Aluminum Species and the Synthesis Mechanism of AlCl₃–CuCl–Arene Solutions

Abstract

Aluminum species in AlCl3–arene and AlCl3–CuCl–arene solutions (including benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene) were investigated using 27Al NMR and infrared (IR) spectroscopy. The AlCl3·arene and Al2Cl6·arene complexes were demonstrated experimentally. AlCl3 could not coordinate with benzene and toluene at a low temperature (40 °C) but could form complexes at a high temperature (80 °C). AlCl3 could coordinate with xylene and mesitylene to form Al2Cl6·arene complexes at both low and high temperatures (40 and 80 °C). As for AlCl3–CuCl–arene solutions with a molar ratio of 1:1:2, two signals were observed in 27Al NMR spectra. The signal at around 101 ppm was assigned to CuAlCl4·2arene complexes, and the other signal at around 96 ppm belonged to AlCl3·arene complexes. The characteristic peaks of AlCl3–CuCl–arene solutions in IR spectra moved toward the low field due to the strong π-back-bonding. The CuAlCl4·2arene complexes would convert to CuAl2Cl7·2arene complexes with a further increase in AlCl3 content when the molar ratio of AlCl3/CuCl exceeded 1. The synthesis mechanism of AlCl3–CuCl–arene solutions was analyzed by in situ Fourier transform IR (FTIR) spectroscopy. Three reaction pathways originating from different aluminum species were proposed.

Chloride and Hydride Transfer as Keys to Catalytic Upcycling of Polyethylene into Liquid Alkanes

“…This observation is consistent with the findings of Wu et al. regarding the associations in AlCl 3 –arene solutions [44] . Introducing i C 5 to the mixture affects the anhydrous AlCl 3 solubility, as evidenced by the signal at 0 ppm.…”

“…The signals observed at 0 ppm were ascribed to solid AlCl 3 powder. Upon the addition of DCM, two distinct peaks were observed at 92 ppm and 99 ppm, corresponding to Al 2 Cl 6 species and the AlCl 3 ‐DCM complex, respectively [44,45] . An excessive amount of solid AlCl 3 in DCM resulted in prominent peaks at 0 ppm and 99 ppm, suggesting that Al 2 Cl 6 coordinated with DCM to form an increased amount of the AlCl 3 ‐DCM complex (AlCl 3 ←ClCH 2 Cl), as illustrated by the equilibrium: Al 2 Cl 6 (92 ppm)+2CH 2 Cl 2 ⇌2AlCl 3 ‐CH 2 Cl 2 (99 ppm).…”

“…Upon the addition of DCM, two distinct peaks were observed at 92 ppm and 99 ppm, corresponding to Al 2 Cl 6 species and the AlCl 3 -DCM complex, respectively. [44,45] An excessive amount of solid AlCl 3 in DCM resulted in prominent peaks at 0 ppm and 99 ppm, suggesting that Al 2 Cl 6 coordinated with DCM to form an increased amount of the AlCl . This observation is consistent with the findings of Wu et al regarding the associations in AlCl 3 -arene solutions.…”

Chloride and Hydride Transfer as Keys to Catalytic Upcycling of Polyethylene into Liquid Alkanes

“…This observation is consistent with the findings Wu et al regarding the associations in AlCl 3 -arene solutions. [44] Introducing iC 5 to the mixture affects the anhydrous AlCl 3 solubility, as evidenced by the signal at 0 ppm. Notably, it also results in an increase in the resonance intensity at 99 ppm and a concurrent decrease in the Al 2 Cl 6 signal at 92 ppm.…”

“…Upon the addition of DCM, two distinct peaks were observed at 92 ppm and 99 ppm, corresponding to Al 2 Cl 6 species and the AlCl 3 -DCM complex, respectively. [44,45] An excessive amount of solid AlCl 3 in DCM resulted in prominent peaks at 0 ppm and 99 ppm, suggesting that Al 2 Cl 6 coordinated with DCM to form an increased amount of the AlCl . This observation is consistent with the findings Wu et al regarding the associations in AlCl 3 -arene solutions.…”