Abstract
Nickel(II) complexes with three new vic‐dioxime reagents, N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)phenylglyoxime (L~1~H~2~), N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L~2~H~2~) and N,N′‐bis(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L~3~H~2~), have been prepared. Mononuclear nickel(II) complexes with a metal/ligand ratio of 1:2 were prepared using Ni(II) salt. All these nickel(II) complexes are nonelectrolytes as shown by their molar conductivities (Λ~M~) in DMF solution at 10^−3^ M concentration. The ligands are soluble in common solvents such as DMSO, DMF, CHCl~3~, and C~2~H~5~OH. The ligands and their Ni(II) complexes were characterized by elemental analyses, FT‐IR, UV‐visible, ^1^H NMR, ^13^C NMR, magnetic susceptibility measurements, cyclic voltammetry, and molar conductivities (Λ~M~). The cyclic voltammetric measurements show that [Ni(L~1~H)~2~] and [Ni(L~2~H)~2~] complexes exhibit almost similar electrochemical behavior, with two reduction and two oxidation processes based on either metals or oxime moities, while [Ni(L~3~H)~2~⋅2H~2~O] complex displays irreversible, with one reduction and one oxidation processes based on oxime moity. This main difference could be attributed to the highly polarized [Ni(L~3~H)~2~⋅2H~2~O] complex that has four carboxylate groups attached to piperidine on the oxime moieties. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:657–663, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20357