Simple is best: Diamine zinc complexes as unexpected catalysts in lactide polymerisation

A series of monomeric coordination compounds containing zinc(II) chloride or zinc(II) bromide and the 1,2-diamine ligands TMEDA, TEEDA, (R,R)-TMCDA, (R,R)-TECDA and cis-TMCDA have been synthesised and structurally characterised using X-ray diffraction analysis. All but one complex could be successfully used as initiators for the solvent-free ring-opening polymerisation of d,l-lactide. In particular, the polylactide (PLA) prepared with compounds containing (R,R)-TECDA is obtainable in high yields with molecular weights suitable for industrial applications. Thus a class of stable, easy to synthesise and efficient PLA catalysts with neutral ligands is introduced.

A series of monomeric coordination compounds containing zinc(II) chloride or zinc(II) bromide and the 1,2-diamine ligands TEEDA, (R,R)-TMCDA, (R,R)-TECDA and cis-TMCDA were synthesised, structurally characterised and could be successfully used as highly stable initiators for the solvent-free ring-opening polymerisation of d,l-lactide.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis and structural characterisation of six diamine-zinc complexes.
► Unexpected reactivity in ring-opening polymerisation of lactide.
► Great robustness against industrial conditions of lactide polymerisation.
► Low-priced starting materials for green polymerisation chemistry.