Highly Efficient NMR Enantiodiscrimination of Chiral Octanuclear Metalla-Boxes in Polar Solvent

Self-assembly of 5,10,15,20-tetra(4-pyridyl)porphyrin (tpp-H-2) and 5,10,15,20-tetra(4-pyridyl)porphyrin-Zn(II) (tpp-Zn) tetradentate panels with the dinuclear p-cymene ruthenium clips [Ru-2(eta(6)-p-(PrC6H4Me)-C-i)(2)(mu-C2O4-kappa O)Cl-2] and [Ru-2(eta(6)-p-PriC(6)H(4)Me)(2)(mu-C2O4-kappa O)Cl-2] C2O4 = oxalato: C6H2O4 = 2,5dihydroxy-1,4-benzoquinonato) affords the cationic organometallic boxes [Ru-8(eta(6)-p-(PrC6H4Me)-C-i)(8)(mu(4)-tpp-H-2-kappa N)(2)(mu-C2O4-kappa O)(4)](8+) ([1](8+)), [Ru-8(eta(6)-p-(PrC6H4Me)-C-i)(8)(mu(4)-tpp-H-2-kappa N)(2)(mu-C6H2O4-kappa O-4](8+) ([2](8+)), [Ru-8(eta(6)-p-(PrC6H4Me)-C-i)(8)(mu(4)-tpp-Zn-kappa N)(2)(mu-C2O4-kappa O)(4)](8+) ([3](8+)), and [Ru-8(eta(6)-p-(PrC6H4Me)-C-i)(8)(mu(4)-tpp-Zn-kappa N)(2)(mu(4)-C6H2O4-kappa O)(4)](8+) In solution, for all these complexes, a rapid and effective enantiodifferentiation was achieved in the presence of the NMR chiral solvating agent A-BINPHAT anion, only 0.05 to 0.10 equiv being necessary for complete baseline-to-baseline separation of some of the proton signals of the enantiomers. To add to this highly effective discrimination, on experiments were performed in the high-polarity solvent CD3CN, a solvent traditionally not favorable for effective chiral ion-pairing phenomena.