Direct High-performance Liquid-chromatographic Resolution of Planar Chiral Tricarbonyl (eta(6)-arene)-chromium(0) Complexes

Thirty-four disubstituted tricarbonyl (eta(6)-arene)-chromium complexes having planar chirality were examined by HPLC on a recently developed chiral stationary phase (CSP). This CSP contains ''active sites'' comprised of clefts formed by the perpendicular disposition of pi-acidic 3,5-dinitrobenzamide groups relative to pi-basic naphthyl groups. Thirty of the thirty-four show different retention factors for their enantiomers. A mechanistic hypothesis which accounts for the enantiodiscrimination is presented. The arene, using the face anti to the tricarbonylchromium, enters the cleft and undergoes simultaneous face-to-face and face-to-edge pi-pi interactions with the aromatic ''walls'' of the cleft. Hydrogen bond formation provides a third attractive interaction, facilitating enantiodiscrimination.