
TY  - JOUR
A1  - Bernhardt, Paul V. 
A1  - Dyahningtyas, Tri Erny 
A1  - Harrowfield, Jack M. 
A1  - Kim, Jee-Young 
A1  - Kim, Yang 
A1  - Rukmini, Elisabeth 
T1  - Chiral Resolution of Hexaamine Cobalt(<emph type="6">III</emph>) Cages: Substituent Effects on Chiral Discrimination
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 2003
VL  - 56
IS  - 12
SP  - 1187
EP  - 1191
KW  - 
UR  - https://doi.org/10.1071/CH03160 
N2  - Chiral resolution of the cobalt cage complexes [Co(diNOsar)]3+ and [Co(diAMsarH2)]5+ have been achieved by selective crystallization with the anion bis-&#956;-(R), (R)-tartratodiantimonate(III) ([Sb2(R,R-tart)2]2&#8211;) and also by column chromatography with Na2[Sb2(R,R-tart)2] as eluent. The X-ray crystal structures of &#x039B;-[Co(diNOsar)][Sb2(R,R-tart)2]Cl . 7 H2O and &#916;-[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 (&#x039B;-enantiomer) to ammonio &#916;-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&#8211; anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na2[Sb2(R,R-tart)2] as eluent, &#x039B;-[Co(diNOsar)]3+ elutes first, which implies a tighter ion pairing interaction than for the &#916;-enantiomer. On the other hand, &#916;-[Co(diAMsarH2)]5+ elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between &#916;-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2&#8211; relative to &#x039B;-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2&#8211;. 
ER  -

