Crystal structure and E.S.R. of 2,2'-Bipyridylium Tris(2,2'-bipyridyl)iron(III) tetraperchlorate

Abstract

The crystal structure of the title compound (C₁₀H₉N₂) [Fe(C₁₀H₈N₂)₃] (ClO₄)₄ has been determined at c. 295 K from diffractometer data and refined by least squares to R 0.056 (7018 reflections with I > 3σ(I)). Crystals are triclinic, Pī, a 16.607(3), b 13.496(3), c 10.254(2) Ǻ, α 101.13(2), β 92.08(2), γ 102.77(1)°, Z 2. The iron atom is surrounded by three bidentate ligands, the six Fe-N distances being equal (<Fe-N> 1.96₃ Ǻ). The monoprotonated bipyridylium cation adopts the unusual cis configuration, with the proton clearly located on one of the nitrogen atoms. The e.s.r. g-tensor is approximately axial (g_|| 1.47₄, g, 2.69₀) but its axes do not coincide with obvious geometric features of the cation.