A series of nickel(parallel to) complexes with polydentate aminopyridine ligands N,N,N'-tris-[2-(2'-pyridyl)ethyl]ethane-1,2-diamine (L1), N,N,N'-tris-[2-(2'-pyridyl)ethyl]-N'-methylethane-1,2-diamine (L2), and N,N'-bis-[2-(2'-pyridyl)ethyl]-N,N'-dimethylethane-1,2-diamine (L3) were synthesized and characterized by elemental analysis and spectroscopic methods. Single-crystal X-ray diffraction studies showed that the Ni(parallel to) ions have five-coordinate square-pyramidal geometry in [NiL2](ClO4)(2), similar to that previously found in [NiL1](ClO4)(2)(CH3NO2)-C-. (Hoskins, B. F.; Whillans, F. D. J. Chem. Soc., Dalton Trans, 1975, 657), and square-planar geometry in [NiL3](ClO4)(2). All three nickel(parallel to) complexes are reduced by sodium borohydride or sodium amalgam in organic solvents to nickel(l) species, which were identified by highly anisotropic EPR spectra at 100 K: g(1) = 2.239, g(2) = 2.199, and g(3) = 2.025 for [NiL1](+); g(parallel to) = 2.324 and g(perpendicular to) = 2.079 for [NiL2](+) and [NiL3](+). Cyclic voltammetry of the nickel(parallel to) complexes in acetonitrile exhibited reversible reduction waves at -1.01 V for [NiL1](2+), -0.91 V for [NiL2](2+), and -0.83 V for [NiL3](2+) versus SCE, potentials which are significantly less negative than those of most previously characterized Ni(parallel to) complexes with nitrogenonly donor atoms. Complexes [NiL1](2+) and [NiL2](2+) showed high catalytic activity in the electroreduction of 1,2-trans-dibromocyclohexane to cyclohexene.