Collect. Czech. Chem. Commun. 1982, 47, 465-475

Conformational analysis of metal chelates. A molecular mechanical study of the relative stability of cobalt(III) 2,3-diaminobutane-N,N,N',N'-tetraacetate complexes

František Pavelčík and Jaroslav Majer

Department of Analytical Chemistry, Pharmaceutical Faculty, Comenius University, 832 32 Bratislava


The stereochemistry and relative energy of diastereoisomers of Λ-[Co(DBTA)]- were studied in dependence on the absolute configuration of the ligand using molecular mechanical calculations. The calculated thermodynamic stabilities of the complexes decrease in the order (S, S)-DBTA (R,S)-DBTA (R,R)-DBTA. The destabilization factors are primarily repulsion non-bonding interactions between the axial methyl group and atoms of the acetate ring, R. (S,S)- and (R,R)-DBTA exhibit high diastereoselectivity in octahedral complexes. The large steric strain in the meso-DBTA complex can lead to opening of one chelate ring.