Theoretical Study on the Disproportionation Reaction of Nickel(II) Mixed Ligand Complexes

Abstract

Nickel(II) mixed ligand complexes are of interest due to their thermochromic and solvatochromic properties, which will lead to their use as thermosensitive coloring matter, various sensors and indicators, particularly as a Lewis-acid-base indicator. Density functional theory, B3LYP/CEP-31G calculations, were performed on nickel(II) complexes comprising N,N,N',N'-tetramethylethylenediamine (tmen), benzoylacetonate (bzac) and a halide anion (X), Ni(tmen)(bzac)X n(H2O)(n = 1-4, X = Cl, Br, I). Fully optimized geometries of [Ni(bzac)2(tmen)], [NiCl(bzac)(tmen)(H2O)] and [Ni(bzac)(tmen)(H2O)2]+ are all in good agreement with crystallographic data. This series of nickel(II) complexes shows a disproportionation reaction in a non-polar and rather inert solvent, such as 1,2-dichloroethane and acetone, accompanied by highly contrasting color changes of the solutions. Also the presence of an intermediate compound has been confirmed. A possible reaction mechanism of this reaction as well as the structure of the intermediate compound is discussed.