Ring-Opening Copolymerization Using Simple Fe(III) Complexes and Metal- and Halide-Free Organic Catalysts

Abstract

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.

Perfectly Alternating Copolymerization of Cyclic Anhydrides and Epoxides with Yttrium β-Diketiminate Complexes

“…Additionally, the polymer molecular weights were much lower than expected for the single chloride initiator at short reaction times, which could be sensitivity to trace moisture in the epoxide. A prior study identified that protonated ligands were more active than the corresponding metal complexes with the ligands coordinated . A combination of the protonated ligand of 1 and [PPN]Cl showed similar side reactions to [PPN]Cl alone.…”

“…A prior study identified that protonated ligands were more active than the corresponding metal complexes with the ligands coordinated. 33 A combination of the protonated ligand of 1 and [PPN]Cl showed similar side reactions to [PPN]Cl alone. However, the molecular weight of the polymer suggested the ligand as an initiating species for polymerization, since the molecular weight was less than half that for [PPN]Cl alone.…”

Polyether/Polythioether Synthesis via Ring-Opening Polymerization of Epoxides and Episulfides Catalyzed by Alkali Metal Carboxylates

“…The MALDI-TOF MS of the obtained products confirmed the expected BDM-initiated polyethers structure and also revealed the presence of water-initiated species (Figures S14–S19). The water-initiated species was ascribed to the contamination of monomers with small amounts of water or monomer-derived glycol, the removal of which is very difficult and typically requires multiple distillations. , Notably, the carboxylate-initiated polymerization and chain transfer were suppressed in the ROP of all monomers, as evidenced by the related MALDI-TOF MS.…”

“…The water-initiated species was ascribed to the contamination of monomers with small amounts of water or monomer-derived glycol, the removal of which is very difficult and typically requires multiple distillations. 32,33 Notably, the carboxylate-initiated polymerization and chain transfer were suppressed in the ROP of all monomers, as evidenced by the related MALDI-TOF MS.…”

New mixed‐ligand iron(III) complexes containing thiocarbohydrazones: Preparation, characterization, and chemical reactivity analysis through theoretical calculations

“…[ 26–28 ] Especially iron complexes emerge as up‐and‐coming catalysts as a result of the relatively low toxicity and price of iron. [ 29–32 ] Mixed ligand complexes play a key role in biological chemistry because mixed chelation commonly occurs in biological fluids. [ 33–35 ] Synthesis and characterization of mixed ligand complexes are gaining importance day by day.…”