New Tetranuclear Cu(II) Complexes: Synthesis, Structure, and Magnetic Properties

The synthesis, structure, and magnetic properties of two new tetranuclear Cu(II) complexes containing N,N,N‘,N‘-tetraethylpyridine-2,6-dithiocarboxamide (S-dept) of formula [Cu2Cl2(μ-S-dept)2][Cu2Cl4(μ-Cl)2] (1) and [Cu2(μ-Cl)2(S-dept)2][CuCl3(EtOH)]2 (2) are reported. Their X-ray crystal structures reveal that the complexes are composed
of anionic and cationic dimers, that in both cases contain the metal centers which interact via Coulombic and/or
hydrogen bonding interactions. In both cases, the Cu centers in the anionic moieties adopt a slightly distorted
tetrahedral geometry whereas for the cationic moieties they adopt a square-pyramidal type of geometry. Magnetic
susceptibility data show that compounds 1 and 2 present an overall antiferromagnetic behavior arising from the
contribution of both anionic and cationic moieties. For 1, the best fit obtained gave J1 = −2.62 ± 0.19 cm-1, J2 =
−19.54 ± 0.47 cm-1, and g2 = 2.164 ± 0.004 cm-1 (R = 8.28 × 10-5) whereas for 2 it gave J1 = 4.48 ± 2.73
cm-1, g1 = 2.20 ± 0.03, J2 = −11.26 ± 2.01 cm-1, and g2 = 2.10 ± 0.03 (R = 1.15 × 10-4). The nature of the
superexchange pathways in 1 and 2 is discussed on the basis of structural, magnetic, and molecular orbital
considerations. Theoretical calculations are performed at the extended Hückel level in order to obtain their molecular
orbitals and energies using their crystallographic data.