FACTORS DETERMINING THE LIGAND-FIELD STABILIZATION ENERGIES OF THE HEXAAQUA-2+ COMPLEXES OF THE FIRST TRANSITION SERIES AND THE IRVING-WILLIAMS ORDER

A new analysis of the ligand field stabilization energy, which makes allowance for the nephelauxetic effect, is shown to give satisfactory results for the hexaaqua 2+ complexes of the first transition series. Previous treatments only considered d-orbital splitting energies, and they seem successful because irregularities in the changes in interelectronic repulsion energy during complex formation are counterbalanced by those in spin-orbital coupling energies, and in the relaxation energies associated with the contraction in internuclear distance brought about by the effects of the ligand field. The weak nephelauxetic effect of water as a ligand contributes to the emergence of the Irving-Williams order of stability in complexing reactions of Mn2+ --> Zn2+ ions in aqueous solution. This is established with thermodynamic and spectroscopic data on ethylenediamine complexes.