FIVE-COORDINATED MIXED LIGAND NICKEL(II) COMPLEXES: THERMODYNAMIC AND SPECTROSCOPIC STUDIES OF SOLVATOCHROMIC AND THERMOCHROMIC PROPERTIES

Abstract

Abstract Five-coordinate Ni(II) complexes (Ni(β-dike)(pmdt)X; β-dike− = acetylacetonate or benzoylacetonate, pmdt = N, N, N′, N″, N″-pentamethyldiethylenetriamine and X = BPh4 − or NO3 −) have been prepared and characterized by vibrational and electron spectroscopy and by magnetic measurements. BPh4 − complexes are five-coordinate species in non-coordinating solvents like DCE or NM. In solvents with stronger donor properties like DMF or DMSO, or in the case of NO3 − complexes, octahedral species are formed. Spectrophotometric titration was used to evaluate equilibrium constants between five- and six-coordinated species. Reaction enthalpies and entropies were measured. The latter was found to govern the overall fee energy changes. Steric factors appear to be important when large amine molecules are coordinated to Ni(II).