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Issue 10, 1997
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Electrochemistry of the copper–nickel series of heteropolymetallic complexes [(µ4-O){NC5H4[C(O)NEt2 ]-3}4Cu4-x {Ni(H2O)}xCl6 ] (x = 0–4)

Abstract

The electrochemistry of the tetranuclear copper–nickel heteropolymetallic complexes [(µ 4 -O)L 4 Cu 4-x { Ni(H 2 O)} x Cl 6 ] [x = 0–4, L = N,N-diethylnicotinamide (denc)] were studied at a platinum electrode in dimethyl sulfoxide with 0.20 M tetrabutylammonium hexafluorophosphate as supporting electrolyte. At potentials more cathodic than -1.0 V the complexes are electrodeposited as Cu–Ni alloy and metal oxide films and display a complicated set of cyclic voltammographs. The voltammographs of all the Cu-containing complexes show a quasi-reversible redox couple in the potential range 0.250 to -0.450 V vs. Ag–AgPF 6 (0.01 M)–CH 3 CN. As the number of Cu atoms decreases in the complex, the peak currents i pa and i pc decrease proportionally and the peak potential shifts anodically. The cyclovoltammetric (CV) results indicate that electron transfer initially occurs only to the Cu II centres and that the electron-transfer reaction appears to be quasi-reversible. Using steady-state voltammetry at an ultramicroelectrode in combination with chronoamperometry at a microelectrode and exhaustive electrolysis at a Hg-pool electrode, the number of electrons (n) transferred for this initial reduction of the Cu 4 , Cu 3 Ni, Cu 2 Ni 2 and CuNi 3 complexes were 3.1, 2.1, 1.8 and 0.57, respectively. The diffusion coefficient for all the complexes was 2.2(±0.1) × 10 - cm 2 s -1 . The electronic spectrum of the Cu 4 complex taken after exhaustive electrolysis shows that one quarter of the Cu atoms remain in the Cu II form and that the Cu I complex remains stable. Since only a single CV peak results for all of the complexes, the electron transfer is most likely consecutive with very closely spaced E° potentials. A model based on statistically determined electron transfer to Cu II in particular faces is also proposed.

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Article information


J. Chem. Soc., Dalton Trans., 1997, 1739-1746
Article type
Paper

Electrochemistry of the copper–nickel series of heteropolymetallic complexes [(µ4-O){NC5H4[C(O)NEt2 ]-3}4Cu4-x {Ni(H2O)}xCl6 ] (x = 0–4)

B. Workie, C. E. Dubé, L. Aksu, S. P. Kounaves, A. Robbat Jr and G. Davies, J. Chem. Soc., Dalton Trans., 1997, 1739
DOI: 10.1039/A607234H

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