THE ELECTROCHEMICAL-BEHAVIOR OF MIXED NICKEL(II)-CHELATES IN NONAQUEOUS SOLVENTS

The electrochemical reduction of solvatochromic and thermochromic mixed chelates of the type Ni(β- dik)(diam)+, where β-dik represents a series of substituted β-diketonates and diam represents substituted diamines has been investigated at different temperatures in different solvents (DCE, An, Ac, DMF and DMSO). The observed polarographic two-electron reduction of Ni(II) on the Hg-electrode is irreversible in all solvents studied. Polarographic prewaves are observed which are interpreted in terms of kinetically and diffusion controlled electrode processes. E1, 2is shifted to more negative potentials by increasing donor number (DN), decreasing temperature and the presence of electron-donating substituents. The temperature dependence of the Ni reduction potentials yielded two groups of solvents. This is interpreted as being due to different electrode kinetics involving diffusion and kinetically controlled rate-determining steps. The two groups further refer to a different stereochemistry of the solvated complexes in DCE, An and Ac on the one hand, and DMF and DMSO on the other. The results are discussed in terms of the extended donor–acceptor concept and related to results from UV, VIS and IR spectroscopy. © 1992, Taylor & Francis Group, LLC. All rights reserved.