The reaction of LFeCl3 (L = N,N′,N″-trimethyl-1,4,7-triazacyclononane) with Na2SO4, Na2SO3/NaClO4, and Na2SeO3/NaClO4 in aqueous solution affords the binuclear oxo bridged complexes [L2Fe2(μ-Ο)(μ-SΟ4)2]·3Η2Ο (1), [L2Fe2(μ-O)(μ-SO3)2]·5/3NaClO4·(H2O)3.67 (2), [L2Fe2(μ-O)(μ-SeO3)2](NaClO4)2.75·5H2O (3). The reaction of LFeCl3 in dry methanol with Na2SO4 yields yellow crystals of [L2Fe2(μ-SO4)3] · 2 H2O (4). The crystal structures of 1 and 2 have been determined by X-ray crystallography. Crystals of 1, 2, and 3 consist of neutral, binuclear μ-oxo bridged diiron(III) complexes which contain two additional O,O′-coordinated sulfato, sulfito, and selenito bridging ligands, respectively. The high spin ferric ions in 1, 2, and 3 are strongly intramolecularly antiferromagnetically spin exchange coupled with J values of —97(1), -104(2), and —104(2) cm-1 (H = —2JŜ,·Ŝ2, S1 = S2 = 5/2), respectively. 4 contains three μ-sulfato bridges between two FeIII ions. Only a very weak antiferromagnetic coupling has been detected (J = —5.5(5) cm-1). Complex 1 serves as a model compound for the diiron(III) complex of the sulfate treated, oxidized form of the biomolecule uteroferrin.
Bioanorganische Modellkomplexe für Metalloproteine des Eisen(III): Synthese, Kristallstrukturen und Magnetismus der zweikernigen Komplexe [L2Fe2III(µ-O)(μ-SO4)2] · 3 H2O und [L2Fe2III(μ-O)(μ-SO3)2] · 5/3 NaClO4 · (H2O)3.67 (L = N,N′N″-Trimethyl-1,4,7-triazacyclononan) / Bioinorganic Model Complexes for Metalloproteins of Iron(III): Syntheses, Crystal Structures, and Magnetism of the Binuclear Complexes [L2Fe2III(μ-O)(μ-SO4)2]·3 Η2O and [L2Fe2III(μ-O)(μ-SO3)2] · 5/3 NaClO4 · (H2O)3.67 (L = N,N′,N″-Trimethyl-1,4,7-triazacyclononane)