Enantiomer-differentiating Cathodic Reduction of Racemic Tris (acetylacetonato) cobalt(III) Complex with Optically Active Ammonium Electrolytes

Abstract

Kinetic resolution of tris (acetylacetonato) cobalt(III) [Co(acac)₃] by cathodic reduction was studied with optically active ammonium electrolytes. The reaction obeyed the pseudo-firstorder rate law. Enantioselectivity was elevated at low applied potential of working electrode and maximized at -1.30 V (vs. Ag/AgCl). It was also dependent on the concentration of the chiral electrolyte. Maximum enantiomer rate ratio (kΔ/kΛ) 1.10 was obtained by using (-)-N, N'-tetramethylenebis (dimethylmenthylammonium) diperchlorate. The efficiency of a pulse electrolysis which involved reduction of [Co(acac)₃] and oxidation of [Co(acac)₂] was also examined with the chiral ammonium electrolytes.