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

摘要

The structural, spectroscopic, and magnetochemical characteristics of a new hexanuclear iron-oxo complex are reported. [Fe6O3(O2CMe)(9)(OEt)(2)(bpy)(2)]ClO4.1/4EtOH .1/4H(2)O (3 .1/4EtOH .1/4H(2)O) crystallizes in the triclinic space group P (1) over bar with a=11.524(1) Angstrom, b=15.865(2) Angstrom, c=17.029(2) Angstrom, alpha =65.92(1)degrees, beta =81.49(1)degrees, gamma =76.40(1)degrees, V=2758 Angstrom (3), 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. H-1- and H-2-NMR spectra are reported for two [Fe6O3](12+) complexes, 3 and the 4,4'-Me(2)bpy analog 4, as well as CD3CO2- and/or CD3CD2O- derivatives of 3. Assignment of the resonances was made based on the H-1-NMR chemical shift data and changes seen in the H-1- and H-2-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 mu (B) at 300 K to 3.31 mu (B) at 70 K then more dramatically to 0.84 mu (B) at 5 K, indicating a diamagnetic S=0 ground state consistent with the expected presence of antiferromagnetic exchange interactions between the Fe-III ions. [References: 72]