Synthesis, characterization and catalytic activity of lithium and sodium iminophenoxide complexes towards ring-opening polymerization of l-lactide

Abstract

A series of lithium and sodium iminophenoxide complexes have been successfully synthesized and characterized by X-ray crystallography and investigated as catalysts for the ring opening polymerization of L-lactide. The nature and steric bulk of the ligands coordinated to the central metal ions greatly influence the catalytic properties. Complexes with bidenate ligands exhibit higher catalytic activity than tridentate counterparts because the third coordination atom contends with L-lactide, which decreases activity. Oxygen is the third atom in the tridentate ligand, providing stronger chelation ability with Li and Na than nitrogen or sulfur and occupies the space with which L-lactide is coordinated.

Ring‐opening polymerization of lactide, ε‐caprolactone and their copolymerization catalyzed by β‐diketiminate zinc complexes

“…Up to date, a variety of well‐defined metal complexes capable of initiating the ROP of the related cyclic esters have been reported [1b‐k]. Among them, complexes of groups 1 and 2 metals as well as zinc have attracted great interests due to the low toxicity of the elements and the good control of the complexes over the polymerization processes. As an environmental friendly metal, zinc has relatively less ionic nature when compared to groups 1 and 2 metals, and the filled d orbitals when it is in the normal oxidation state of Zn(II) also allow lower coordination numbers; both of these features are especially beneficial to the construction of well‐defined zinc complexes.…”

Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

“…Recent research efforts have been directed toward the search of less toxic-or more biocompatible-metal-based initiators [66]. Li and Na complexes bearing imino-phenoxide ligands, for example, have also been synthetized and used for the L-lactide polymerization [67]. Although the research area is flourishing, further studies need to be carried out in the near future before the materials could be commercialized and used in biomedical applications.…”

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

“…In 2012, Chen et al prepared 12 novel tetrametallic Li-and Na-complexes (six each) by treating pro-ligands 1-6 with LiO t Bu or NaH in THF (Scheme 1) [22]. All compounds were tested as catalysts in the ROP of L-lactide in the presence of benzyl alcohol (BnOH) as co-activator in THF ( Table 1).…”