Structural studies in the iron(III)/chloride/α,α'-diimine system. II. Ionic derivatives of stoichiometry FeCl₃(phen,bpy)_1,1.5

Abstract

The crystal structures of the 1 : 1 adducts of FeCl₃ with 2,2'-bipyridine (bpy) (1) and 1,10-phenanthroline (phen) (2), as recrystallized from nitromethane, have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by least squares to residuals of 0.038 and 0.032 for 1341 and 3968 'observed' reflections; the result for (2) is a redetermination. Crystals of (1) are orthorhombic, Pbnb, a 15.013(4), b 13.510(5), c 12.471(3) Ǻ, Z 4. Crystals of (2) are triclinic, P1, a 15.823(5), b 11.021(5), c 8.200(3) Ǻ, α 80.27(3), β 76.78(3), γ 89.64(3)°, Z 2. Both complexes haw the stoichiometry (FeCl₃)₁(bpy,phen)₁, but are formulated as cis-[Fe(bpy,phen)₂Cl₂] [FeCl₄]; in both compounds, the Fe-N distance is c. 2.2₀, (trans to Cl), 2.1, Ǻ(cis to Cl), while Fe-Cl, c. 2.2, Ǻ, is short. The structure determinations of Fe₂Cl₆(phen,bpy)₃ as [Fe(phen)₂Cl₂]⁺ [Fe(phen)Cl₄]^- (3) and [Fe(bpy)₂Cl₂]⁺ [Fe(bpy)Cl₄]^- (4) are also reported. Compound (3) (from acetonitrile solution) is triclinic, P1, a 16.502(5), b 11.857(3), c 10.653(3) Ǻ, α 84.92(2), β 72.66(2), γ 74.80(2)°, Z 2, and was refined to a residual of 0.034 for 5540 'observed' reflections. The cation geometry is similar to that of (2); in the anion, the two Fe-CI bonds trans to each other are long [2.377(1) and 2.365(1) Ǻ] while those trans to the Fe-N bonds are short [2.287(1) and 2.318(1) Ǻ]. Fe-N distances are 2.216(3) and 2.220(3) A. Compound (4) (as its nitromethane solvate) is also triclinic, P1, a 14.480(7), b 12.645(5), c 10.678(4) Ǻ, α 95.68(3), β 109.21(3), γ 9258(3)°, Z 2; a residual of 0.042 was obtained for 4962 'observed' reflections. Cation and anion metal geometries are similar to those of (3).