Two cyano-bridged heterotrinuclear complexes built from [(Tp)Fe(CN) 3] − (Tp = hydrotris(pyrazolyl)borate): synthesis, crystal structures and magnetic properties

Abstract

Using an anionic precursor [(Tp)Fe III(CN) 3] − ( 1) as a building block, two cyano-bridged centrosymmetric heterotrinuclear complexes, [ ( Tp ) 2 Fe 2 III ( CN ) 6 Mn II ( C 2 H 5 OH ) 4 ] · 2 C 2 H 5 OH ( 2) and [ ( Tp ) 2 Fe 2 III ( CN ) 6 Ni ( en ) 2 ] ( 3) (en = ethylenediamine), have been synthesized and structurally characterized. In each complex, [TpFe(CN) 3] − acts as a monodentate ligand toward a central [Mn(C 2H 5OH) 4] 2+ or [Ni(en) 2] 2+ core through one of its three cyanide groups, the other two cyanides remaining terminal. The intramolecular Fe–Mn and Fe–Ni distances are 5.2354(4) and 5.0669(11) Å, respectively. The magnetic properties of complexes 2 and 3 have been investigated in the temperature range of 2.0–300 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 ˆ = - 2 J ( S ˆ 1 · S ˆ 2 + S ˆ 2 · S ˆ 3 ) - 2 J ′ S ˆ 1 · S ˆ 3 where J and J′ are the intramolecular exchange coupling parameters between adjacent and peripheral spin carriers, respectively. This leads to values of J = −1.37 cm −1 and g = 2.05. The same fitting method is applied to complex 3 to give values of J = 1.2 cm −1 and g = 2.25, showing that there is a ferromagnetic interaction between the Fe(III) and Ni(II) ions.