Mononuclear salen-gallium complexes for iso-selective ring-opening polymerization (ROP) of: Rac -lactide

David Specklin, Christophe Fliedel, Frédéric Hild, Samir Mameri, Lydia Karmazin, Corinne Bailly, Samuel Dagorne

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A series of mononuclear salen-supported gallium amido/alkoxide derivatives were prepared and structurally characterized and subsequently used as initiators in rac-lactide ring-opening polymerisation (ROP). The reaction of variously substituted salen ligands (1a-1f) with 0.5 equiv. of Ga2(NMe2)6 allowed the isolation of the corresponding (salen)Ga-NMe2 chelates (2b-2d, 2f) via an amine elimination route, as poorly soluble compounds in common solvents. The (salen)Ga-OBn derivatives (3a-3e) may be readily accessed by an amine-elimination/alcoholysis sequence and the molecular structures of 3a, 3d and 3e were confirmed through X-ray crystallography diffraction analysis. The present (salen)Ga-X species may effectively mediate the iso-selective ROP of rac-LA in a controlled manner (Pm up to 0.77 using a 1/1 2f/BnOH mixture as ROP initiator), with a ROP activity greatly dependent upon steric hindrance and geometrical constraints imposed by the variously substituted salen ligands. Based on the present study, salen ligands with limited steric hindrance and a certain degree of flexibility appear best suited for iso-selective ROP by (salen)Ga chelates. The salen-gallium complex 3a is also effective for the controlled ROP of ϵ-caprolactone (CL) and the production of PCL-b-PLA copolymers.

Original languageEnglish
Pages (from-to)12824-12834
Number of pages11
JournalDalton Transactions
Volume46
Issue number38
DOIs
Publication statusPublished - 1 Jan 2017

Keywords

  • Chelation
  • Chemical reactions
  • Crystallography
  • Gallium
  • Polymerization

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