查看文章

Many first-row transition metals are able to transfer oxygen to organic substrates;[','] the epoxidation of olefins is an example of particular relevance in synthesis.[31 The reactive species is usually formulated as a high-valent complex with a terminal metal-oxo multiple bond. Isolation and characterization of such complexes has been successful in only a few cases. Kochi and co-~ orkers [~'demonstrated that cationic Mn"'complexes of the planar tetradentate ligand salen (salen= N, N'-bis (sa1icy1idene) ethylenediamine dianion) are highly efficient catalysts for epoxidation with a variety of terminal oxidants such as