Cu2 +-templated self-assembly of an asymmetric Salen–Cu(II) complex and its application in catalytic polymerization of methyl methacrylate (MMA)

•Cu2 +-templated self-assembly of asymmetric Schiff-base complex•Syndio-enriched atactic PMMA•Steric and electronic effects of ligand on catalytic activity and tacticity

With the mono-imine HL (HL = (E)-2-((2-aminophenylimino)methyl)-4,6-di-tert-butyl-phenol) as the precursor, an asymmetric Salen-type Schiff-base complex [Cu(L2)] (3, H2L2 = 2-((E)-2-((E)-2-hydroxybenzylideneamino)phenylimino)methyl-4,6-di-tert-butylphenol) was obtained by Cu2 +-templated approach in the presence of salicylaldehyde due to the formation of intermediate {[Cu(L)(OAc)]}2 (2)2. In contrast to the inertness for 2/AIBN system (AIBN = azobis(isobutyronitrile)), both the symmetric and asymmetric Salen-type Schiff-base complexes [Cu(L1)] (1, H2L1 = N, N′-bis(3,5-di-tert-butyl-salicylidene)phenylene-1,2-diamine) and [Cu(L2)] (3) as the catalysts in the presence of AIBN could effectively catalyze the solution polymerization of MMA (MMA = methyl methacrylate) for the formation of the syndio-enriched PMMAs, where the steric and the electronic effects of the ligands play an important and influential role on the catalytic behaviors, while on the premise of controllable polymerizations the variation of polymerization conditions almost has no effect on the polymer tacticity.

Graphical abstractAn asymmetric Salen-type Schiff-base complex [Cu(L2)] (3, H2L2 = 2-((E)-2-((E)-2-hydroxybenzylideneamino)phenylimino)methyl-4,6-di-tert-butylphenol) was obtained by Cu2+-templated approach due to the formation of intermediate {[Cu(L)(OAc)]}2 (2)2. In contrast to the inertness for 2/AIBN system (AIBN = azobis(isobutyronitrile)), both [Cu(L1)] (1, H2L1 = N, N’′-bis(3,5-di-tert-butyl-salicylidene)phenylene-1,2-diamine) and 3 could effectively catalyze the polymerization of MMA (MMA = methyl methacrylate) for the formation of the syndio-enriched PMMAs.Figure optionsDownload full-size imageDownload as PowerPoint slide