Studies of Titanium(IV) Chloride in a Strongly Lewis Acidic Molten Salt:Electrochemistry and Titanium NMR and Electronic Spectroscopy

摘要

The electrochemistry of titanium(IV) has been examined in acidic (AlCl3-rich)compositions of the ambient-temperature molten salt, AlCl3-1-ethyl-3-methylimidazolium chloride (ImCl). Titanium is reduced to Ti(III) and Ti(II) in two one-electron steps, both of which exhibit slow electron-transfer kinetics. The (49)Ti NMR spectra for TiCl4 and TiCl3-rich melts exhibits a resonance at -4 ppm (49)Ti = 0 ppm for neat TiCl4. In basic (chloride-rich) melts, the (49)Ti resonance for TiCl6 is found at -237 ppm. In acidic metls, Ti(IV) is alkylated upon addition of MeAl2Cl3 and is slowly reduced to Ti(III). Combination of TiCl4 and Me3Al2Cl3 in an acidic melt is demonstrated to be catalytic system for ethylene polymerization.