Herein, we report the preparation and characterisation of iron(III) salalen complexes, with variation of ligand substituents and backbone investigated. Six new complexes were prepared and characterised by elemental analysis, mass spectrometry and X-ray crystallography. These complexes have been applied for the ring opening polymerisation (ROP) of rac-lactide

A series of Mg(ii) and Zn(ii) catalen complexes have been prepared for PLA formation and recycling.

Cracking the whip: Simple iron(iii) acetate complexes have been applied to the catalytic cyclic carbonate formation and lactide ROP.

A series of five iron and aluminum complexes bearing {ONSO} imine thiobis(phenolate) ligands have been prepared and applied to the ROP of rac-lactide. Fe(1)Cl produced PLA 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 1 H{ 1 H} NMR, 13 C{ 1 H} NMR, GPC, TGA, DSC and pXRD. 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 2 (Ð = 1.04-1.12) and moderate isotactic preference (Pm = 0.56-0.72), with polymerization outcome correlating with ligand substituents.

A comprehensive range of 14 synthetically simple, air-stable, and structurally diverse Fe­(III) complexes, comprising salalen, salen, salan, and thiolen frameworks, were applied as catalysts to the ring-opening copolymerization (ROCOP) of phthalic anhydride (PA) and cyclohexene oxide (CHO) without the need for extra additives, such as co-catalysts, as part of a newly discovered unary system. Alternating poly­(1,2-cyclohexylene-1,2-phthalate) {poly­(CHO-co-PA)} was obtained with reasonable molecular weight, narrow dispersity, and high % ester linkage. Structure–activity relationships have been investigated and discussed. The most interesting discovery was that while performing “ligand control” ROCOP experiments (highlighting the importance of such checks in catalysis), all these organocatalysts outperformed their Lewis acidic Fe­(III) analogues; these results are significant as a simplistic, metal- and halide-free, organocatalytic single-component approach to ROCOP was developed. There are few examples of organocatalysts in the literature, tending to rely on two component systems with harsher, air-sensitive chemicals, and these results provide hope that more reactive, effective systems are possible in an area very much in its infancy but will no doubt emerge and potentially prove vital to future sustainable polymerization research. Thermal properties were accessed via differential scanning calorimetry analysis, and for the amorphous copolymers, the T g values ranged by 35 °C from 100 °C to a respectable 135 °C.

Nine new complexes based on thioether appended iminophenolate (ONS) ligands have been prepared and fully characterized in solution by NMR spectroscopy.

A range of Fe(iii)-salalen and -thiolen–chloride complexes have been prepared and are shown to be active catalysts for the selective coupling of CO2 and cyclohexene oxide (CHO).