Highly Active Salen‐Based Aluminum Catalyst for the Coupling of Carbon Dioxide with Epoxides at Ambient Temperature

Abstract

Aluminum complex [(naph)salen]AlMe [(naph)salen = N,N′‐(2,3‐naphthalene)bis(3,5‐dimethylsalicylideneiminato)] was synthesized and fully characterized by NMR spectroscopy, high‐resolution mass spectrometry, elemental analysis, and single‐crystal XRD. The complex exhibits square‐pyramidal geometry around the aluminum center in the solid‐state structure, and it has a trigonality parameter τ of 0.13. Comparison of the catalytic activity of [(naph)salen]AlMe with that of four related aluminum complexes containing tetradentate salen ligands with different bridging groups revealed that the naphthyl‐bridged salen‐based aluminum complex, in conjunction with nBu4NI as cocatalyst, showed higher catalytic activity than the other complexes for the coupling of CO2 with epoxides under the mild conditions of room temperature and 5 bar of CO2 in 12 h. In addition, [(naph)salen]AlMe showed favorable features, such as requiring low catalyst loading (0.5 mol‐%) and broad epoxide substrate scope, including six terminal epoxides and three internal epoxides.

Efficient Aluminum Catalysts for the Chemical Conversion of CO2 into Cyclic Carbonates at Room Temperature and Atmospheric CO2 Pressure

“…The AlÀO, AlÀN, and AlÀCb ond lengths are all similart ot hose found in related pentacoordinate aluminum complexes. [11] The distortion of the coordination aroundt he 5- Scheme1.Synthetic routes for aluminumc omplexes. Each aluminumc omplex (X R )i sa bbreviated by using substituents Xa nd R. ChemSusChem 2019, 12,4211-4220 www.chemsuschem.org coordinate Al metal centerc an be determinedb yt he trigonality parameter, t. [12] Since the largest bond angle (a)a nd the second largesta ngle (b)a round the Al centera re ffN1-Al-O1' [155.67(29)8]a nd ffO1-AlÀC2 [120.51(13)8], respectively,t he trigonality parameter (t = [aÀb]/60) for Thio H was calculated to be 0.59.…”

“…As expect- ( Ta ble 4, entries 10 and 11). In addition, other epoxides containing halogens and aromatic halogenss howed excellent reactivities ( Table 4, entries [10][11][12][13][14]. We also investigated the synthesis of more challenging cyclic carbonatesu sing internal epoxides such as cis-cyclopentene oxide (1o), cis-3,4-epoxytetrahydrofuran( 1p), cis-cyclohexene oxide (1q), cis-cyclooctene oxide (1r), trans-2,3-butylene oxide (1s), and trans-stilbene oxide(1t)t oe lucidate the mechanism of this reaction (Figure 4).…”

Effect of bridging units on the photophysical properties of 4‐NEt2‐appended salen−indium complexes

“…This flexibility allows the salen-type ligands to have intriguing properties and broad applicability in coordinating with various metal ions. Accordingly, numerous salen-based organometallic complexes have been reported in many fields, [1][2][3][4][5][6][7][8][9] particularly attracting significant interest in optoelectronic materials. [10][11][12][13][14][15][16][17][18] Furthermore, efforts are still underway to find new types of salen-based complexes with remarkable photophysical properties.…”

Synthesis of Bio-Derived Cyclic Carbonates from Renewable Resources

“…The development of Earth-crust-abundant metal catalysts is highly desirable, and as aluminum is one of the most abundant metals on Earth and inexpensive, it could be a potential metal for the development of catalysts for large-scale biobased cyclic carbonate synthesis. Many highly efficient and selective aluminum catalysts have been previously reported. − Our research group has already developed neutral and bifunctional aluminum catalysts for cyclic carbonate synthesis under mild reaction conditions. ,,,, Some of the catalysts developed were shown to be active at room temperature and 0.1 MPa carbon dioxide pressure, catalyzing the coupling reaction of epoxides and CO 2 into cyclic carbonates in high yields. , …”