Division of the Effects of Cation Symmetry and Its Packing on the Mixed-Valence State of 1‘,1‘ ‘‘-Bis(2-methylbutyl)-1,1‘ ‘-biferrocenium Triiodide Having Asymmetric Carbon in the Substituent

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Abstract

The effects of the cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed separately by paying attention on the differences between the racemic and (S,S) samples and between the salts from hexane and from dichloromethane in 1‘,1‘ ‘‘-bis(2-methylbutyl)-1,1‘ ‘-biferrocenium triiodide having asymmetric carbon. An (R,S) isomer can sit on the center of symmetry, while (S,S) and (R,R) isomers cannot. Such a difference plays an important role on the mixed-valence state in the samples from dichloromethane but not in the samples from hexane. Both the racemic and (S,S) salts in the disordered state showed the same temperature-dependent mixed-valence state. The disordered state of racemic and (S,S) salts from hexane changed to the ordered state by recrystallization from dichloromethane. The ordered state for (S,S) salts showed a typical temperature-independent trapped-valence state. The packing effect in the present salts appears different from that of the derivatives with long alkyl chain. (S,S)-1‘,1‘ ‘‘-bis(2-methylbutyl)-1,1‘ ‘-biferrocenium triiodide (Fe2C30H38I3) crystallized in a triclinic system with space group P1 and unit cell parameters a = 10.242(1) Å, b = 13.380(2) Å, c = 13.797(1) Å, α = 109.358(6)°, β = 93.015(6)°, γ = 113.214(4)°, and Z = 4. The ordered racemic sample changed to the disordered state in the solid state at room temperature as time proceeded, while the ordered (S,S) sample changed to the disordered state by annealing at high temperature, which were followed by the change of mixed-valence state.

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