A new unsymmetrical oxo-bridged complex [Fe 2 O(OAsPh 3 ) 4 Cl 3 ][FeCl 4 ] CH 3 CN was synthesized and characterized by X-ray structural analysis, elemental analysis, spectral and magnetic data. The compound crystallizes in a monoclinic system, space group P2 1 /c, with a = 13.77(1), b = 21.50(2), c = 25.62(2) 9, β = 90.22(7)°, and Z = 4 (R = 0.0335 for 5859 independent reflections with I > 3σ(I)). Crystal structure analysis revealed that one iron atom is pentacoordinated by four triphenylarsine oxide ligands and a μ-oxo ligand which connects a tetracoordinated iron atom with the chromophore FeCl 3 O. The magnetic properties of the complex were investigated in the 4.2-300 K temperature range and these data correspond to the electron paramagnetic resonance spectra.