Catalytic Formation of Cyclic Carbonates using Gallium Aminotrisphenolate Compounds and Comparison to their Aluminium Congeners: A Combined Experimental and Computational Study

Abstract: This work reports on the use of gallium aminotrisphenolate compounds as catalysts for the synthesis of cyclic carbonates from epoxides and CO2. The results show that they are highly active, and more so than the corresponding aluminium congeners. The catalyst system is applicable at low and elevated temperatures across a wide substrate scope including terminal, internal, multiple and fully deuterated epoxides. Applying low catalyst loadings has allowed for a TON of 344,000 to be obtained, highlighting their stability. A DFT investigation has confirmed that the gallium catalysts have lower energetic profiles compared to the aluminium congeners. Measurement of the Lewis acidity of both the gallium and aluminium aminotrisphenolate compounds using the Gutmann‐Beckett method provides the experimental proof that the gallium compounds are more Lewis acidic than their aluminium congeners. Finally, Ab‐Initio Molecular Dynamic (AIMD) simulations have investigated and quantified the dynamic behaviour of the catalytic systems, highlighting an important increase in fluxionality in some cases which helps to explain the increase in catalytic activity

El limoneno: uno de los terpenos más usados y su papel en la industria de los bioplásticos

La mayoría de los materiales poliméricos usados diariamente se obtienen a partir de fuentes fósiles. Debido a los recursos limitados de petróleo y a los problemas generados por la contaminación de los plásticos, es necesario encontrar nuevas fuentes renovables para la obtención de materiales de uso cotidiano. Los bioplásticos obtenidos a partir de la biomasa constituyen la principal alternativa a los materiales poliméricos tradicionales obtenidos del petróleo. Dentro de la biomasa, el limoneno se revela como una plataforma química prometedora. Así pues, durante la última década el uso de limoneno se ha investigado con intensidad y actualmente se han evidenciado nuevos procesos catalíticos capaces de proporcionar excelentes productos químicos y polímeros a partir de él. En este artículo se analizarán las diferentes aplicaciones del limoneno en la industria de polímeros como precursor orgánico para la síntesis o el procesado de bioplásticos avanzados y multifuncionales

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed