NICKEL(II) COMPLEXES OF IMIDAZOLEDERIVED LIGANDS WITH AN AMIDE GROUP: SOME COMPOUNDS WITH COMPLEX MAGNETIC BEHAVIOUR

摘要

NiL_4X_2 centre dot H_2O compounds [L = 1-(2-carbamoylethyl)-4-methylimidazole (C4MIm), 1-(2-carbamoylethyl)benzimidazole (CBIm) or 1-(2-carbamoylethyl)-5, 6-dimethylbenzimidazole (CMMBIm)] have been prepared and characterized and the effect of different axial ligands, X, on the magnetic properties of the complexes has been examined. Diamagnetic and paramagnetic complexes with CMMBIm habe been obtained With C4Mim and CBIm, only paramagnetic compounds could be isolated. The CBIm ligand afforded complexes with unusual magnetic behaviour: NiCl_2(CBIm)_4 is believed to exhibit a spin-singlet ground state with a low-lying spin triplet state and NiBr_2(CBIm)_4 shows magnetic properties indicating structural changes over the temperature range studied. Structures of the compounds have been proposed based on spectroscopic and magnetic data and on powder X-ray diffraction patterns.