Hexacoordinate high-spin Fe(iii) complexes composed of a pentadentate amino-type ligand and pseudohalido coligands

Abstract

A new series of Fe(III) mononuclear complexes of the [Fe(L^am)(X)] type {where X = Cl (1), NCSe (2), NCS (3), N₃ (4), and NCO (5)} have been prepared and characterized in detail. An untraditional pentadentate amino-ligand L^am was prepared by a reductive amination of an imino precursor L^im. The DC magnetic data confirm a high-spin state for 1–5 over the whole temperature scale; however, some significant differences in the magnetic data are observed. The spin Hamiltonian with the isotropic Zeeman term has been utilized for describing the zero-field splitting (ZFS) in 2, 3 and 5. In 1 and 4, the formation of exchange coupled dimers is evident with the isotropic exchange coupling of antiferromagnetic nature. The zero-field splitting D parameters adopt small values: 1.15 (1), −0.74 (2), −1.7 (3), 1.5 (4) and −0.62 cm⁻¹ (5) which match the theoretical predictions.