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

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