The synthesis and characterization of oxo-, hydroxo- and alkoxo-bridged 3d-metal compounds attract huge interest owing to their architectural beauty and possibilities to exhibit interesting magnetic properties such as single molecule magnets (SMMs). Furthermore, polynuclear iron(III) clusters can be used as building blocks for the construction of cluster-based coordination polymers [1] . A new hexanuclear iron(III) compound [Fe6O(thme)4Cl6](mdeaH3)2∙(MeCN) (1) has been prepared by the reaction of μ3-oxo trinuclear iron(III) isobutyrate precursor with 1,1,1-tris(hydroxymethyl)-ethane (thmeH3) and methyldiethanolamine (mdeaH2) ligands under hydrothermal conditions. A single-crystal X-ray diffraction analysis showed that 1 crystalizes in the tetragonal space group I-42d and consists of an anionic [Fe6O(thme)4Cl6]2 cluster, two outersphere protonated mdeaH3+ and acetonitrile molecule. In the anionic cluster with C2 molecular symmetry a central oxygen atom resides on two fold axis and is surrounded by six Fe(III) centers to form an octahedron (Fig. 1). Twelve alkoxo groups of four triply deprotonated thme ligands additionally bridge the Fe(III) atoms. All six Fe(III) atom in 1 are six-coordinated and adopt an elongated octahedral O5Cl environment by one Cl atom and five O atoms: one central μ6-O atom and four O atoms from two neighboring thme3 ligands. The long bond distances from each Fe(III) atoms to the central μ6-O atom vary from 2.223 to 2.265 Å, and other FeO bonds are in the range 1.980 - 1.995 Å. Thermogravimetric analysis showed that compound 1 is thermally stable up to 140°C and then step by step completely decomposes reaching temperature 700°C with the formation of iron oxides. The spectroscopic and magnetic measurements have been also studied and all data will be discussed.figureFig. 1. Structure of hexanuclear iron(III) [Fe6O(thme)4Cl6]2- cluster (left) and a view of {Fe6O13}8+ core (right).