The thermal decomposition of the methoxide complexes MoO(OMe)(4) (I), Re4O6(OMe)(12) (II) and (Re1-xMox)O-6(OMe)(12) (0.24 less than or equal to x less than or equal to 0.55) (III) in hydrogen and nitrogen at T less than or equal to 800degreesC and in air at temperatures T less than or equal to 400degreesC have been monitored by thermal analysis, X-ray powder diffraction and scanning electron microscopy. Heating of I, II and III in air yields orthorhombic MoO3, ReO3 and a mixture of these two phases, respectively. Thermal treatment of I and II in nitrogen, using heating rates of 20 K min(-1) or faster, yields the same products as in air, while applying slower heating rates of I and thermal treatment of III in nitrogen yield the tetragonal modification Of MoO2 and (Re1-xMox)O-2 (with 0.24 less than or equal to x less than or equal to 0.55), respectively. Heat treatment of I, II and III in hydrogen yields fine powders of Mo, Re or a Re-Mo alloy (having the structure of the sigma-phase) at surprisingly low temperatures, around 520, 240 and 360 degreesC for I, II and III, respectively. (C) 2004 Elsevier B.V. All rights reserved.