Di- and tetra-bridged diiron(II) complexes with four terphenyl-derived carboxylates and two water molecules

New diiron(II) complexes having ligated water molecules were prepared and characterized by X-ray crystallography, IR spectroscopy and cyclic voltammetry. The compound [Fe-2(OH2)(2)(mu-O2CAr4F-Ph)(2)(O2CAr4F-Ph)(2)(THF)(2)] (1), where -O2CAr4F-Ph is 2,6-di(p-fluorophenyl)benzoate, has two distorted trigonal bipyramidal Fe(II) centers linked by two sterically hindered carboxylate ligands. The related molecules, [Fe-2(mu-OH2)(2)(mu-O2CArTol)(2)(O2CArTol)(2)(THF)(2)] (2) and [Fe-2(mu-OH2)(2)(mu-O2CArTol)(2)(O2CArTol)(2)-(4-(BuC5H4N)-Bu-t)(2)] (3), where (-O2CArTol) is 2,6-di-(p-tolyl)benzo ate and 4-(BuC5H4N)-Bu-t is 4-tert-butylpyridine, contain a tetra-bridged diiron(II) core with a central Fe-2(OH2)(2) planar quadrilateral. Vibrational spectroscopic and electrochemical measurements reveal that the ligated water molecules of 3 are in equilibrium between the bound and free forms. (C) 2004 Elsevier Ltd. All rights reserved.