Reinvestigation of the crystal structure and cryomagnetic behaviour of copper(II) propionates

Two different complexes of copper(II) propionates, [Cu(C2H5CO2)(4)] (1) and Na[Cu-4(C2H5CO2)(9)(H2O)(3)] (2) have been isolated from the reaction of Cu(II)(NO3)(2)3H(2)O with propionic acid in an aqueous solution of NaOH. X-ray structural analysis revealed that complex 1 consists of a one-dimensional chain of an apical-to-basal Cu-O-Cu linkage of pairwise binuclear anhydrous cupric propionates, which agrees with results previously reported. Compound 2 consists of a cation Na+ which interacts with six oxygen atoms of carboxylate groups, and anionic [Cu-4(C2H5CO2)(9)(H2O)(3)](-) ion, which contains one isolated syn-syn-carboxylato dimeric copper(II) complex [Cu-2(C2H5CO2)(4)(H2O)(2)], and a linear chain containing one syn-syn-carboxylato dimeric [Cu-2(C2H5CO2)(4)] and its apical position linked by a carboxylate bridge with a unit of [Cu(C2H5CO2)(H2O)]. Cryomagnetic susceptibilities 1 and 2 have been measured over the temperature range 4-300 K. In 1, the spins are coupled through an alternating one-dimensional antiferromagnetic interaction. In 2, the cryomagnetic exchange interaction has been interpreted in terms of a strong antiferromagnetic interaction associated with the two paired dinuclear units of Cu(II)...Cu(II), and one mononuclear Cu(II) unit which complies with a Curie-Weiss law. (C) 1998 Elsevier Science Ltd. All rights reserved.