Preparation and spectral study of mixed-ligand nickel(II) chelates containing N- or N,N′-methylated ethylenediamines and tropolonate or hinokitiolate ligands

Eleven mixed-ligand chelates of Ni(II) containing a molecule of N,N-di-, N,N,N'-tri-, or N,N,N',N'-tetramethylethylenediamine, and a tropolonate (trop) or hinokitiolate (hino) ligand, were prepared, and their electronic spectra in solid state and in various organic solvents were studied. Most systems studied were green, containing octahedral chelate species [Ni(trop/hino) (diamine) (H2O/Solvent)(2)](+) or [Ni(NO3) (trop/hino)-(diamine)], but some were red, containing square planar [Ni(trop/hino) (diamine)](+), and an equilibrium between the octahedral and square planar species was sometimes observed in solutions. Strong spectral resemblances with the corresponding diamine-beta-diketonate chelates of Ni(II) could be pointed out. (C) 1998 Elsevier Science Ltd. All rights reserved.