The irreversible reaction of chlorocobalt(III) tetramethylchiroporphyrin CoCl(TMCP), 1, with nitrogen donor ligands L, such as primary amines and aziridines, in deuterated chloroform solution at room temperature gives cationic bis-adducts of the type [Co(L)2(TMCP)]+Cl− in quantitative yields. Upon binding to the chiral host 1, the protons of L experience a shielding by the porphyrin, and several of their 1H NMR signals are shifted to a vacant spectral window upfield of tetramethylsilane (0 > δ > −6.5). The coordinated (R) and (S) enantiomers show well-resolved signatures at 200 MHz, allowing their relative concentrations to be readily determined by peak integration. Racemic amine derivatives such as 2-butylamine, 1-aminoindane, α-amino-γ-butyrolactone, 1-phenylethylamine, 2-aminomethoxypropane and 1-(1-naphthyl)ethylamine bind to 1 in CDCl3 solution without detectable kinetic resolution, affording a 1:1 concentration ratio of the two cobalt-bound enantiomers (RCo) and (SCo), as measured by 1H NMR. Aziridines such as ethyl 2-aziridinecarboxylate and 2-aziridinemethanol behave in an analogous manner. Standard solutions of 1-(1-naphthyl)ethylamine covering a range of enantiomer compositions x = (R)/[(R) + (S)] (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, 1) were analyzed using 1 as a chiral NMR shift reagent. The bound enantiomer composition values y = (RCo)/[(RCo) + (SCo)] measured by NMR were in good agreement with those of the standard solutions, and the calibration curve y = f(x) was linear in the range 0⩽x⩽1, within experimental error. These features of 1 as a chiral analytical reagent may prove suitable for the accurate determination of a wide range of enantiomeric excesses of amines and aziridines. The crystal structures of {Co[(R)-1-(1-naphthyl)ethylamine]2(TMCP)}+Cl− and {Co[(R)-2-butylamine]2(TMCP)}+Cl− are described.
