The coordination chemistry of 2-imidazolidinone

Abstract

A number of complexes having the general formula M(EU) n(anion) 2 is described, in which M 2+ = Mg, Mn, Co, Ni, Cu, Zn and Cd, Eu stands for 2-imidaziolidinone (also called, N, N′-ethyleneurea), n varies from 1 to 7, and the anions are ClO 4 −, BF 4 −,NO 3 −, NCS −, Br − and Cl −. The compounds have been analysed and characterized by chemical analyses, infrared spectra, ligand-field spectra, X-ray powder diagrams and ESR spectra. In compounds with 6 or 7 ligands per metal ion, the metal ions are found to be octahedrally coordinated by six EU ligands. A seventh ligand is sometimes held in the crystal lattice. In compounds with less than six ligands per metal ion, the geometry around the metal ion is tetrahedral or distorted octahedral, depending upon the particular combination of M and anion. The position of the CO stretching frequency in the infrared, which is unusually taken as a measure for the coordination site of amides, appears to be not indicative for the present ligand. The origin seems to be intense mixing of the amide vibrations, making that both the cation and the anion (coordinating respectively with the CO and NH groups) influence these vibrations in opposite directions. All spectral data agree with oxygen coordinated imidazolidinone ligands, this is usually observed with this type of ligands in combination with first-row transition metal ions, although bridging ligands with one CO and NH as coordinating site may also occur.