ELECTRODEPOSITION OF METAL ALLOY AND MIXED-OXIDE FILMS USING A SINGLE-PRECURSOR TETRANUCLEAR COPPER-NICKEL COMPLEX

Electroreduction of heterotetranuclear complexes (mu(4)-O)L(4)Cu(4-x)N i(x)(H2O)(x)Cl-6 (x = 1-4, L = N,N-diethylnicotinamide) at a Pt electr ode in dimethylsulfoxide leads to deposition of Cu-Ni alloys with code position of Cu(I) oxide, Ni(II) oxide, and Ni(II) hydroxide. The alloy deposition potential is invariant with complex stoichiometry. Alloy N i composition, determined by x-ray diffraction (XRD), increases from 1 2% for x = 1 to 62% for x = 4. The microscopically rough, well-adherin g, continuous films have a natural passivation layer formed by air oxi dation that consists of Ni(OH)(2), NiO, Cu(OH)(2), and Cu2O. X-ray pho toelectron spectroscopy confirmed the bulk film alloy compositions obt ained by XRD. The data revealed complex deposit structures consisting of NiO, Ni(OH)(2), Cu2O, and Cu-Ni alloy giving a mass balance of the metals in the complexes. The Cu2O/Cu-0 ratio is close to unity for the deposit made from the Cu, complex and decreases to zero for the CuNi3 complex. In contrast only half of the Ni(II) centers are deposited as Ni-0 in the Cu-Ni alloy, the balance consisting of 37% NiO and 15% Ni (OH)(2). The constant percentage of Ni as Ni(OH)(2) in all deposits su ggests that it arises from reduction of Ni coordinated water. Mass bal ance indicates O in Cu2O and NiO originates from the mu(4)-O. Smooth v ariations of alloy compositions, metal oxide/metal ratios, and film pa rticle sizes indicate that all the electrode processes involve discret e molecules of the heteropolymetallic complex.