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

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), Article 1090. https://doi.org/10.3390/catal11091090

• Journal Article Type: Article
• Acceptance Date: Sep 3, 2021
• Online Publication Date: Sep 9, 2021
• Publication Date: Sep 1, 2021
• Deposit Date: Sep 10, 2021
• Publicly Available Date: Sep 10, 2021
• Journal: Catalysts
• Print ISSN: 2073-4344
• Electronic 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