Stereoselective polymerisation of rac-lactide catalysed by Cu(II) complexes bearing chloro derivatives of N,N′-bis(benzyl)dimethyl-(R,R)-1,2-diaminocyclohexane

The novel Cu(II) complexes Cu(L1)Cl2, Cu(L2)Cl2, and Cu(L3)Cl2, where L1 is N,N′-bis(benzyl)dimethyl-(R,R)-1,2-diaminocyclohexane, L2 is N,N’-bis(o-chlorobenzyl)dimethyl-(R,R)-1,2-diaminocyclohexane, and L3 is N,N′-bis(p-chlorobenzyl)dimethyl-(R,R)-1,2-diaminocyclohexane, were synthesised and structurally characterised using X-ray diffraction. The structures were mononuclear with Cu(II) atoms in distorted square planar geometries. The alkoxy derivatives of the dichloro Cu(II) rapidly polymerised rac-lactide (rac-LA) (<1 min for complete conversion) with good average molecular weights (Mn), and narrow polydispersities. Additionally, heterotactic-enriched polylactides (PLAs) had a Pr of up to 0.88. Notably, the substituents on the benzyl moieties of the (R,R)-1,2-diaminocyclohexane fragments affected the stereoselectivities of the PLAs.

Graphical abstractDiisopropoxide derivatives generated in situ, of novel enantiopure dichloro Cu(II) supported by N,N’-bis(benzyl)dimethyl-(R,R)-1,2-diaminocyclohexane derivatives rapidly polymerised rac-lactide (rac-LA) (<1 min for complete conversion) with good average molecular weights (Mn), and narrow polydispersities. Additionally, heterotactic-enriched polylactides (PLAs) had a Pr of up to 0.88.Figure optionsDownload full-size imageDownload as PowerPoint slide