Thermal decomposition of the methoxide complexes MoO(OMe)4, Re4O6(OMe)12 and (Re1−xMox)O6(OMe)12 (0.24≤x≤0.55)

The thermal decomposition of the methoxide complexes MoO(OMe)4 (I), Re4O6(OMe)12 (II) and (Re1−xMox)O6(OMe)12 (0.24≤x≤0.55) (III) in hydrogen and nitrogen at T≤800 °C and in air at temperatures T≤400 °C 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)O2 (with 0.24≤x≤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 σ-phase) at surprisingly low temperatures, around 520, 240 and 360 °C for I, II and III, respectively.