Bifunctional Aluminum Catalysts for the Chemical Fixation of Carbon Dioxide into Cyclic Carbonates

Abstract

Bifunctional aluminum complexes supported by novel zwitterionic NNO-donor scorpionate ligands were found to be efficient bifunctional catalysts for cyclic carbonate synthesis from terminal and internal epoxides in good yields and with broad substrate scope. Neutral scorpionate ligands (1–2) were designed and used as precursors to obtain two novel zwitterionic NNO-heteroscorpionate ligands (3–4). Reaction of 3 or 4 with [AlX3] (X = Me, Et) in a 1:1 or 1:2 molar ratio afforded the mononuclear and dinuclear cationic aluminum complexes [AlX2{κ2-mbpzbdmape}]­I2 (X = Me (5), Et (6)), [AlX2{κ2-mbpzbdeape}]­I2 (X = Me (7), Et (8)), [{AlX2(κ2-mbpzbdmape)}­(μ-O)­{AlX3}]­I2 (X = Me (9), Et (10)), and [{AlX2(κ2-mbpzbdeape)}­(μ-O)­{AlX3}]­I2 (X = Me (11), Et (12)) with elimination of the corresponding alkane. These complexes were investigated as catalysts for cyclic carbonate formation from epoxides and carbon dioxide in the absence of a co-catalyst. Complex 7 was found to be the most active catalyst for cyclic carbonate formation from various epoxides and carbon dioxide.

Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts

“…Deuterated solvents were stored over activated 4 Å molecular sieves and degassed by several freeze-thaw cycles. The synthesis of ligand precursors and zinc complexes was carried out as previously reported [53][54][55]. Cyclohexene oxide (Sigma-Aldrich, Munich, Germany) was pre-dried over calcium hydride, distilled under vacuum and stored under nitrogen in a glove box.…”

Cycloaddition of atmospheric CO2to epoxides under solvent-free conditions: a straightforward route to carbonates by green chemistry metrics

“…In the closely related investigation, the same research team showed that performing the process in the presence of 5 mol% of aluminum-based complex 31 as a catalyst and without any cocatalyst at 35 C afforded the expected carbonates 33 in high to excellent yields (Scheme 19). 55…”

Efficient Synthesis of Cyclic Carbonates from Unsaturated Acids and Carbon Dioxide and their Application in the Synthesis of Biobased Polyurethanes

“…Additionally, we have previously reported the use of heteroscorpionate metal complexes as efficient catalysts for cyclic carbonate formation [11i,18] . For instance, single‐component aluminum catalysts have shown to be efficient catalysts for the preparation of various cyclic carbonates using a low catalyst loading (0.25–2.50 mol %) under relatively mild reaction conditions (70–90 °C and 10 bar pressure) [18b,c] . Recently, we have focused our interest towards the employment of waste‐derived starting materials for the preparation of bio‐based cyclic carbonates derived from terpenes and furan derivatives [11i] .…”