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Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability

Zhang, Xin; Chen, Kai; Chicoma, Melissa; Goins, Kimberly; Prior, Timothy J.; Nile, Terence A.; Redshaw, Carl

Authors

Xin Zhang

Kai Chen

Melissa Chicoma

Kimberly Goins

Terence A. Nile

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Professor Carl Redshaw C.Redshaw@hull.ac.uk
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry



Abstract

The Schiff-base compounds 2,4-di-tert-butyl-6-(((3,4,5-trimethoxyphenyl)imino)methyl)phenol (L1H), 2,4-di-tert-butyl-6-(((2,4,6-trimethoxyphenyl)imino)methyl)phenol (L2H), 2,4-di-tert-butyl-6-(((2,4-trimethoxyphenyl)imino)methyl)phenol) (L3H) derived from anilines bearing methoxy substituents have been employed in the preparation of alkylaluminum and zinc complexes. Molecular structure determinations reveal mono-chelate aluminum complexes of the type [Al(Ln)(Me)2] (L1, 1; L2, 2; L3, 3), and bis(chelate) complexes for zinc, namely [Zn(Ln)2] (L1, 5; L2, 6; L3, 7). All complexes have significant activity at 50 °C and higher activity at 100 °C for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) with good control over the molar mass distribution (Mw/Mn < 2) and molecular weight. Complex 1 was found to be the most active catalyst, achieving 99% conversion within 18 h at 50 °C and giving polycaprolactone with high molecular weight; results are compared against aniline-derived (i.e., non-methoxy containing) complexes (4 and 8). Aluminum or zinc complexes derived from L1 exhibit higher activity as compared with complexes derived from L2 and L3. Complex 1 was also tested as an initiator for the copolymerization of ε-CL and glycolide (GL). The CL-GL copolymers have various microstructures depending on the feed ratio. The crosslinker 4,4′-bioxepane-7,7′-dione was used in the polymerization with ε-CL using 1, and well-defined cross-linked PCL was afforded of high molecular weight.

Citation

Zhang, X., Chen, K., Chicoma, M., Goins, K., Prior, T. J., Nile, T. A., & Redshaw, C. (2021). Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability. Catalysts, 11(9), https://doi.org/10.3390/catal11091090

Journal Article Type Article
Acceptance Date Sep 3, 2021
Online Publication Date Sep 9, 2021
Publication Date Sep 9, 2021
Deposit Date Sep 10, 2021
Publicly Available Date Sep 10, 2021
Journal Catalysts
Print ISSN 2073-4344
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 11
Issue 9
Article Number 1090
DOI https://doi.org/10.3390/catal11091090
Keywords Schiff base; Organoaluminum; Zinc; Catalyst; Polycaprolactone; Copolymer; Ring-opening polymerization; Molecular structures
Public URL https://hull-repository.worktribe.com/output/3834316

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Copyright Statement
Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).



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