Heterometallic alkoxide complexes of variable composition - A new way to ultrafine powders of metal alloys

The anodic oxidation of Re metal in MeOH (Me = CH3) provides a mixture of Re2O3(OMe)(6) and Re(V) oxoalkoxides that on storage or on heating give insoluble and air stable Re4O6-y(OMe)(12+y)(I). I can be also obtained by reaction of Re2O7 with MeOH. In the presence of MoO(OMe)(4), a heterometallic complex ReMoO2(OMe)(7)(II) is formed as intermediate, the final product being Re4-xMoxO6-y(OMe)(12+y)(III). The electrosynthesis in the presence of WO(OMe)(4) gives Re4-xWxO6-y(OMe)(12+y)(IV) only at very high Re : W ratios in solutions and the W content varies in one and the same sample. The dissolution of Re2O7 in the solutions of MO(OMe)(4), M = Mo,W in toluen on reflux yields Re4-xMxO6-y(OMe)(12+y) with uniform Re : M distribution. The cocrystallization of MoO(OMe)(4) and WO(OMe)(4) yields (Mo,W)O(OMe)(4) (V) with almost uniform Mo : W distribution. The thermal decomposition of II and III in inert atmosphere gives fine powder of the (Re,Mo)O-2 phase. The reduction with hydrogen gas converts II and III into an ultrafine powder of Re-Mo alloy at temperatures below 400 degreesC. The latter can be sintered into compact metal at 800-900 degreesC.