Heterobimetallic complexes based on [(Tp)Fe(CN)(3)](-) : Syntheses, crystal structures and magnetic properties
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abstract
With the anionic precursor [(Tp)FeIII(CN)3] - [1; Tp: hydrotris(pyrazolyl)borate] as a building block, two trinuclear complexes, [(Tp)2FeIII2(CN) 6Mn(CH3OH)4]2CH3OH (2), [(Tp)2FeIII2(CN)6Ni(cyclam)] 2H2O (3; cyclam: 1,4,8,11-tetraazacyclotetradecane) and a one-dimensional polymer, [(Tp)FeIII(CN)3Cu(dien)]ClO 4H2O (4; dien: diethylenetriamine), have been synthesized and structurally characterized. In complex 2, each of the two [(Tp)Fe(CN)3]- 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 MnII and FeIII ions has been found in complex 2. The magnetic data of 2 can be fitted with the isotropic Hamiltonian = -2J(112 + 23) - 2J 13, 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 FeIII and NiII ions. The 1-D chain of 4 is treated as alternating uniform Fe-Cu dimers with different intradimeric (Jd) and interdimeric (Jc) exchange constants, leading to Jd = 10.9 cm-1, Jc = 1.29 cm-1 and g = 2.54. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
