Homo- and heteronuclear iron complexes {Fe2MO} with salicylic acid: Synthesis, structures, and physicochemical properties

A reaction of iron nitrate with magnesium salicylate and reactions of iron and cobalt chlorides with ammonium salicylate in the presence of water, methanol, DMAA, and DMF gave the trinuclear heterometallic complexes: [hexa-μ-salicylato-μ3-oxo-0.4-dimethylacetamide-2.6-aquadiiron(III)magnesium(II)] tetra(dimethylacetamide), [Fe2MgO(SalH)6(DMAA)0.4(H2O)2.6]·4DMAA (I); [hexa-μ]-salicylato-μ3-oxo(dimethanol)aquadiiron(III)cobalt(II)] dimethylformamide · 2.5-hydrate, [Fe2CoO(SalH)6(CH3OH)2(H2O)] · DMF · 2.5H2O (II); and [hexa-μ-salicylato-μ3-oxotriaquatriiron(III)] chloride dimethylacetamide monohydrate, [Fe3O(SalH)6(H2O)3]Cl · DMAA · H2O (III). The X-ray study revealed that the molecular structures of complexes I and II are [Fe2 IIIMII(μ3-O)(RCOO)6L3] · nSolv. The IR and Mossbauer spectra of complexes I–III were examined; their magnetochemical and thermal properties were studied. The parameters of the Mossbauer spectra (δNa + = 0.69 ± 0.03 mm/s, ΔE Q = 0.76–1.08 mm/s, 300 K) suggest the high-spin state of the Fe3+ ions in complexes I–III (S = 5/2). The paramagnetic Fe3+ ions are involved in antiferromagnetic exchange interactions with the parameter J = −44 cm−1, g = 2.05 (for I). Complexes I–III are thermally unstable.