The Role of Nitrogen Donors in Zinc Catalysts for Lactide Ring-Opening Polymerization

Abstract

The electronic effects of nitrogen donors in zinc catalysts for ring-opening polymerization of cyclic esters were investigated. Alkyl and benzyloxy zinc complexes supported by tridentate diamino- and aminoimino phenolate ligands were synthesized, and their solid-state and solution structures characterized. The solution-state structures showed that the alkyl complexes are mononuclear, while the alkoxy complexes are dimeric with the ligands coordinated with different denticities depending on the nature of the ligand donors. The catalytic activities of these compounds toward the ring-opening polymerization of racemic lactide were studied and showed that catalysts with secondary and imine nitrogen donors are more active than analogues with tertiary amines.

A Combined Approach using Sonochemistry and Photocatalysis: How to Apply Sonophotocatalysis for Biomass Conversion?

“…The synergistic combination of sonocatalysis and photocatalysis, called "sonophotocatalysis"o r" photosonocatalysis" (Figure 1) depending on the focus of the author, has been reported in the literature, especially for the degradation of organic compoundsi nt he aqueous phase, [42][43][44] such as phenol and phenolic compounds, [45,46] 2-propanol, [47] naphthol blue black, [48] methylene blue, [49] reactive red 120, [50] methyl orange, [51] hydrogels, [52] textile industrial effluents, [53] pesticides from waste-water, [54] paracetamol, [55] etc.…”

Towards New Robust Zn(II) Complexes for the Ring‐Opening Polymerization of Lactide Under Industrially Relevant Conditions

“…developed various zinc complexes with β‐diiminates as ligand . Zinc aminophenolates from Ma et al ., Mehrkhodavandi et al ., Tolman et al . showed high activities and stereoselectivities.…”

“…Thus, Coates et al developed various zinc complexes with β-diiminates as ligand. [9] Zinc aminophenolates from Ma et al, [10] Mehrkhodavandi et al, [11] Tolman et al [12] showed high activities and stereoselectivities. Hayes and Wheaton et al developed zinc complexes bearing phosphinimines [13] and Schulz et al [14] zinc ketoiminate and βdiketiminate complexes.…”

Synthesis, Structures, and Catalytic Activity of Homo‐ and Heteroleptic Ketoiminate Zinc Complexes in Lactide Polymerization

“…[10a] In addition to β‐diketiminate complexes, ketoiminate zinc complexes have also been explored in lactide polymerization and the influence of both steric and electronic variations of the N ‐substituents on the catalytic activity was demonstrated . Moreover, the catalytic activity of zinc complexes supported by tridentate N , N′ , O ‐chelating diamino‐ and aminoiminophenolate ligands was shown to depend on the nature of the central N‐donor function, since tertiary amines were less active compared to complexes containing a central secondary amine or imine group …”