Synthesis and Structural Characterization of Di-μ-Phenoxo-Bridged Dinuclear Iron(III) Complexes with Ferromagnetic or Weak Antiferromagnetic Coupling

Dinuclear phenoxo-bridged iron(III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H2La), N-salicylidene-2-hydroxy-5-chlorobenzylamine (H2Lb), and N-salicylidene-2-hydroxybenzylamine (H2Lc): [Fe2(La)2(CH3CO2)2] (1), [Fe2(La)2(C6H5CO2)2] (2), [Fe2(La){(CH3)3CCO2}2] (3), [Fe2(La)2{(C6H5O)2PO2}2] (4), [Fe2(La)2(CH3COCHCOCH3)2] (5), [Fe2(Lb)2(CH3CO2)2] (6), and [Fe2(Lc)2(CH3CO2)2] (7), have been synthesized and characterized by measurements of the infrared and electronic spectra as well as the magnetic susceptibilities. Single-crystal X-ray analysis has revealed that all of the complexes are dinuclear iron(III) complexes having a dinuclear iron(III) core bridged by two phenoxo-oxygen atoms of the Schiff-base ligands. The magnetic-susceptibility data show that a ferromagnetic interaction is operative within a dinuclear core in 1–4, 6, and 7 with J values ranging from 0.17(5) to 1.56(15) cm−1, whereas an antiferromagnetic coupling is operative in 5 with a J value of −9.24(6) cm−1. The magnetic properties are discussed in relation to the crystal structures.