Enantiomeric Separations of Ruthenium(II) Polypyridyl Complexes Using High-Performance Liquid Chromatography (HPLC) with Cyclodextrin Chiral Stationary Phases (CSPs)

Rapid, highly efficient, analytical resolution of the enantiomers of eight different monomeric ruthenium(II) polypyridyl complexes has been achieved using HPLC with cyclodextrin chiral stationary phases. This technique also proved capable of separating both of the diastereomers and the enantiomers of one dinuclear complex in a single run, whereas similar efforts with another dinuclear complex gave only one stereoisomer cleanly. Factors such as the stereochemistry of the chiral selectors, solvent polarity, and salt effects can be altered to provide precise control of the enantioselective interactions. The ability to quickly and quantitatively determine the enantiopurity of a given ruthenium complex allowed facile reexamination and optimization of the commonly used bulk resolution procedures based on diastereomeric coprecipitation with sodium arsenyl (+)-tartrate or sodium arsenyl (−)-tartrate salts.