Synthesis, molecular structure and magnetic properties of [Fe6(μ3-O)2(OPri)2(μ-OPri)6(O2CPh)2(μ-O2CPh)4]

The reaction of an Fe(III) oxo-benzoate species (1) with Al(OR)(3) (R = Pr-i, Bu-sec) yields the hexanuclear derivatives [Fe-6(mu(3)-O)(2)(OR)(8)(O2CPh)(6)] (R = Pr-i (2): R = Bu-sec (3)) which consist of planar Fe-4(mu(3)-O)(2) units. formed by two Fe-3(mu(3)-O) groupings having common Fe(III) atoms. with further Fe(OR)(4) entities. each attached by three bridging OR groups to Fe-3(mu(3)-O) units, above and below the Fe, plane. The OPri complex has an S = 3 magnetic ground state and shows unusual temperature dependence of mu(eff) below 60 K because of the complex series of low lying spin states generated by six high-spin Fe(III) centres undergoing antiferro- and ferromagnetic intracluster coupling. The Mossbauer spectrum at 81 K supports the presence of three inequivalent Fe sites in the molecule, as noted in the crystal structure. (C) 2002 Elsevier Science B.V. All rights reserved.