Reactions of Metal Complexes with Singlet Oxygen

Abstract

Abstract A variety of reactions of metal complexes with singlet oxygen have been reported during the past several decades. These reactions can be divided into two parts, that is, reactions of the metal center and ligand oxidations. Reactions at the metal center involve physical deactivation of singlet oxygen and oxidative addition to form metal‐dioxygen complexes. These peroxo complexes may undergo insertion reactions or lose the added dioxygen molecule either in the singlet or triplet state. Reaction of some metal centers with hydrogen peroxide may also lead to formation of singlet oxygen which constitutes a dark (non‐photochemical) method of 1 O 2 generation. Olefinic ligands bound to Sn, Si, and W centers undergo singlet oxygen ene reactions, leading to conventional H‐ene products and/or peroxides bound to the metal atom (metallo‐ene reaction). These peroxides may be useful synthons for further transformations. Examples of [2+2] and [4+2] cycloaddition of singlet oxygen to ligands are also discussed. Finally, singlet oxygen reacts with metal‐bound thiolates and dithiolates, leading to formation of a variety of oxidized sulfur ligands, such as sulfenates and sulfinates. The mechanisms of these reactions appear to be somewhat similar to that of the photooxidation of organic sulfides but many details are poorly understood at this time.