Synthesis, characterisation and X-ray structure of Cu(II) and Zn(II) complexes bearing N,N-dimethylethylenamine-camphorylimine ligands: Application in the polymerisation of rac-lactide

Abstract

We have synthesised the novel Cu(II) and Zn(II) complexes (CDM)CuCl2 and (CDM)ZnCl2, where CDM is (E)-N1,N1-dimethyl-N2-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)ethane-1,2-diamine. X-ray diffraction analysis revealed that the geometry around the Zn(II) centre can be best described as a distorted tetrahedron. In the Cu(II) complex, the bulk of camphor ligand suppresses the square planar geometry; the complex thus has a highly distorted square planar and distorted tetrahedral geometry. Alkoxy derivatives generated in situ proved to be highly efficient catalysts for the ring-opening polymerisation (ROP) of rac-lactide (rac-LA), yielding polylactide (PLA) with narrow polydispersity indexes (PDIs). (CDM)Cu(OCHMe2)2 exhibited a high activity for stereoselective ROP of rac-LA, with complete conversion within 2min, producing heterotactic-enriched PLA (Pr=0.85).