Structural non-regidity of tricyclic Cd(2) and Zn(2) complexes

Using the method of dynamic NMR 1H a series of tricyclic Cd(2) and Zn(2) complexes of the type 1 on the basis of tetradentate ligands, for which variation of the number (n) of methylene groups of diamine fragment permits to realize both a plane (n=2) and a pseudotetrahedral (n=4, 6) configurations of the central metal atom, is synthesized and studied. It is established that processes of structural non-rigidity in solutions of tricyclic Cd(2) and Zn(2) complexes of the type (1) include degenerated intermolecular reactions of ligand exchange, and for compounds with the pseudotetrahedral configuration of the central atom -intermolecular inversion Δ ↔ Λ as well. The free activation energy of degenerated ligand exchange of 111Cd(2) compounds of the type (1) depends on the number of diamine fragment links and lies within the limits 63-80 kJ/mol. The activation free energy of interconversion Δ ↔ Λ for Cd(2) compounds is ∼ 63 kJ/mol