst on carbon nanotubes via non-covalent interaction for heterogeneous asymmetric hydrogenation†

A new chiral rhodium complex containing a diphosphine ligand with a pyrene tag, Rh-(2S,4S)-PPM-pyrene, was synthesized. Its immobilization was achieved through non-covalent π–π stacking interaction between pyrene units of the ligand and multiwalled carbon nanotubes, leading to a hybrid material that was characterized by a set of analysis techniques. Strong adsorption of the complex onto the CNTs enabled an asymmetric hydrogenation of dimethyl itaconate under heterogeneous conditions. This hybrid catalyst showed reduced activity and enantioselectivity compared to its free complex but exhibited good stability for recycling.