Ferrocenyl-derived face-capping ligands: syntheses and molecular structures of [(FcTt)Cu]4 and [FcTt]2M (M = Fe, Co, Ni; FcTt = ferrocenyltris((methylthio)methyl)borate)

The synthesis and characterization of a ferrocenyl-derived tridentate ligand, ferrocenyltris((methylthio)methyl)borate (FcTtP⁻), and its representative metal complexes, [(FcTt)Cu]₄ and [FcTt]₂M (M = Fe, Co and Ni), are reported. The M = Fe complex exhibits spin-crossover behavior with a μ_eff = 1.19 μ_B at 25°C. The low-spin Co(II) derivative (1.88 μ_B) exhibits a characteristic axial electron paramagnetic resonance (EPR) spectrum, g_av = 2.13, A = 53 G and A_¦ = 43 G. The [FcTt]₂M complexes display reversible two-electron redox processes assigned to ligand-centered events about 200 mV negative of the ferrocene-ferrocenium couple. [(FcTt)Cu]₄ and [FcTt]₂Ni have been characterized by X-ray diffraction. X-ray data for [(FcTt)Cu]₄: monoclinic space group C2/c, with a = 24.3747(3) Å, b = 20.0857(2) Å, c = 17.2747(4) Å, β = 95.843(1)°, V = 8413.5(3) ų, and Z = 4; [FcTt]₂Ni: monoclinic space group C2/c, with a = 12.6220(3) Å, b = 11.6002(3) Å, c = 25.0125(7) Å, β = 94.067(1)°, V = 3653.1(2) ų, and Z = 4.