The two compounds, trans-Cp 2 Mo 2 O 2 (μ-O)(μ-Te) and cis-Cp 2 Mo 2 O 2 (μ-O)(μ-S), were isolated in 31% and 36% yields respectively, when a benzene solution of Cp 2 Mo 2 Fe 2 (CO) 7 (μ 3 -S)(μ 3 -Te) was refluxed for 3 h in the presence of air. Characterisation was carried out by IR, 1 H NMR and 1 2 5 Te NMR spectroscopy. The structures, established by single crystal X-ray diffraction analysis, consist of an oxo-bridged dimolybdenum unit containing a μ 2 -Te atom in one case and a μ 2 -S atom in the other. Also attached to each Mo atom are a Cp ligand and a terminally bonded oxo group.