Preparation and investigation of highnuclear transition metal coordination clusters attract intense interest due to their interesting magnetic properties and possible application. The treatment of μ3-oxo trinuclear isobutyrate cluster with sodium azide and methyldiethanolamine (H2mdea) under ultrasonic irradiation leads to the formation of a new disk-like octanuclear isobutyrate cluster [Fe8O3(is)6(mdea)3(N3)3(MeO)3] (1) (His = isobutyric acid). A single-crystal X-ray diffraction analysis showed that 1 (Fig. 1) comprises two central axial Fe(III) ions bridged by three μ4-O2–, and each μ4-O2– furthermore bridges two peripheral Fe(III) ions in pair, resulting in one of the three “blades” of the propeller. The central pair of iron ions represents the axle of the propeller with Fe–Fe distances of 2.79 Å. Additionally, Fe(III) ions are bridged by six isobutyrate groups, three mdea2− ligands and three MeO− groups. Three monodentate azide ligands are completed the structure of 1. Thermal studies of 1 showed that cluster is stable up to 185°C, then step by step completely decomposes reaching 400°C. The IR spectrum displays strong bands of the coordinated asymmetric and symmetric carboxylate groups at 1577 cm–1 and 1428 cm–1, respectively. The C−H asymmetric and symmetric stretching vibrations are observed in the range of 2967–2870 cm–1. A very strong peak at 2068 cm−1 corresponds to the N≡N stretching vibrations of azide ligands. Fig. 1. Structure of (1).