Isomeric macrocyclic tetramine complexes of cobalt(III). Some problems of stereochemistry and chemical reactivity

Abstract Cis-trans and ligand configurational equilibria have been investigated in several Co III (N 4 )X 2 complexes, where (N 4 ) designates a Curtis-type macrocyclic tetraamine ligand. Ligand configurational isomers are assumed to result from changes in the configuration of atoms around asymmetric coordinated nitrogen atoms. Several new isomers have been detected and tentatively assigned structures. Interconversion between isomers has been found to be relatively rapid in dilute acid. Several ligand configurations of trans -Co(N 4 )(OH 2 ) 2 3+ appear to have about the same energy as the most stable cis -diaquo isomer, whereas cis -Co(N 4 )Cl 2 + has been shown to be far less stable than trans -Co(N 4 )Cl 2 + .