Electrodeposition of Metal Alloy and Mixed Oxide Films Using a Single‐Precursor Tetranuclear Copper‐Nickel Complex

Abstract

Electroreduction of heterotetranuclear complexes at a Pt electrode in dimethylsulfoxide leads to deposition of Cu‐Ni alloys with codeposition of Cu(I) oxide, Ni(II) oxide, and Ni(II) hydroxide. The alloy deposition potential is invariant with complex stoichiometry. Alloy Ni composition, determined by x‐ray diffraction (XRD), increases from 12% for to 62% for . The microscopically rough, well‐adhering, continuous films have a natural passivation layer formed by air oxidation that consists of , , , and . X‐ray photoelectron spectroscopy confirmed the bulk film alloy compositions obtained by XRD. The data revealed complex deposit structures consisting of , , , and Cu‐Ni alloy giving a mass balance of the metals in the complexes. The ratio is close to unity for the deposit made from the complex and decreases to zero for the complex. In contrast only half of the Ni(II) centers are deposited as in the Cu‐Ni alloy, the balance consisting of 37% and 15% . The constant percentage of Ni as in all deposits suggests that it arises from reduction of Ni coordinated water. Mass balance indicates O in and originates from the μ4‐O. Smooth variations of alloy compositions, metal oxide/metal ratios, and film particle sizes indicate that all the electrode processes involve discrete molecules of the heteropolymetallic complex.