Modular bimetallic complexes with a sulfonamido-based ligand

Abstract

A series of bimetallic complexes prepared with the ligands N,N,N′,N′-tetramethylethane-1,2-diamine (TMEDA) and N,N′,N′′-[2,2′,2′′-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]³⁻) is described. Four diiron compounds of the formulation (TMEDA)Fe^II(X)-(μ-OH)-Fe^IIIMST were prepared, in which the X⁻ ligands are the anions OTf⁻, Br⁻, SCN⁻, or N₃⁻. Additionally, two heterobimetallic compounds of the formulation (TMEDA)M^II(OTf)-(μ-OH)-Fe^IIIMST (M^II = Co^II or Ni^II) were synthesized. All these compounds have similar spectroscopic and structural properties. The diiron compounds exhibit perpendicular-mode electron paramagnetic resonance spectra consistent with S = 1/2 spin ground states, which is expected for high-spin Fe^II and Fe^III centres that are antiferromagnetically coupled. The heterobimetallic (TMEDA)Ni^II(OTf)-(μ-OH)-Fe^IIIMST complex had a spin state of S = 3/2 that also resulted from antiferromagnetic coupling between the high-spin Ni^II and Fe^III centres. The modularity of this system is further demonstrated by the substitution of the TMEDA ligand with ethylenediamine (en); for this species two equivalents of en coordinate to the Fe^II centre to form [(en)₂Fe^II-(μ-OH)-Fe^IIIMST]OTf. These results demonstrate that a modular bimetallic system has been developed in which the key components can be modified.