A new core topology in hexanuclear iron(III) carboxylate chemistry: [Fe6O3(O2CMe)9(OEt)2(bpy)2](ClO4) †

Abstract

The structural, spectroscopic, and magnetochemical characteristics of a new hexanuclear iron-oxo complex are reported. [Fe6O3(O2CMe)9(OEt)2(bpy)2]ClO4·¼EtOH·¼H2O (3·¼EtOH·¼H2O) crystallizes in the triclinic space group P with a = 11.524(1) Å, b = 15.865(2) Å, c = 17.029(2) Å, α = 65.92(1)°, β = 81.49(1)°, γ = 76.40(1)°, V = 2758 Å3, and Z = 2. The [Fe6O3]12+ core of the cation contains an arrangement of six iron atoms not previously seen in iron-oxo compounds. In this arrangement, two [Fe3O]7+ triangular units are bridged by a distorted tetrahedral oxide ion. 1H- and 2H-NMR spectra are reported for two [Fe6O3]12+ complexes, 3 and the 4,4′-Me2bpy analog 4, as well as CD3CO2− and/or CD3CD2O− derivatives of 3. Assignment of the resonances was made based on the 1H-NMR chemical shift data and changes seen in the 1H- and 2H-NMR spectra of the related deuterated complexes. The magnetic susceptibility of complex 3 was measured in the range of 5–300 K. The effective magnetic moment per molecule decreases gradually from 6.44 μB at 300 K to 3.31 μB at 70 K then more dramatically to 0.84 μB at 5 K, indicating a diamagnetic S = 0 ground state consistent with the expected presence of antiferromagnetic exchange interactions between the FeIII ions.