Making connections with molecular wires: extending tri-nickel chains with axial cyanide, dicyanamide, and phenylacetylide ligands

New chemistry needed to facilitate the replacement of axial ligands (X) in Ni3(dpa)4X2 complexes (dpa = the anion of dipyridylamine) has been explored and used to replace X = Cl by X = CN, NCNCN, and CCPh. The resulting compounds, 3, 4, and 5, respectively, have been characterized by X-ray crystallography and cyclic voltammetry, inter alia. It is found that both the mean Ni⋯Ni separations (D), and the magnitude of the antiferromagnetic coupling (J) between the terminal, high spin (S = 1) Ni(II) atoms vary in a correlated way, with |J| decreasing with increasing D. The relationship is nearly linear over the available ranges of parameters, suggesting that the coupling may proceed mainly through the central, diamagnetic Ni(II) ion.