Syntheses and characterisation of mono- and di-nuclear iron(III) complexes of 1,4,7-triazacyclononane-N-acetate (L). Crystal structures of [FeCl₂L] and [Fe₂(µ-O)(µ-O₂CMe)L₂]ClO ₄· NaClO₄·2H₂O 

Abstract

The macrocycle 1,4,7-triazacyclononane-N-acetate (L) reacted with FeCl₃·6H₂O in water to form the monomeric complex [FeCl₂L] 1. Hydrolysis of 1 in the presence of an excess of sodium acetate and sodium perchlorate yielded the binuclear complex [Fe₂(µ-O)(µ-O₂CMe)L₂]ClO₄ ·NaClO₄·2H₂O 2. Complexes 1 and 2 have been characterised by X-ray crystallography. In 1 the Fe^III is surrounded by a distorted-octahedral array of one fac-co-ordinated triamine ring, one monodentate carboxylato group and two chloride ligands. Complex 2 consists of a µ-oxo-µ-acetato-diiron(III) core with the distorted octahedral co-ordination sphere about each Fe^III being completed by the ligand L. A sodium ion, with distorted trigonal-bipyramidal stereochemistry, bridges between the co-ordinating carboxylate oxygens of the terminal ligands. Complex 2 exhibits spectroscopic features and magnetic properties similar to those of other µ-oxo-diiron(III) complexes as well as metalloproteins incorporating a µ-oxo-diiron(III) unit at their active sites.

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