Pyrazoles and imidazoles as ligands. II. Coordination compounds of N-methyl imidazole with metal perchlorates and tetrafluoroborates

Abstract

A number of new coordination compounds containing N-methyl imidazole (NMIz) as a ligand is reported. The compounds have the general formula M(NMIz) m(anion) n, in which MAg I or one of the divalent metal ions Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd; m = 2,4 or 6, the anions are ClO 4 − or BF 4 −, whereas n = 1 or 2. The compounds are prepared from the (hydrated) metal salts and the proper ligand in ethanol solution. Characterization and identification of the compounds occurred with the aid of chemical analyses, X-ray powder diagrams, ligand-field spectra, infrared and ramanspectra, magnetic susceptibility measurements and paramagnetic resonance spectra. Several compounds of the same stoichiometry were found to be mutually isomorphous. The ligand NMIz is believed to be coordinated via the pyridine nitrogen of the molecule, to all metal ions. Magnetic data, such as the magnetic moments, g-values, nuclear hyperfine splittings, zero-field splittings, all agree with the proposed stoichiometry. Ligand-field parameters are determined for the octahedral ions M(NMIz) 6 2+ with M = Fe, Co, Ni, and for the square-planar Cu(NMIz) 4 2+, and compared with M(imidazole) n 2+ ions. Far-infrared and raman spectra indicate MN stretching frequencies in the 350–150 cm −1 range, as found for many other nitrogen-donor ligands.