Pyrazoles and imidazoles as ligands. XV. preparation, spectra and magnetic properties of di-μ-hydroxo-bis- [di(2-methylimidazole)copper(II)] diperchlorate dihydrate

The preparation of the title compound is reported from Cu(ClO4)2, 2-methylimidazole and a small amount of water in ethanol solution. The compound consists of dimeric units [(2MIz)2Cu(OH)]22+, to which two perchlorate anions and two molecules of water are weakly coordinated. Two hydroxy groups are bridged between the two copper ions. The compound was identified and characterized with the aid of chemical analyses, infrared spectra, ligand-field spectra, magnetic susceptibility, paramagnetic resonance spectra and conductivity measurements. The magnetic measurements indicate antiferromagnetic character for the compound, with the spin singlet lying 175±1 cm−1 below the spin triplet. A Neèl point was found at 159±3°K. Paramagnetic resonance spectra at X- and O-band frequencies yielded gx = 2.06±0.01, gy = 2.05±0.01 and gz = 2.26±0.01; the axial zero-field splitting was found to be 0.72±0.01 cm−1 with an additional rhombic splitting of 0.025±0.005 cm−1. The value for the axial splitting parameter is the largest thus far observed for binuclear CuII compounds.