Efficient ring-opening polymerization (ROP) of ϵ-caprolactone catalysed by isomeric pyridyl β-diketonate iron(III) complexes

Sze Ling Lee, Fei Long Hu, Xiu Juan Shang, Yi Xiang Shi, Ai Ling Tan, Jens Mizera, Jack K. Clegg, Wen Hua Zhang, David J. Young, Jian Ping Lang

Research output: Contribution to journalArticle

Abstract

A series of Fe(iii) complexes of β-diketonate ligands, 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L1), 1-(2-pyridyl)-3-(2-pyridyl)-1,3-propanedione (L2), 1-(2-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L3), 1-(3-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L4), 1-(3-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L5) and 1-(4-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L6), viz. [Fe(L1)3] (1), [Fe(L2)3] (2), [Fe(L3)3] (3), [Fe(L4)3] (4), [Fe(L5)3] (5) and [Fe(L6)3] (6) have been structurally characterized. All but one complex (1) catalyzed the ring-opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL) in near quantitative yield at 110 °C to give polymers with relatively narrow polydispersities (PDI). The comparison of in situ reaction and a reaction with preformed 1 indicated that the latter was a better catalyst, giving a higher molecular weight. Complex 2 catalyzed this reaction in a more modest yield reflecting its greater thermal stability, shorter Fe-O bonds and minimal distortion in fold angle among the isomeric complexes, suggesting that ligand dissociation is important for catalytic activity.

Original languageEnglish
Pages (from-to)14457-14465
Number of pages9
JournalNew Journal of Chemistry
Volume41
Issue number23
DOIs
Publication statusPublished - 7 Dec 2017
Externally publishedYes

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    Lee, S. L., Hu, F. L., Shang, X. J., Shi, Y. X., Tan, A. L., Mizera, J., Clegg, J. K., Zhang, W. H., Young, D. J., & Lang, J. P. (2017). Efficient ring-opening polymerization (ROP) of ϵ-caprolactone catalysed by isomeric pyridyl β-diketonate iron(III) complexes. New Journal of Chemistry, 41(23), 14457-14465. https://doi.org/10.1039/c7nj03571c