Application of Polysaccharide-Based Chiral HPLC Columns for Separation of Nonenantiomeric Isomeric Mixtures of Organometallic Compounds

Abstract

A series of polysaccharide-based chiral stationary phase (CSP) columns, Daicel Chiralpak IA, IB, and IC, were applied in the separation of the nonenantiomeric isomers of various organometallic compounds and were found to be highly effective in recognizing isomers of minor structural differences. The CSP columns have succeeded to separate the double-bond regioisomers in bridged (η5-formylcyclopentadienyl)manganese(I) dicarbonyl complexes 1a/1b, the structural isomers of methylbutenylferrocene derivatives in 2a/2b and 3a/3b, and the geometrical isomers of the (2-methyl-2-butenyl)ferrocenes in (Z)/(E)-3b. Due to the close similarity of the isomeric compounds in these mixtures, separations of the components are extremely difficult and could not be attained by conventional methods such as silica gel column chromatography, silica gel HPLC, recrystallization, distillation/sublimation, etc. Clearly, the polysaccharide-based CSP columns have unique advantages in separation/purification technology, and this study has shown potential usefulness of the CSP columns in separation of not only enantiomeric but also nonenantiomeric mixtures.