Tungsten based oxides

In spite of the apparent chemical reversibility of the first anodic step, likely centered on the ferrocenyl fragment, in the long times of macroelectrolysis the monocation [(C5H5)Fe C5H4[C5H3(3,4-Me)2]W(CO)3(Me) ] undergoes slow decomposition. The same happens for the subsequent, tungsten-based, oxidation product [66]. 

Synthesis From Other Ring Systems. These syntheses are further classified based on the number of atoms in the starting ring. Ring expansion of dichlorocyclopropane carbaldimine (53), where R = H and R = ryl, on pyrolysis gives 2-arylpyridines. Thermal rearrangement to substituted pyridines occurs in the presence of tungsten(VI) oxide. In most instances the nonchlorinated product is the primary product obtained (63). 

Figure 11.36 Frequency count for the oxidative conversion of methylcyclohexene of a tungsten-based library.

Le Roux, E. (2004) New Generation of Tantalum and Tungsten Based Catalysts Supported on Oxides for Alkane Metathesis. PhD thesis. University Claude Bemard-Lyon I (Lyon). 

During the past several years it has been shown that both molybdenum and tungsten in oxidation states of +4 or thereabouts, have marked predilection to form trinuclear duster species. For the tungsten cluster spedes, there are three different structural types with respect to the ligand arrangements (Figure 24 a, b, c) which are based on an equilateral triangle of M—M bonded atoms. Structure (a) contains th [W3(j 3-X)(ju-Y)3] nucleus, where X = 0, Cl,... 

Many of the first papers which discussed the use of (selective) CVD of tungsten for IC applications used conventional hot wall tube CVD reactors [Broadbent et al.44, Pauleau et al.45, Cheung47]. This type of reactor was and still is the workhorse in IC fabs. Excellent films such as TEOS based oxides, thermal silicon-nitride and poly-silicon can be grown in such equipment. Hot wall tube reactors are suitable for these films because such materials stick very well to quartz tubes and are quite transparent to IR radiation of the heating elements. Thus neither particle nor temperature control is a problem. One other major advantage is that high throughputs are typically obtained. 

Baeck, S. H. Jaramillo, T. F. Brandli, C. McFarland, E. W., Combinatorial electrochemical synthesis and characterization of tungsten-based mixed-metal oxides, J. Comb. Chem. 2002,... 

The effect of the addition of 0.1 mol of alkali metal to tungsten blue oxide is shown in Table 3.1. It can be seen that the influence in grain growth is considerable. Moreover, there are differences between the different metals which are mainly based on the properties of the metal. At the end of the reduction process the respective alkali tungstate is reduced and at 1000 °C the metal is evaporated. The vapor piessiue of Li is the lowest of the three metals and therefore the amount remaining is the highest. 

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