Conformational inversion of 2, 2'-bipyridine 1, 1'-dioxide chelate ring in a series of (2, 2', 2'-triaminotriethylamine) (4, 4'-disubstituted-2, 2'-bipyridine 1, 1'-dioxide)cobalt(III) complexes

摘要

A new series of cobalt(III) complexes, [Co(2, 2', 2"-triaminotriethylamine) (4, 4'-X_2bpdo)]~3+ (X=Me, MeO, EtO), where 4, 4'-X_2bpdo denotes 4, 4'-disubstituted-2, 2'-bipyridine 1, 1'-dioxide, were prepared. The complexes were resolved into a pair of enantiomers (conformational optical isomers), and gradually racemized in water by conformational inversion of the skewed 4, 4'-X_2bpdo chelate ring, #delat#<=>#lambda#. The rate of racemization is remarkably reduced with an inerease in the electron-releasing ability of the 4, 4'-X_2 substiuents on bpdo.