Alkylrhenium oxides as homogeneous epoxidation catalysts: activity, selectivity, stability, deactivation

Article abstract of DOI:10.1016/0304-5102(93)E0162-A

Methyltrioxorhenium (VII) (MTO, 1a) and several congeners 1b and 2a-d of formula R-ReO₃ and R-ReO₃·L, respectively, qualify as olefin epoxidation catalysts of high activity and selectivity. Related alkylrhenium (VI) complexes form efficient catalyst precursors as well, since they get oxidized by H₂O₂ to the same active species CH₃ReO(O₂)₂·H₂O (3). The present paper presents a comparison of this novel class of catalysts with the performance of known, commonly used catalysts. Catalyst stability has been recorded and deactivation reactions are described. The synthesis and crystal structure (X-ray diffraction) of the (pale pink-coloured) monomeric amino-functionalized complex O₃Re-CH₂CH₂CH₂N (C₂H₅)₂ (4A) and its (violet) polymeric form (4B) are reported. Only the latter is an active epoxidation catalyst with H₂O₂. An improved laboratory method of the standard catalyst MTO 1a is described.