Reactivity of zinc halide complexes containing camphor-derived guanidine ligands with technical rac-lactide

Angela Metz, Joshua Heck, Clara Marie Gohlke, Konstantin Kröckert, Yannik Louven, Paul McKeown, Alexander Hoffmann, Matthew D. Jones, Sonja Herres-Pawlis

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Three new zinc complexes with monoamine-guanidine hybridligands have been prepared, characterized by X-ray crystallography and NMR spectroscopy, and tested in the solvent-free ring-opening polymerization of rac-lactide. Initially the ligands were synthesized from camphoric acid to obtain TMGca and DMEGca and then reacted with zinc(II) halides to form zinc complexes. All complexes have a distorted tetrahedral coordination. They were utilized as catalysts in the solvent-free polymerization of technical rac-lactide at 150 °C. Colorless polylactide (PLA) can be produced and after 2 h conversion up to 60% was reached. Furthermore, one zinc chlorido complex was tested with different qualities of lactide (technical and recrystallized) and with/without the addition of benzyl alcohol as a co-initiator. The kinetics were monitored by in situ FT-IR or 1H NMR spectroscopy. All kinetic measurements show first-order behavior with respect to lactide. The influence of the chiral complexes on the stereocontrol of PLA was examined. Moreover, with MALDI-ToF measurements the end-group of the obtained polymer was determined. DFT and NBO calculations give further insight into the coordination properties. All in all, these systems are robust against impurities and water in the lactide monomer and show great catalytic activity in the ROP of lactide.

Original languageEnglish
Article number85
JournalInorganics
Volume5
Issue number4
DOIs
Publication statusPublished - 30 Nov 2017

Fingerprint

Camphor
Guanidine
Zinc
Ligands
Nuclear magnetic resonance spectroscopy
Benzyl Alcohol
Kinetics
X ray crystallography
Ring opening polymerization
Discrete Fourier transforms
dilactide
Catalyst activity
Polymers
Monomers
Polymerization
Impurities
Catalysts
Acids
Water

Keywords

  • Guanidine
  • Polylactide
  • Ring-opening polymerization
  • Zinc

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Reactivity of zinc halide complexes containing camphor-derived guanidine ligands with technical rac-lactide. / Metz, Angela; Heck, Joshua; Gohlke, Clara Marie; Kröckert, Konstantin; Louven, Yannik; McKeown, Paul; Hoffmann, Alexander; Jones, Matthew D.; Herres-Pawlis, Sonja.

In: Inorganics, Vol. 5, No. 4, 85, 30.11.2017.

Research output: Contribution to journalArticle

Metz, Angela ; Heck, Joshua ; Gohlke, Clara Marie ; Kröckert, Konstantin ; Louven, Yannik ; McKeown, Paul ; Hoffmann, Alexander ; Jones, Matthew D. ; Herres-Pawlis, Sonja. / Reactivity of zinc halide complexes containing camphor-derived guanidine ligands with technical rac-lactide. In: Inorganics. 2017 ; Vol. 5, No. 4.
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