A novel seven-coordinate dinuclear iron(III) complex, [Fe 2 (O) (NO 3 ) 4 (bpy) 2 ] (1) (bpy = 2,2 -bipyridine), with a linear Fe-O-Fe bridge has been prepared and characterized by X-ray crystallography and magnetic susceptibilities. Each iron atom of 1 has a distorted pentagonal-bipyramidal geometry in which four oxygen atoms of two bidentate nitrato ligands and one nitrogen atom of bpy form the pentagonal plane. The other nitrogen atom of bpy and the bridging oxo ion occupy the axial positions. The iron-iron and iron-oxo distances are 3.550(3) and 1.775(1) 9, respectively. The - J value of 104 cm - 1 for 1 indicates the presence of an antiferromagnetic interaction due to superexchange coupling between two iron(III) ions via an oxo-bridge.