Binuclear Metal Complexes. IL. Synthesis, ESR, and Electrochemical Properties of Strati-bis Copper(II)–Nickel(II) Complexes

Abstract
Strati-bis copper(II)–nickel(II) complexes, CuNi(R-sata) and CuNi(R-sacta) (R=H, 5-Me, 5-Br), have been prepared, where H4(R-sata) and H4(R-sacta) denote 1,2,3,4-tetrakis(R-salicylideneamino)-2,3-dimethylbutane and 1,2-bis(R-salicylideneamino)-1,2-bis(R-salicylideneaminomethyl)cyclohexane, respectively. ESR spectra of the complexes (frozen chloroform solution at liquid nitrogen temperature) showed a tetragonal pattern with a hyperfine coupling constant A⁄⁄ smaller than that of the relevant mononuclear copper(II) complex. Based on cyclic voltammetry and differential pulse polarography, it was shown that the Cu(II)→Cu(I) reduction occurs at a higher potential than that of the mononuclear reference complex. The ESR and electrochemical properties have been interpreted in terms of the stacking of the CuN2O2 and NiN2O2 planes and hence the electron delocalization over the whole molecule through the ligand π-system.
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