Tuning a robust system: N,O Zinc Guanidine Catalysts for the ROP of Lactide

Pascal M Schäfer, Paul McKeown, Martin Fuchs, Ruth Rittinghaus, Alina Hermann, Johanna Henkel, Sebastian Seidl, Christopher Roitzheim, Agnieszka Ksiazkiewicz, Alexander Hoffmann, Andrij Pich, Matthew Jones, Sonja Herres-Pawlis

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Abstract

Non-toxic, highly-active and robust complexes are the holy grail as ideal green catalysts for the polymerisation of biobased and biodegrable polylactide. Four new zinc guanidine complexes [ZnCl2(TMG4NMe2asme)], [ZnCl2(TMG5Clasme)], [ZnCl2(TMG5Measme)] and [ZnCl2(TMG5NMe2asme)] with different electron-donating and electron-withdrawing groups on aromatic backbone of the ligand have been synthesised. Ligands are derived from low-cost commercially available compounds and have been converted in a three- or four-step synthesis into the desired ligand in good yields. The compounds have been fully characterised and tested in the ROP of rac-LA in the melt under industrially relevant conditions. The complexes are based on the recently published structure [ZnCl2(TMGasme)] which has shown high activity in the polymerisation of lactide at 150 °C. Different substituents in the para-position to the guanidine moiety significantly increase the polymerisation rate whereas positioning substituents in meta-position causes no change in the reaction rate. With molecular weights over 71 000 g mol-1, the best catalyst produces polymer for several industrial applications and its polymerisation rate approaches the one of Sn(Oct)2. The robust systems are able to polymerise non-purified lactide. The initiation of the polymerisation is suggested to occur by impurities in the monomer.
Original languageEnglish
Pages (from-to)6071-6082
Number of pages12
JournalDalton Transactions
Volume48
Issue number18
Early online date29 Jan 2019
DOIs
Publication statusPublished - 14 May 2019

ASJC Scopus subject areas

  • Inorganic Chemistry

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    Schäfer, P. M., McKeown, P., Fuchs, M., Rittinghaus, R., Hermann, A., Henkel, J., Seidl, S., Roitzheim, C., Ksiazkiewicz, A., Hoffmann, A., Pich, A., Jones, M., & Herres-Pawlis, S. (2019). Tuning a robust system: N,O Zinc Guanidine Catalysts for the ROP of Lactide. Dalton Transactions , 48(18), 6071-6082. https://doi.org/10.1039/C8DT04938F