In this work, a new synthesis pathway to the ligand, N,N'-dimethyl-N,N'-bis(2-thiophenolate)ethylenediamine(2-) (L-N2SAr2(2-)), has been developed. This new procedure offers improved yields with greater reproducibility compared to a published route. A novel pentacopper complex, [[(L-N2SAr2)Cu]3Cu2], was prepared from either Cu2O, Cu(acac)2 or CuI, and its structure was determined by X-ray diffraction. Its cyclic voltammogram showed a highly reversible reduction to an all cuprous state at a potential of -0.46 volts vs. Ag/AgCl. The reduced form, [[(L-N2SAr2)Cu]3Cu2]1-, has been examined for reactivity with sulfur atom donors but yields only charge-neutral starting material in an apparent, rapid outer-sphere oxidation. A reversible oxidation is also observed by cyclic voltammetry but with a clearly diminished current amplitude compared to the reduction wave. Chemical oxidation of a small sample of [[(L-N2SAr2)Cu]3Cu2] with [Cp2Fe][PF6] readily yielded a dimeric dication, identified structurally. Three absorption bands are found in its UV-vis spectrum, and spectroelectrochemistry showed that a peak at 345 nm disappears when the complex is re-reduced. The unpaired electron in [[(L-N2SAr2)Cu]3Cu2] is found to be coupled to one 63,65Cu nucleus and to two 14N nuclei by EPR, which means the CuII ion is coordinated to one N2S2 ligand and not located on the C3 axis. Reaction of L-N2SAr2(2-) with [Cu(N≡CMe)4][PF6] produced the hexacopper species [[(L-N2SAr2)Cu]3Cu2[Cu(N≡CMe)]]+, which is related to [[(L-N2SAr2)Cu]3Cu2] by insertion of a [Cu(N≡CMe)]+ fragment along one equatorial edge of the Cu5 trigonal bipyramid.

Synthesis, structures and properties of copper complexes with diaminobis(thiolato) ligands

255th National Meeting (2018)

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