Pentacoordinated Ni(bidentate)(tridentate) chelates and their hydrates

Abstract

Reaction of bis(acetylacetonato)nickel(II), Ni(acac)₂ (dihydrate or anhydrous), with tridentate Schiff bases (HB) in boiling toluene followed by exposure of the reaction mixture to moist air leads to the ready isolation of crystalline complexes of composition Ni(acac)(B) (OH₂). Their spectral and magnetic properties are in accord with pseudooctahedral geometry. On heating, these complexes readily dehydrate giving rise to Ni(acac) (B). These have infrared spectra characteristic of the mixed ligand formulation. Their electronic spectra can be readily fitted with high-spin square pyramidal geometry. In moist solvents the equilibrium between Ni(acac) (B) and Ni(acac)(B)(OH₂) can be identified from spectral data. The thermodynamics for this equilibrium has been studied in one case using variable temperature spectral results.