Chemistry of Methyltrioxorhenium MTO

The title compound has been known for less then 25 years [1]. For a considerable part of this time, it has been widely regarded as a mere curiosity. This picture changed dramatically during the last decade. Today, not only is an amazing wealth of derivatives and reaction products known and easily accessible, several of these compounds, most notably methyltrioxorhenium(VII) itself, have found numerous very interesting applications in both catalysis and material sciences. 

Methyltrioxorhenium(VII) (1), usually abbreviated to MTO, was first reported in 1979 by Beattie and Jones [2]. Due to the difficult synthesis and the low yields of 1 that could be obtained, the compound was not examined further. The break- 

This preparation of 1 has been improved considerably since then [2]. Since 1993, MTO has been commercially available (cf. Section 3.3.13.1.3). In 1997, the synthetic method starting from trimethylstannyl perrhenate has been extended to other perrhenates so that the moisture-sensitive Re207 can be replaced by more conveniently handled starting materials [2]. Nowadays 1 can be synthesized directly from rhenium powder in amounts of several kilograms. This synthetic progress was accompanied by the discovery of a plethora of derivatives and catalytic applications of organorhenium(VII) oxides. The use of these complexes in catalysis, however, is still strongly dominated by 1 itself [2, 3]. 

At room temperature 1 is a colorless solid, crystallizing in colorless needles. It is readily sublimed and soluble in all common solvents. MTO decomposes only above 300 °C. Heated in water to ca. 70 °C for several hours it forms a golden polymer of empirical formula Ho.5[(CH3)o,92Re03]) [4]. 

The catalytic activity of 1 and some of its derivatives is known [5]. However, the breakthrough in the understanding of the role of MTO in oxidation catalysis was the isolation and characterisation of the reaction product of MTO with excess H2O2 it is a bis(peroxo) complex of stoichiometry (CH3)Re(02)20 (2) [6 a]. 

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