Methyltrioxorhenium stability

The 14e compound MTO readily forms coordination complexes of the type MTO-L and MTO-L2 with anionic and uncharged Lewis bases [96], These yellow adducts are typically five- or six-coordinate complexes, and the Re-L system is highly labile. Apart from their fast hydrolysis in wet solvents, MTO-L adducts are much less thermally stable then MTO itself. The pyridine adduct of MTO, for instance, decomposes even at room temperature. In solution, methyltrioxorhenium displays high stability in acidic aqueous media, although its decomposition is strongly accelerated at increased hydroxide concentrations [97, 98], Thus, under basic aqueous conditions MTO decomposes as shown in Equation (4). 

Selective oxidation of N-1 of adenine derivatives is typically carried out with peracids <1998JOC3213>, but has also been achieved with hydrogen peroxide and catalytic methyltrioxorhenium (Scheme 10) <2000T10031>. The inclusion of pyridazine-2-carboxylic acid as a stabilizer for reactive rhenium peroxides led to increased yields. Caffeine did not react under these conditions. 

Methyltrioxorhenium(VII) (MTO, 8) has been established as a powerful catalyst for a broad variety of organic transformations [33], MTO has also fotmd several applications in catalytic reactions performed in the aqueous phase, due to its pronounced stability to both water and temperature. A more detailed description of the application of MTO in aqueous systems is given in Section 2.4.3.3. When the particular importance of the presence of the Re-C bond in MTO was noted, the question arose of whether it would be possible to synthesize similar transition metal complexes derived from metals cheaper than Re, which would be applicable for the same purposes and would have comparable stabilities (8-10) [34], Furthermore, would the lower homologues of Re parallel the chemistry of MTO and its derivatives, or differ principally as found within group 8 transition metals. Not... 

AU of these compounds can be prepared from methyltrioxorhenium(Vll), abbreviated as MTO. Reduction to rhenium(V) is accomphshed in these procedures with thiols, phosphanes, and sulfanes. ° Suitable stabdizing ligands must be present to intercept the MeRe02 intermediate, which is quite reactive even perchlorate ions are reduced by it. With neither a stabilizing hgand nor an oxidant, a black precipitate is formed from the polymerization of methyldioxo-rhenium(V). ... 

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