Ligand fields factors affecting

It is well-established that the molecular and electronic structures of metal complexes of azamacrocycles are greatly affected upon N-alkylation (197). This is mainly due to two factors (a) the decrease of the ligand field strength and (b) the increase in the steric requirements upon going from a secondary to a tertiary amine donor function (251). To examine whether the properties of the dinuclear amine-thiophenolate complexes are affected by the N-alkyl substituents, analogous complexes of the... 

Alfred Werner studied the "strengthening of the primary valence force by the saturation of the secondary valence force," but he failed to explain fully this phenomenon. To elucidate the stabilization of unstable oxidation states by complex formation two aspects should be taken into account the thermodynamic stability of complexes and their kinetic redox lability. Such factors as ligand field stabilization energy for M" and and the geometry of the donor atoms spatial orientation also affects the stability of a given oxidation state. Macrocyclic ligands are especially suitable for the stabilization of unstable metal oxidation states, both from the thermodynamic and kinetic viewpoints. 

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