Polycationic Rh-JosiPhos Polymers Supported on Phosphotungstic Acid/Al2O3 by Multiple Electrostatic Attractions

Cationic Rh-JosiPhos complexes were tethered to crowded, ring-opening olefin metathesis (ROMP)-active norbornene groups. These monomers underwent facile, alternating ROMP (alt-ROMP) with cyclooctene as the co-monomer catalyzed by RuCl2(= CHPh)(PCy3)(2) to form linear, polycationic copolymers. The polymers were readily absorbed by phosphotungstic acid (PTA) on Al2O3 via multiple electrostatic attractions between the cationic Rh centers in the polymer and the PTA anions on the Al2O3 support. The enantioselective hydrogenation of dimethyl itaconate occurred with 100% conversion, 5000 turnovers per run, with up to 96% ee, and without significant Rh leaching over 10 reuses of the catalyst.

Automated summary

Cationic Rh-JosiPhos complexes were tethered to ROMP-active norbornene groups to form linear, polycationic copolymers. These copolymers could be readily absorbed onto PTA on Al2O3 via electrostatic attractions, and exhibited excellent catalytic activity and stability in enantioselective hydrogenation reactions.