Structure of bis[ethyl (trifluoroacetyl)acetato]copper(II) and its adduct with 4-(dimethylamino)pyridine: EPR and X-ray study

Bis[ethyl (trifluoroacetyl)acetato]copper(II), [Cu(etfac)2], has been prepared and studied by X-ray crystallography and EPR spectroscopy. The complex is centrosymmetrical and crystallizes in the P21/c space group with two formula units per unit cell. After dissolving of the complex in solid matrix or in suitable solvents some changes are detected in the EPR spectra and are discussed. The EPR spectra of the complex magnetically diluted in the corresponding Pd(II) complex reveal the presence of only one paramagnetic species further denoted as B. However, EPR spectra measured in solution indicate the presence of two different paramagnetic species: (i) non-distorted parent species B, and (ii) rhombic-distorted species A, which prevail in solutions. The A:B species ratio is a function of the solvent and temperature. The [Cu(etfac)2] adduct with 4-(dimethylamino)pyridine has also been studied and found to crystallize in the C2/c space group. The adduct EPR spectrum monitored in solution shows the presence of only one paramagnetic species. q 2003 Elsevier B.V. All rights reserved