The catalytic activity in the hydrodesulfurization (HDS) of thiophene at 370 degreesC was investigated on ex complex catalysts made from the ammonium and sodium, cobalt, and nickel salts of the [Mo3S13](2-) cluster anion supported on gamma -Al2O3 or SiO2 and compared with that of a classic NiMo/Al2O3 catalyst. Samples were characterized by infrared CTR), Raman, UV/VIS, and thermogravimetric measurements. The samples were activated in He at 110 or 400 degreesC, and H2S/H-2 (10% of H2S in H-2) was introduced at room temperature, 110 or 400 degreesC. Furthermore, the NiMo/Al2O3 catalyst was activated directly from room temperature to 400 degreesC in H2S/H-2. The initial sulfidation temperature (400 degreesC or room temperature) did not influence the activity of the ex complex catalysts, whereas the classic NiMo/Al2O3 catalyst was very sensitive to the initial temperature of the sulfidation. The sample treated at 400 degreesC and sulfided starting at room temperature exhibited a much higher activity than the sample to which H2S/H-2 was added at 400 degreesC. Thermal treatment of the catalyst in He at 110 degreesC as opposed to 400 degreesC led to a lower activity of the ex complex catalysts and to a higher activity of the NiMo/Al2O3 catalyst. Catalyst samples made from Na-2[Mo3S13]. 5H(2)O/Al2O3 were slightly less active than the samples obtained from (NH4)(2)[Mo3S13].H2O/Al2O3.