Tungsten halides synthesis

Tungsten halides, 3, 974, 984, 988 synthesis, 3,974 Tungsten hexaalkoxides physical properties, 2,347 Tungsten oxide ruthenium oxide support... 

N-methylmorpholine (NMM) and the cheaper oxidant H202 rather than stoichiometric amounts of NMO (Scheme 5.11) [55]. In this process, NMM is reoxidized into NMO by H202 together with tungsten catalyst. LDH-PdOsW asymmetrically catalyzed a one-pot synthesis of chiral diols from aryl halides and olefins (Figure 5.10). 

Near quantitative yields are achieved for the molybdenum halides, but substantially lower yields (50%) are obtained in the synthesis of the tungsten clusters, which require higher temperatures and the use of Vycor reaction vessels. A higher yield low-temperature synthesis was devised by McCarley and co-workers for W6C112 using iron as the reducing agent (14). 

Carbides of metals and other elements have been produced by this approach, including carbides of boron, silicon, titanium, zirconium, hafnium, vanadium, niobium, molybdenum, tungsten, tantalnm, and thorium (Funke, Klementiev, Kosukhin, 1969 Sheppard Wilson, 1972 MacKinnon Wickens, 1973 Chase, 1974 Steiger Wilson, 1974 Swaney, 1974 MacKinnon Renben, 1975). The produced caibide particles are very small their diameter is usually about 20-200 mu. Halides are mixed with hydrocarbons, usually in a ratio H2 Me = 2-30. The gas mixture is heated up in plasma to temperatures of 1300-4000 K time of synthesis exceeds 50 ms. As an example, production of submicron boron carbide powder from gaseous boron trichloride and methane occurs in the strongly endothermic process ... 

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