Enhancing the stability of trinickel molecular wires and switches: Ni(3)(6+)/Ni(3)(7+)

This paper describes in detail four new compounds that contain extended metal atom chains (EMACs) of three nickel atoms wrapped by either di(2-pyridyl)amide (dpa) or the new homologous ligand with an ethyl group at the para position of each pyridyl group, depa, and compares them to the precursor Ni(3)(dpa)(4)Cl(2) (1) and the oxidized and rather unstable Ni(3)(dpa)(4)(PF(6))(3) (2). The new molecules are Ni(3)(depa)(4)Cl(2) (3), Ni(3)(depa)(4)(PF(6))(3) (4), Ni(3)(dpa)(4)(CH(3)CN)(2)](PF(6))(2) (5), and Ni(3)(depa)(4)(CH(3)CN)(2)](PF(6))(2) (6). These compounds are fully described as to preparation, elemental composition, structure, infrared spectra, (1)H NMR spectra (where possible), electrochemistry, magnetic susceptibility, and an EPR spectrum for 4. The effects of (a) introducing the ethyl substituents on the ligands, (b) replacing axial anions by neutral axial ligands, and (c) oxidizing the Ni(3) chains are reported and discussed. The point of major interest is how oxidation profoundly alters the electronic structure of the EMAC.