An Investigation of the Symmetric and Asymmetric Cleavage Products in the System Aluminum Trihalide/1-Butylimidazole

作者：Hog Michael; Schneider Marius; Studer Gauthier; Baeuerle Monika; Foehrenbacher Steffen A; Scherer Harald; Krossing Ingo^*

来源：Chemistry - A European Journal, 2017, 23(46): 11054-11066.

DOI：10.1002/chem.201701553

• aluminum
• cleavage reactions
• Lewis acids
• liquid coordination complexes
• N ligands

Mixtures of AlX3 (X=Cl, Br) with 1-butylimidazole (BuIm) in various ratios were investigated. The mixtures were characterized by multinuclear (H-1, Al-27, C-13, and N-15) NMR, IR, and Raman spectroscopy and in part by single-crystal X-ray diffraction. Depending on the molar fraction x(AlBr3) of the AlBr3-based mixtures, the cationic aluminum complexes [Al(BuIm)(6)](3+) and [AlBr2(BuIm)(4)](+), the neutral adduct [AlBr3(BuIm)], as well as the anions Br-, [AlBr4](-), and [Al2Br7](-) could be identified as the products of the symmetric and asymmetric cleavage of dimeric Al2Br6. Furthermore, there are hints at the formation of [AlBr2(BuIm)(2)](+) or related cations. Comparison of the AlBr3/BuIm system with AlCl3-based mixtures revealed the influence of the halide: In contrast to AlBr3, the trication [Al(BuIm)(6)](3+) could not be detected as main product in a 1:6 mixture of AlCl3 and BuIm. Additionally, [AlCl3(BuIm)] crystallizes from a mixture with x(AlCl3)=0.60 at room temperature, whereas the corresponding AlBr3-based mixture remains liquid even at +6 degrees C. Three AlBr3-based mixtures are liquid at room temperature, whereas all other mixtures are solids with melting points between 46 and 184 degrees C. The three liquid mixtures exhibit medium to high viscosities (117 to >1440mPas), low conductivities (0.03-0.20mScm(-1)), but high densities (1.80-2.21gcm(-3)). Aluminum could be successfully deposited from one of the neat Lewis acidic mixtures of the AlBr3-based system.

• 出版日期2017-8-16