The synthesis and characterization of potassium 2,2-bipyridinetetranitroruthenate

We report a convenient synthesis of K-2[Ru(bpy)(NO2)(4)] via the thermal di splacement of benzene from, [(Bz)Ru(bpy)Cl]Cl (Bz =eta (6)-C6H6; bpy = 2,2' -bipyridine) by nitrite ion in methanol, solution. K-2[Ru(bpy)(NO2)(4)] has been fully characterized by elemental analysis, X-ray crystallography, and H-1 NMR, IR, UV-vis, and emission spectroscopy. Reaction of K-2[Ru(bpy)(NO 2)(4)] with pyridine under mild or forcing conditions produces fac-K[Ru(bpy )(NO2)(3)(py)] and cis-[Ru(NO2)(2)(bpy)(PY)(2)] (py = pyridine), respective ly. We report full characterization data for these compounds, including cry stal structures. The d pi (Ru) --> pi*(bpy) charge-transfer band in the ele ctronic spectra of K-2[Ru(bpy)(NO2)(4)] and fac-[Ru(bpy)(NO2)(3)(py)] displ ays a significant solvent dependence. The energy of the absorption band cor relates linearly with the Gutmann solvent acceptor number. The solvatochrom ic response of these nitro complexes is essentially identical to that of th e analogous cyanide complexes, indicating that the mechanism previously pro posed to explain the solvatochromism of the cyanide complexes may need to b e reexamined.