Lactide polymerization using a sterically encumbered, flexible zinc complex.

Citation metadata

Date: Apr. 2022
From: Canadian Journal of Chemistry(Vol. 100, Issue 4)
Publisher: NRC Research Press
Document Type: Report
Length: 5,010 words
Lexile Measure: 1660L

Document controls

Main content

Abstract :

4-(tert-Butyl)-2-trityl-6-(di-(2-picolyl)amine)phenol, LH, was prepared from paraformaldehyde, 4-(tert-butyl)-2-tritylphenol, and di-(2-picolyl)amine. Reaction with Zn(N([SiMe.sub.3]).sub.2]).sub.2] gave LZnN[SiMe.sub.3]).sub.2]. The complex was shown by X-ray diffraction study, variable temperature NMR, and DFT calculations to coordinate only one pyridine ligand, which allows for fast and facile complex isomerisation. LZnN[SiMe.sub.3]).sub.2] was active in rac-lactide polymerization, but in contrast to previous complexes of this type, it did not show any evidence for isotactic monomer enchainment via a catalytic-site mediated chain-end control mechanism. Addition of alcohol led to increased activity, but the complex was unstable in the presence of free alcohol. Key words: zinc complexes, lactide polymerization, isotacticity, stereocontrol, reaction mechanism, catalysis, inorganic chemistry. Nous avons prepare le ligand 4-(tert-butyl)-2-trityl-6-(di-(2-picolyl)amine)phenol, designe comme LH, a partir du paraformaldehyde, du 4-(tert-butyl)-2-tritylphenol et de la di-(2-picolyl)amine. La reaction avec le Zn(N([SiMe.sub.3]).sub.2]).sub.2] a produit le complexe LZnN[SiMe.sub.3]).sub.2]. Par des methodes de diffraction des rayons X, de RMN a temperature variable et de calculs DFT, nous avons montre que le complexe coordonne un seul ligand pyridine, ce qui permet une isomerisation rapide et facile du complexe. Le complexe LZnN[SiMe.sub.3]).sub.2] etait actif en polymerisation du rac-lactide, mais contrairement aux complexes anterieurs de ce type, il n'a montre aucun signe d'enchainement isotactique des monomeres passant par un mecanisme de controle de terminaison de chaine medie par un site catalytique. L'ajout d'alcool a entraine une augmentation de l'activite, mais le complexe etait instable en presence d'alcool libre. [Traduit par la Redaction] Mots-cles : complexes de zinc, polymerisation du lactide, isotacticite, controle de la stereoselectivite, mecanisme de reaction, catalyse, chimie inorganique.

Source Citation

Source Citation   

Gale Document Number: GALE|A700235416