Heterobimetallic complexes based on [(Tp)Fe(CN)3]- :: Syntheses, crystal structures and magnetic properties

With the anionic precursor [(Tp)Fe-III (CN)(3)](-) [1; Tp: hydro-tris (pyrazolyl)borate] as a building block, two trinuclear complexes, [(Tp)(2)Fe-2(III)(CN)(6)Mn(CH3OH)(4)](.)2CH(3)OH (2), [(Tp)(2)Fe-2(III)(CN)(6)Ni(cyclam)](.)2H(2)O (3; cyclam: 1,4,8,11-tetraazacyclotetradecane) and a one-dimensional polymer, [(Tp)Fe-III(CN)(3)Cu(dien)](ClO4H2O)-H-. (4; dien: diethylenetriamine), have been synthesized and structurally characterized. In complex 2, each of the two [(Tp)Fe(CN)31- units binds through one of its three cyanide groups to a central [Mn(CH3OH)(4)](2+) core. In complex 4, a zigzag chain is formed by combining [TpFe(CN)(3)](-) and [Cu(dien)](2+) fragments alternately through cyano bridges. The magnetic properties of complexes 2-4 have been investigated in the temperature range 2-300 K. A weak antiferromagnetic interaction between the Mn-II and Fe-III ions has been found in complex 2. The magnetic data of 2 can be fitted with the isotropic Hamiltonian H = -2J((S) over cap (.)(1)(S) over cap (2) + (S) over cap (.)(2)(S) over cap (3)) - 2J' (S) over cap (.)(1)(S) over cap (3,) where J and J' are the intramolecular exchange coupling parameters between adjacent and peripheral spin carriers, respectively. This leads to values of J = -2.19 cm(-1) and g = 2.13. The same fitting method was applied to complex 3 to give values of J = 17.2 cm(-1) and g = 2.37, showing that there is a ferromagnetic interaction between the Fe-III and Ni-II ions. The 1-D chain of 4 is treated as alternating uniform Fe-Cu dimers with different intradimeric (J(d)) and interdimeric (J(c)) exchange constants, leading to Jd = 10.9 cm(-1), J(c) = 1.29 cm(-1) and g = 2.54. (C)Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)