ChemInform Abstract: Multiple Bonds Between Main-Group Elements and Transition Metals. Part 40. Glycolate and Thioglycolate Complexes of Rhenium and Their Oxidative Elimination of Ethylene and of Glycol.

ChemInform Abstract

The Criegee and the Sharpless variants of olefin oxidation on MnO^4- and OsO₄-catalysts, resp., presumably proceed via glycolate complexes as intermediates. A model for such a system is the readily available complex (Va) (space group P2₁2₁2₁, Z=4), which undergoes several degradation reactions. Thermolysis in the absence of air yields ethylene and (I) quantitatively, whereas in the presence of air (Va) is transformed to the more complex oxidation product (VI), crystallizing in the space group P1 with Z=2. Under acid and/or oxidative conditions (diluted HCl or H₂O₂) glycol is selectively eliminated from (Va) with formation of (III) or (I). The dithio analogue is thermally more stable, but also loses ethylene quantitatively at 200 °C within 30 minutes. The ReO₂C₂ metallacycle stillpresent in (VI) no longer decomposes with elimination of ethylene even at temp. as high as 250 °C.