Trimethylstannyl perrhenate

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]. 

MTO is generated by methylation of oxidic Re " precursor compounds under nonreducing conditions. Thus, dimethylzinc and methyl Grignard compounds are not very well suited for this purpose. The first commonly applied synthesis started from dirhenium heptoxide using the toxic tetramethyltin as methylating reagent (eq. (1)). The major drawback in this otherwise excellent approach is the loss of half of the Re due to formation of the low-reactivity trimethylstannyl perrhenate [2]. 

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