Polynuclear iron carboxylates present special interest due to their intramolecular magnetic exchange interactions and their application as the simple models of oligonuclear active sites in metalloproteins. By the reaction of iron nitrate nonahydrate with magnesium salicylate monohydrate in methanol at constant stirring the red powder was obtained. By recrystallization of this product from the mixture of dimethylacetamide (DMAA) and tetrahydrofuran the cherry-red monocrystals were obtained. Single-crystal X-ray study has demonstrated that the title complex (1) takes part from the well known group of μ3oxo heteronuclear carboxylates. Crystal 1 is monoclinic and crystallizes in C2/c space group with the following unit cell parameters: a = 43.386(2), b = 15.3037(5), c = 20.8776(6) Å, γ = 103.99(3)°, R = 0.071. It has a molecular structure composed from trinuclear neutral entities [Fe2MgO(C6H4(OH)COO)6(DMAA)0.4(H2O)2.6] and DMAA as solvate molecules in 1:4 ratio. The apical coordination site of the Mg atom are shared between H2O and DMAA molecules with the 0.6 and 0.4 occupancy factors, respectively. The absorption bands in IR spectrum have been attributed as follows: ν(CH)(C6H4) = 3065, νas(CH3) = 2927, νs(CH3) = 2875 cm-1. In the 16001640 cm-1 region two bands are presented, which were assigned to ν(C=O)(DMAA) and ν(C=O)(COO-). The second symmetric vibration of COO group is found in the region 1400-1420 cm-1 and corresponds to νs(COO). The coordinated water molecule is characterised by the vibrations νas(OH)= 3340, νs(OH)= 3212 cm-1. The TG, Mössbauer spectra and magnetic properties are discussed.figureFig. 1. View of the asymmetrical part of the unit cell