Chiral resolution of the cobalt cage complexes [Co(diNOsar)]3+ and [Co(diAMsarH2)]5+ have been achieved by selective crystallization with the anion bis-μ-(R), (R)-tartratodiantimonate(III) ([Sb2(R,R-tart)2]2–) and also by column chromatography with Na2[Sb2(R,R-tart)2] as eluent. The X-ray crystal structures of Λ-[Co(diNOsar)][Sb2(R,R-tart)2]Cl . 7 H2O and Δ-[Co(diAMsarH2)][Sb2(R,R-tart)2]2Cl . 14 H2O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Λ-enantiomer) to ammonio Δ-enantiomer) and shows that the ammonio-substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb2(R,R-tart)2]2– anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na2[Sb2(R,R-tart)2] as eluent, Λ-[Co(diNOsar)]3+ elutes first, which implies a tighter ion pairing interaction than for the Δ-enantiomer. On the other hand, Δ-[Co(diAMsarH2)]5+ elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Δ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2– relative to Λ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2–.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.