Hiroshi NAKAJIMA, Hirotaka NAGAO and Koji TANAKA
[J. Chem. Soc. Dalton Trans. 1405 (1996)]
Both [Ru(bpy)2((eta)1-napy)(CH3CN)](PF6)2 ([1]-(PF6)2) and [Ru(bpy)2((eta)2-napy)](PF6)2 ([2](PF6)2) (bpy = 2,2'-bipyridine, napy = 1,8-naphthyridine) were prepared, and thier crystal structures were determined by X-ray analysis. Crystal data for [1](PF6)2: triclinic, space group P1 with Z = 2 in a unit of dimension, a = 13.389(5), b = 13.590(2) and c = 10.577(2) Å, a = 104.19(2), b = 109.47(2) and c = 76.48(2)°; for [2](PF6)2: orthorhombic, space group Pbcn with Z = 2 in a unit of dimension, a = 12.497, b = 15.085 and c = 17.594 Å The crystal structure of [1]2+ displays an octahedral coordination with monodentate napy, acetonitrile and two chelating bpys. Despite the inequivalency of two nitrogens of napy of [1]2+ in the solid state, 1H-NMR spectra of [1]2+ in aromatic region resembles that of [2]2+ in a wide-range of -90 to 60 °C, which implies dynamic behavior of napy in [1]2+ in solutions (Scheme 1). Both [1]2+ and [2]2+ undergo an irreversible reduction at -0.98 V (vs. Ag|AgCl) in DMF, and the process gradually becomes a reversible redox reaction on raising temperature up to 30 °C. EPR spectra of [1]+ revealed that one-electron reduction of [1]2+ takes place in the napy localized orbital without an appreciable increase in the electron density on one of the nitrogen of napy. The distinct inequivalence in the charge density between two nitrogen atoms of singly reduced napy results in stabilization of the N rather than N, N' co-ordination mode.