A study of the reactivity of reduced molybdenum ethoxides: Synthesis and characterization of MoO(OH) and some novel molybdenum ethoxide cluster molecules

摘要

A low temperature route was used in an attempt to produce reduced molybdenum oxides. When molybdenum (III) ethoxide was hydrolyzed with the stoichiometric amount of water in hydrocarbon solvent, a quantitative yield of product was recovered. Elemental and molybdenum oxidation state analyses on this material indicated an empirical formula of Mo[subscript]2(OH)[subscript]5(OEt). When this material was heated in the presence of hydrogen at 250°C, a black solid was produced. Analyses indicated the material is MoO(OH). All attempts to thermally decompose MoO(OH) to the oxide, Mo[subscript]2O[subscript]3, were unsuccessful. A mixture of Mo[subscript]2O[subscript]3 and MoO[subscript]2 was produced instead. However, MoO(OH) was used, successfully, to synthesize LiMoO[subscript]2 from a reaction with Li[subscript]2CO[subscript]3 at 600°C. In addition, MoO(OH) was also used to synthesize Na[subscript] xMoO[subscript]2 (where x = 0.66);In an attempt to remove the final ethoxide ligand of Mo[subscript]2(OH)[subscript]5(OEt) by reaction with water to produce the pure hydroxide species, Mo(OH)[subscript]3, the hydrolysis reaction was completed using an excess (2-4 molar excess) of water. The solid recovered from this reaction still retained the ethoxide ligand and was slightly oxidized by the excess water. Surprisingly, however, the filtrate of the reaction afforded crystals with the formula, Mo[subscript]6O(OEt)[subscript]18 · 4.8H[subscript]2O. The yield of Mo[subscript]6O(OEt)[subscript]18 was very small. Therefore, attempts were made to synthesize it from reactions of Mo(OEt)[subscript]3 with other oxidizing agents, such as Sb[subscript]2O[subscript]5, C[subscript]6H[subscript]5IO, (CH[subscript]3)[subscript]3NO, and N[subscript]2O. However, these reactions did not successfully produce the cluster;Finally, an alternate synthetic route to isolate reduced molybdenum ethoxides was explored. Mo[subscript]2Cl[subscript]4py[subscript]4 was used in a reaction with sodium ethoxide in neat ethanol. When the reaction was carried out at room temperature overnight, a brown crystalline material was isolated from the ethanol. Elemental analysis of this material suggested the empirical formula could be written as Mo[subscript]4(OEt)[subscript]10py. Single crystal x-ray analysis was not completed due to the highly twinned nature of these crystals;When this reaction was completed in refluxing ethanol, a mixture of homoleptic molybdenum ethoxide species was isolated. Furthermore, a reaction of this molybdenum ethoxide mixture with iodosobenzene produced the novel cluster, Mo[subscript]4(OEt)[subscript]14(HOEt)[subscript]2.