Synthesis and characterization of ionic liquids based upon 1-butyl-2,3-dimethylimidazoliumchloride/ZnCl2

Trialkylimidazolium chlorozincate molten salts resulting from the combination of zinc chloride and 1-butyl-2,3-dimethylimidazolium chloride, [BMMI][Cl], have been prepared with a mole percent of ZnCl2, R (R = n(ZnCl2)/n(ZnCl2) + n([BMMI][Cl])) equal to 0, 0.1, 0.25, 0.33, 0.5, 0.66, 0.75. Their analyses by DSC, C-13, H-1 and Cl-35 solid state and solution NMR, and mass spectrometry (ESI, MS/MS) are consistent with the presence of [BMMI][Cl] and [BMMI][ZnCl3] for R < 0.5; pure [BMMI][ZnCl3] for R = 0.5, and [BMMI][ZnCl3] with [BMMI][Zn3Cl7] for R > 0.5. Infrared spectra realized in the presence of pyridine show that the Lewis acidity of ZnCl2-[BMMI][Cl] increases with R. High temperature (110 degrees C) C-13 and Cl-35 NMR experiments on neat [BMMI][ZnCl3] (R = 0.5) evidenced that its structure varies with time from [BMMI][ZnCl3] to [BMMI...Cl...ZnCl2].