The Pfeiffer Effect of [Co￥±(acac)2(diamine)] with Cinchona Alkaloid in Some Organic Solvents

摘要

The Pfeiffer effect was examined on the systems of racemic [Coケ(acac)2(diamine)] with d-cinchonine and l-cinchonidine as chiral environment substances in methanol, ethanol, chloroform and methanol-chloroform mixture solvents. It was found that the ツ-enantiomer is enriched for the [Coケ (acac)2(diamine)]-d-cinchonine system, but the ニ -enantiomer is enriched for the [Coケ (acac)2(diamine)]-l-cinchonidine system. The complexes having no N-H protons such as [Coケ (acac)2(bpy)] and [Coケ(acac)2(phen)] were Pfeiffer-inactive in alcoholic solvents, where bpy = 2,2`-bipyridine and phen = 1,10-phenanthroline. This was interpreted to mean that the hydrogen bonding between N-H proton of diamine ligand and C-9 hydroxyl group of alkalid plays an important role in the chiral discrimination. And the rate of antiracemization (kanti) by the Pfeiffer effect was also measured for the [Coケ (acac)2(diamine)]-d-cinchonine system in alcoholic solvents. It was found that the rate of appearance of the Pfeiffer effect was enhanced as the concentration of added chloroform is increased.