Syntheses and characterisation of mono- and di-nuclear iron(III) complexes of 1,4,7-triazacyclononane-N-acetate (L). Crystal structures of [FeCl(2)L] and [Fe-2(mu-O)(mu-O(2)CMe)L(2)]ClO4 center dot NaClO4 center dot 2H(2)O

The macrocycle 1,4,7-triazacyclononane-N-acetate (L) reacted with FeCl3 . 6H(2)O in water to form the monomeric complex [FeCl(2)L] 1. Hydrolysis of 1 in the presence of an excess of sodium acetate and sodium perchlorate yielded the binuclear complex [Fe-2(mu-O)(mu-O(2)CMe)L(2)]ClO4 . NaClO4 . 2H(2)O 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 mu-oxo-mu-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 coordinating carboxylate oxygens of the terminal ligands. Complex 2 exhibits spectroscopic features and magnetic properties similar to those of other mu-oxo-diiron(III) complexes as well as metalloproteins incorporating a mu-oxo-diiron(III) unit at their active sites.