Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Four Isomers of the Bis(ethylenediamine)sarcosinatocobalt(III) Ion: Separation, Identification, and Characterization
Miho FujitaYuzo YoshikawaHideo Yamatera
Author information

1977 Volume 50 Issue 12 Pages 3209-3215


All four possible isomers of the bis(ethylenediamine)sarcosinatocobalt(III) ion, [Co(sar) (en)2]2+, were separated chromatographically on the column of an SP-Sephadex cation exchanger, and their absorption, circular dichroism, and 13C NMR spectra were measured. The more stable pair of isomers were identified as Δ-[Co(S-sar) (en)2]2+ and Λ-[Co(R-sar) (en)2]2+, while the less stable pair were Δ-[Co(R-sar) (en)2]2+ and Λ-[Co(S-sar) (en)2]2+. The Δ-[Co(S-sar) (en)2]2+ isomer in an aqueous solution showed mutarotation which can be ascribed to a change in configuration (epimerization) about the sarcosinato nitrogen atom. In equiribrium at 25°C, the mixture consisted of 84.8% of the Δ(S) isomer and 15.2% of the Δ(R) isomer. From this result, the free-energy difference between the isomers was estimated to be 4.26 kJ mol−1. The presence of the less stable isomers, which were not found by Buckingham et al., was also confirmed by the 13C NMR measurements.

Information related to the author

This article cannot obtain the latest cited-by information.

© The Chemical Society of Japan
Previous article Next article