Tuning the thiolen: Al(III) and Fe(III) thiolen complexes for the isoselective ROP of rac-lactide

A series of five iron and aluminum complexes bearing {ONSO} imine thiobis(phenolate) ligands have been prepared and applied to the ring-opening polymerization (ROP) of rac-lactide. Fe(1)Cl produced polylactide with a very strong isotactic bias (Pm = 0.79–0.89) and well-defined melting temperatures (Tm = 154–181 °C). The polymers have been characterized by a combination of 1H{1H} NMR, 13C{1H} NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and powder X-ray diffraction. Fe(1)Cl has also been shown to activate CO2, at atmospheric pressure and concentrations, to form a carbonato-bridged dimer. Fe(2–5)Cl and Al(1–5)Me were also active for lactide ROP demonstrating good-molecular-weight control (Đ = 1.04–1.12) and moderate isotactic preference (Pm = 0.56–0.72), with polymerization outcome correlating with ligand substituents

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

This review describes the recent advances (from 2008 onwards) in the use of Schiff-base metal complexes as catalysts for the ring opening polymerization (ROP) of cyclic esters. The synthesis and structure of the metal complexes, as well as all aspects concerning the polymerization process and the characteristics of the polymers formed, will be discussed

Aluminum complexes of mono-pyrrolidine ligands for the con-trolled ring opening polymerization of lactide

In this paper we report the full characterization (solution-state NMR spectroscopy and solid-state structures) of a series of Al­(III) half-salan complexes and their exploitation for the ring-opening polymerization of <i>rac</i>-lactide. Depending on the ligand employed and stoichiometry of the complexation, structures of the form Al­(<b>X</b>)₂Me or Al­(<b>X</b>)­Me₂ were isolated. Interestingly Al­(<b>2</b>)₂Me and Al­(<b>2</b>)­Me₂ produce PLA with a strong isotactic bias (<i>P</i>_m up to 0.80), whereas all other complexes produced atactic PLA. This is in contrast to recent studies on similar salan ligand systems. PLAs with predictable molecular weights and narrow distributions were achieved. The results are discussed in terms of steric and electronic properties of the ligands