1980 Volume 53 Issue 8 Pages 2257-2261
((2S,S′-1,1′-Trimethylenedipyrrolidine-2,2′-dicarboxylato)(α-amino carboxylato)cobalt(III) complexes were prepared and characterized, where the α-amino carboxylate ligand is glycinate, (R)- or (S)-alaninate, (R)- or (S)-valinate, sarcosinate, N-ethylglycinate, (R)-prolinate, or (S)-pipecolate ((S)-2-piperidinecarboxylate). Of the three possible isomers, only the Λ-uns-mer form was prepared for each of the complexes except for the glycinato complex. The (R)-prolinato and (S)-pipecolato complexes were stereoselectively prepared by using (RS)-proline or (RS)-pipecolic acid. The pipecolate ion coordinated selectively was assigned to S(C) configuration on the basis of the CD measurement of the 2,4-dinitrophenyl-pipecolic acid. The nitrogen atom of the sarcosinate, N-ethylglycinate, (R)-prolinate, or (S)-pipecolate ion, which coordinated stereoselectively to Co(III) ion, took the R(N) configuration. The stereoselectivity in this work was discussed on the basis of the electronic absorption, CD, and PMR spectra.
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