Syntheses and structural study of trinuclear iron acetates [Fe3O(CH3COO)6(H2O)3]Cl•6H2O and [Fe3O(CH3COO)6(H2O)3][FeCl4]•2CH3COOH

The structure of two trinuclear iron acetates [Fe3O(CH3COO)(6)(H2O)(3)]Cl . 6H(2)O (I) and [Fe3O(CH3COO)(6)(H2O)(3)][FeCl4]. 2CH(3)COOH (II) was determined by X-ray diffraction analysis. Crystals I and II are ionic and belong to the orthorhombic system with parameters a = 13.704(3), b = 23.332(5), c = 9.167(2) Angstrom, R = 0.0355, space group P2(1)2(1)2 for I and a = 10.145(4), b = 15.323(6), c 22.999(8) Angstrom, R = 0.0752, space group Pbc2(1) for II. The complex cation [Fe3O(CH3COO)(6)(H2O)(3)](+) has a mu(3)-O-bridged structure typical for trinuclear iron(III) compounds. As shown by Mossbauer spectroscopy, the iron(III) ions are in the high-spin state. In trinuclear cations, antiferromagnetic exchange interaction takes place between the Fe(III) ions with the exchange parameter J = -26.69 cm(-1) for N (Heisenberg-Dirac-Van Vleck model for D-3h symmetry).