Stereoisomers of the Bis(l-hydrogenaspartato)trimethylenediaminecobalt(III) Complex

Abstract

Abstract The bis(l-hydrogenaspartato)trimethylenediaminecobalt(III) complex has been prepared by the reaction of the trans-[CoCl2(tn)2]+ complex with l-aspartic acid, and its eight stereoisomers have been separated by an ion-exchange chromatographic method. The six isomers are trans(O)-Λ and -Δ, cis(O)cis(N)-Λ and -Δ and trans(N)-Λ and -Δ isomers, in which either aspartate ion forms the five-membered chelate ring through an N atom of the amino group and an O atom of the α-carboxylate group. The remaining isomers are Λ- and Δ-trans(O) ones containing a five-membered chelate ring and a six-membered ring of l-aspartate ions. On the other hand, stereoselective formations have been found in the Λ,Δ, and Λ isomers for the trans(O), cis(O)cis(N), and trans(N) isomers respectively. It has become apparent that these stereoselectivities agree with those found for the corresponding l-pn and en complexes, while the orders of the formation amounts for the three geometrical isomers disagree.