Electrochemical Investigation of Ketone Complexation by Lewis Acids in a Chloroaluminate Ionic Liquid

Abstract

A comparative study of 9-fluorenone electrochemistry in the AlCl3 : 1-ethyl-3-methylimidazolium chloride system has been carried out by addition of the Lewis acids AlCl3 and HfCl4 to fluorenone initially in the neutral melt. It has been found that each Lewis acid is capable of forming a complex with fluorenone, resulting in a positive peak potential shift for the reduction process. Neither these peak potentials, nor the colors of the complexes, are exactly the same, indicating that distinct complexes are formed for HfCl4 and AlCl3. There is some possibility of interaction of HfCl4 with the chloroaluminate melt to form the Lewis acid Al2Cl7-, but this route seems to play a minor role in the present case.