Preparation and characterization of the dinuclear complexes [Fe2Cl4L2] and [Fe2Cl4L2]Cl2 (L = 2-(2′-pyridyl)quinoxaline)

The 1:1 reactions of FeCl2 . 4H(2)O and FeCl3 with the biheteroaromatic ligand 2-(2'-pyridyl)quinoxaline (L) were studied in methanol. The new complexes [Fe2Cl4L2] (1) and [Fe2Cl4L2]Cl-2 (2) were isolated and characterized by elemental analyses, conductivity measurements, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, ligand field, Fe-57 Mossbauer) techniques. The X-ray crystal structure of 1 consists of two Fe-II centres bridged by two chloro ligands, with a terminal chloride and a chelating molecule of L completing five-coordination at each metal. The geometry at iron is distorted trigonal bipyramidal with the bridging chlorides occupying apical and equatorial sites of each Fe-II atom. A five-coordinate dinuclear structure is also assigned for the cation of complex 2. All data are discussed in terms of the nature of bonding and known or assigned structures. (C) 1998 Elsevier Science Ltd. All rights reserved.