Rare-earth metal complexes derived from the acids Ph2C(X)CO2H (X= OH, NH2): Structural and ring opening polymerization (ROP) studies.

Collins, Jack; Santoro, Orlando; Prior, Timothy J.; Chen, Kai; Redshaw, Carl

Abstract

Treatment of Ln(NO3)3.6H2O (Ln = La, Ce) with an equimolar amount of 2,2’-diphenylglycine (DpgH) in ethanol afforded the corresponding hexacoordinated complexes (DpgH±)3Ln(NO3)3.H2O (DpgH± = zwitterionic 2,2’-diphenylglycine, Ln = La (1), Ce (2)). The spectroscopic and structural features of these compounds have been investigated. Similar reactions with the related benzilic acid (BenzH2) were unsuccessful. The catalytic behaviour of 1 and 2 in the homo- and copolymerization of epsilon-caprolactone (epsilon-CL) and rac-lactide (r-LA) has been investigated herein. In the case of epsilon-CL, the two complexes exhibited comparable activity, allowing for complete monomer conversion under aerobic and solvent-free conditions at 150 °C in 24 h. With respect to the ROP of r-LA, 1 was found to be completely inactive, while only 8% conversion was achieved in the presence of 2. Liquid oligomers were isolated during epsilon-CL/r-LA co-polymerization in the presence of both complexes. The catalytic activity of the pre-ligands DpgH and BenzH2 (i.e. metal-free) was also examined. Interestingly, only BenzH2 was found to be active, although it required a higher catalyst loading and the presence of benzyl alcohol as co-activator.

Citation

Collins, J., Santoro, O., Prior, T. J., Chen, K., & Redshaw, C. (2021). Rare-earth metal complexes derived from the acids Ph2C(X)CO2H (X= OH, NH2): Structural and ring opening polymerization (ROP) studies. Journal of molecular structure, 1224, Article 129083. https://doi.org/10.1016/j.molstruc.2020.129083

• Journal Article Type: Article
• Acceptance Date: Aug 12, 2020
• Online Publication Date: Aug 13, 2020
• Publication Date: Jan 15, 2021
• Deposit Date: Aug 13, 2020
• Publicly Available Date: Aug 14, 2021
• Journal: Journal of Molecular Structure
• Print ISSN: 0022-2860
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 1224
• Article Number: 129083
• DOI: https://doi.org/10.1016/j.molstruc.2020.129083
• Keywords: Lanthanide; Magic Acids; Diphenylglycine; Ring Opening Polymerization; Biodegradable
• Public URL: https://hull-repository.worktribe.com/output/3557437
• Publisher URL: https://www.sciencedirect.com/science/article/abs/pii/S0022286020314058?via%3Dihub