New penta-nuclear and hepta-nuclear iron(II, III) complexes with ferrocenedicarboxylic acid

The reaction of [Fe3EuO2(O2CCCl3)(8)(H2O)(THF)(3)] or [Fe2CaO(O2CCCl3)(6)(THF)(4)] and [Fe3O(O2CCMe3)(6)-(H2O)(3)]NO3 with 1,1'-ferrocenedicarboxylic acid (fcdcH(2)) yielded penta- and hepta-nuclear [Fe4O2(O2CCCl3)(6)(fcdc)(THF)(2)(H2O)(2)] and [Fe6O2(OH)(2)(O2CCMe3)(10)(fcdc)(H2O)(2)], respectively, which are the first X-ray structurally characterized clusters comprising Fe(III) and the ferrocenedicarboxylic organometallic ligand. Variable-temperature solid-state magnetic susceptibility measurements in the temperature range 1.8-300 K were carried out, and for both complexes a predominantly antiferromagnetic exchange interaction between the metal centres was observed. Mossbauer investigations show the presence of different environments for the Fe(III) atoms and confirm that no electron-transfer from Fe(II) of the ferrocene unit to Fe(III) of the central core occurs. (c) 2009 Elsevier Ltd. All rights reserved.