Three new oxo-centered trinuclear complexes, one of them a mixed-valence complex [Mn3O (CH3CO2)6(Py)3] (1) and the others, mixed-metal complexes of [FeCr2O (CH3CO2)6(Py)3] Py (2) and [Fe2CoO(CH3CO2)6(Py)3]Py (3) were synthesized by the direct reaction between metal nitrates and acetic acid. These complexes were characterized by elemental analyses(CHN), atomic absorption spectroscopy and spectral (IR, electronic) studies. These are new type of oxo-bridged mixed-metal complexes in which the carboxylate acid. The UV spectra of the complexes exhibited a strong band in the region 265nm which is related to the (π→π*) transitions of the carboxylate ligand. The IR spectra of these compounds showed two strong stretching vibrations bands, indicating a bridging coordination mode of the carboxylic group of the ligand in the complexes. In this work as well for first time aniline was used as axial ligand wich form fine crystalline compounds.