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) A?, b = 20.0857(2) A?, c = 17.2747(4) A?, β = 95.843(1)°, V = 8413.5(3) A?³, and Z = 4; FcTt]₂Ni: monoclinic space group C2/c, with a = 12.6220(3) A?, b = 11.6002(3) A?, c = 25.0125(7) A?, β = 94.067(1)°, V = 3653.1(2) A?³, and Z = 4.