Rhenium oxygen containing

The same is true of rhenium catalysts rhenium heptoxide [42], rhenium heptasulfide [5i] and rhenimn heptaselenide [54] all require temperatures of 100-300° and pressures of 100-300 atm. Rhenium heptasulfide is not sensitive to sulfur, and is more active than molybdenum and cobalt sulfides in hydrogenating oxygen-containing functions [55,55]. 

The most prevalent complexes of this oxidation state are those which contain the [ReO] ", [Re02] and [RejOj] moieties, a reflection of the increasing stability of the rhenium-oxygen bond as the oxidation state increases. The tendency of Re to form multiple bonds (as in [Re=0] and [0=Re=0] ) is also seen in its behavior toward nitrogen, viz. the stabilization of the [Re=N] (nitrido) and [Re=NR] + (nitrene) moieties. With few exceptions, complexes of Re have been found to be essentially diamagnetic, i.e. to contain a spin-paired configuration. Because of the dominance of the [ReO] +, [Re02] and [RejOj] units in the chemistry of Re, such complexes will be considered first in the chemistry of this oxidation state. 

The molecular geometry of is depicted in Figs. 1, giving proof that we are indeed dealing with a mononuclear species containing short rhenium-oxygen bonds. The ReO interatomic distances of ca. 171 pm are... 

Because several of the superalloys contain very little iron, they are closely related to some of the non-ferrous alloys. Some of the second- and third-row transition metals possess many of the desirable properties of superalloys. They maintain their strength at high temperatures, but they may be somewhat reactive with oxygen under these conditions. These metals are known as refractory metals, and they include niobium, molybdenum, tantalum, tungsten, and rhenium. 

When the decomposition reaction is performed in silica or glass containers, Nb(0,F)3 results. These materials are gray-black to black, refractory materials having the rhenium trioxide type of cubic structure, with a cell constant varying from 3.889 to 3.917 A.2 These materials contain variable amounts of oxygen and have often been erroneously identified as NbF3. 

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