Recoverable Reusable Polyisobutylene (PIB)-Bound Ruthenium Bipyridine (Ru(PIB-bpy)3Cl2) Photoredox Polymerization Catalysts

Polyisobutylene (PIB)-bound ruthenium bipyridine [Ru(PIB-bpy)3]2+ metal complexes were prepared from PIB ligands formed by alkylation of 4,4′-dimethylbipyridine with polyisobutylene bromide. The product Ru(PIB-bpy)3Cl2 complexes with at least one PIB ligand per bipyridine unit function as soluble recyclable photoredox catalysts in free radical polymerization of acrylate monomers under visible light irradiation at 25 °C with ethyl 2-bromoisobutyrate as the initiator in the presence of diisopropylethylamine. The polyacrylate products contained only about 1 ppm Ru contamination. This PIB-bound catalyst was recyclable and showed about 50-fold less Ru leaching as compared to Ru leaching in a polymerization catalyzed by the low molecular weight Ru catalyst, Ru(bpy)3(PF6)2.