Rhenium systems

In the niobium system the t) -H2 form is marginally the more stable, with AH = 2.0kJmol, whereas in the rhenium system, it is the tetrahydrido form which is the more stable, with — AG208 = 2.5 kJmol and — AH -- 4.6kJmol. ... 

We have attempted to find conditions which will allow us to watch the species build up, to isolate it kinetically, and to observe its reactions directly. That does not imply that the intermediate is unreactive. The remarkable feature of the intermediate in your rhenium system is the apparently facile oxygen atom transfer. 

The attraction of the rhenium system is that deprotection of the pyrrole can readily be achieved by treatment with acid and DMSO, which replaces the kinetically labile i7- -pyrrole ligand on the metal [87JOM(326)C17 90H(31)383]. However, the relatively high cost of rhenium will almost certainly preclude its synthetic use as a pyrrole protecting group, especially when compared with the alternative methods discussed above. 

Silyl manganese pentacarbonyl decomposes in a more complex way to give a mixture of two phases, "MnSi (actually a silicon-rich nonstoichiometric phase of approximate composition MnSii.25) and stoichiometric Mn5Si3, such that the overall metal silicon ratio is 1 1. The analogous rhenium system behaves similarly. 

The discoverythat bulk mutual solubility is not an essential pre-requisite for the formation of a stable surface bimetallic phase opened the way for extensive research, particularly on the ruthenium-copper system. The platinum-rhenium system has also proved of interest because of its use in petroleum reforming, but the platinum-iridium system, which is of comparable importance, has not been so widely examined with the smaller alkanes. It is convenient to classify the material to be considered in the following way. 

The palladium-rhenium system has been little studied,and rhenium s influence on other metals hardly at all. It rapidly negated the isomerisation activity of palladium, and the reaction of neopentane with hydrogen had a maximum rate (mainly hydrogenolysis) at 50% rhenium. ... 

By analogy with the previous electrochemical studies carried out with [Ru(bpy)2(CO)(Cl)], the dielectronic reduction of CO2 to CO (eq. 1), catalysed by the rhenium system, involves the doubly-reduced [Re(bpy)(CO)3l anion [19, 20, 72]. A schematic representation of the overall process is shown in Figure 9. 

These dehydrogenation reactions are essentially hydrogen transfer reactions between the alkane and dimethylbutene. In the case of the rhenium system, the species 17, L2ReH3, was invoked to account for the products of the reactions of 14 with various organic substrates [38]. ITie same species L2ReH3 can also be responsible for the activation of... 

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