Synthesis and characterization of bisphenol sodium complexes: An efficient catalyst for the ring-opening polymerization of l-lactide

Structural subtleties and catalytic activity of sodium aminophenolate complexes in polylactide degradation: towards sustainable waste management solutions

This study explores the intricate coordination chemistry of sodium aminophenolate species and their significant role in the depolymerization of polylactide (PLA), offering novel insights into catalytic degradation processes. By examining sodium coordination entities, including dimers and larger aggregates such as tetramers, we reveal how structural modifications, particularly the manipulation of steric hindrances, influence the formation and stability of these complexes. The dimers, characterized by a unique four-center core (Na-O-Na-O), serve as a foundational motif, which is further elaborated to obtain complexes with varied coordination environments through strategic ligand design. Our research delves into the lability of the amino arm in these complexes, a critical factor that facilitates the coordination of PLA to the sodium center, thereby initiating the depolymerization process. Moreover, DFT studies have been pivotal in identifying the most energetically favorable structures for catalysis, highlighting a distinct preference for an eight-membered ring motif stabilized by intramolecular hydrogen bonds. This motif not only enhances the catalyst's efficiency but also introduces a novel structural paradigm for sodium-based catalysis in PLA degradation. Experimental validation of the theoretical models was achieved through NMR spectroscopy, which confirmed the formation of the active catalyst forms and monitored the progress of PLA degradation. The study presents a comprehensive analysis of the influence of ligand structure on the catalytic activity, underscoring the importance of the eight-membered ring motif. Furthermore, we demonstrate how varying the steric bulk of substituents on the amino arm affects the catalyst's performance, with benzyl-substituted ligands exhibiting superior activity. Our findings offer a profound understanding of the structural factors governing the catalytic efficiency of sodium aminophenolate complexes in PLA degradation. This research not only advances the field of coordination chemistry but also presents a promising avenue for the development of efficient and environmentally friendly catalysts for polymer degradation.

Scrabbling around in Synthetic Nuances Managing Sodium Compounds: Bisphenol/Bisnaphthol Synthesis by Hydroxyl Group Masking

A unique method of bisphenol/bisnaphthol synthesis is being proposed, serendipitously discovered in the course of the careful analysis of an aminophenol methylation reaction. The insightful exploration of the synthesis of N- or O-methylated species, originating from functionalized phenols obtained by a conventional strategy, provided the opportunity to discover an unexpected reaction pathway yielding various bisphenols. Sodium complexes were found to be crucial intermediates in the synthetic scenario. Their formation, which is usually an imperceptive step, was substantial for the productive outcome of functional group protection. Thorough exploration revealed an essential structural motif of aminophenolate, necessary for the successful outcome of the reaction, and also enabled establishing the limitations of the new method. The work demonstrated that a slight change in the perspective and close inspection of the synthetic nuances can answer the important question concerning what a specific target-oriented synthesis strategy is lacking.

The protection of the hydroxyl group of aminophenols with use of MeI—a general and, in many cases, excellent methylation reagent—was investigated. In-depth understanding of the mechanistic aspects of methyl protective group incorporation provided a practical guide for its application in organic synthesis, but it also opened a new route for the synthesis of an original group of bisphenols.

Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of rac-lactide

Compounds of Li, Na, K and Ca of a tetradentate amino-bis(phenolato) ligand were prepared. Bimetallic compounds formulated as M₂[L](THF)_n (where M = Na, n = 1 (1·THF) or Li, n = 1 (2·THF)) were synthesized via the reaction of H₂[L] (where [L] = 2-pyridylmethylamino-N,N-bis(2-methylene-4-methoxy-6-tert-butylphenolato) with sodium hydride or n-butyllithium, respectively, in THF. Monometallic complexes MH[L](THF)_n (where M = Na, n = 1 (3·THF), Li, n = 0 (4) and K, n = 0 (5)) were obtained by reaction of H₂[L] with MN(SiMe₃)₂ where M = Na, Li, or K. Calcium complex Ca[L](THF) (6·THF) was synthesized in two ways; reaction of Na₂[L] with calcium iodide in THF, and reaction of Ca[N(SiMe₃)₂]₂ with H₂[L] in toluene. Compounds 1-6 exhibit activity for rac-lactide polymerization under melt and solution conditions. Moderate control of polymer molecular weights was achieved in toluene, whereas polydisperse polymer was obtained under solvent free conditions. MALDI-TOF MS analysis of the polymer end groups revealed a predominantly cyclic nature for the polylactides.

Synthesis, characterization, and catalytic activity of sodium ketminiate complexes toward the ring-opening polymerization of l-lactide

Na complexes bearing ketiminate ligands revealed the greater catalytic activity and polymer controllability than that of Na complexes bearing Schiff base ligands.

Vanadium(v) phenolate complexes for ring opening homo- and co-polymerisation of ε-caprolactone, l-lactide and rac-lactide

Vanadium(v) di-, tri- and tetra-phenolate complexes have been screened for their ability to ring open homo- (and co-) polymerise ε-caprolactone, l-lactide and rac-lactide.

Gallium and indium complexes containing the bis(imino)phenoxide ligand: synthesis, structural characterization and polymerization studies

A series of gallium and indium complexes containing the bis(imino)phenolate ligand framework were synthesized and completely characterized with different spectroscopic techniques.

Ring-opening polymerization of rac-lactide mediated by tetrametallic lithium and sodium diamino-bis(phenolate) complexes

Sodium complex contains interesting intramolecular η⁶-arene interaction and shows excellent catalytic behaviour for polymerization of lactide.