The binuclear complex [Ni-2(L)(MeCN)(2)](3+) (L2- = compartmental macrocycle incorporating imine N and thiolate S donors) has a Ni-III center bridged via two thiolate S-donors to a diamagnetic Ni-II center. The ground-state has dominant 3d(z2)(1) character similar to that observed for [NiFe] hydrogenases in which Ni-III is bridged via two thiolate donors to a diamagnetic center (Fell). The system has been studied by X-ray crystallography and pulse EPR, ESEEM, and ENDOR spectroscopy in order to determine the extent of spin-delocalization onto the macrocycle L2-. The hyperfine coupling constants of six nitrogen atoms have been identified and divided into three sets of two equivalent nitrogens. The most strongly coupled nitrogen atoms (a(iso) similar to 53 MHz) stem from axially bound solvent acetonitrile molecules. The two macrocycle nitrogens on the Ni-III side have a coupling of a(iso) similar to 11 MHz, and those on the Ni-II side have a coupling of a(iso) similar to 1-2 MHz. Density functional theory (DFT) calculations confirm this assignment, while comparison of the calculated and experimental N-14 hyperfine coupling constants yields a complete picture of the electron-spin density distribution. In total, 91% spin density is found at the Ni-III of which 72% is in the 3d(z2) orbital and 16% in the 3d(xy) orbital. The Ni-II contains -3.5% spin density, and 7.5% spin density is found at the axial MeCN ligands. In analogy to hydrogenases, it becomes apparent that binding of a substrate to Ni at the axial positions causes a redistribution of the electron charge and spin density, and this redistribution polarizes the chemical bonds of the axial ligand. For [NiFe] hydrogenases this implies that the H-2 bond becomes polarized upon binding of the substrate, which may facilitate its heterolytic splitting.