Activation of Metal Oxo and Nitrido Complexes by Lewis Acids.

Metal oxo species (M═O) play key roles as oxidants in chemical and biological systems. Although Brønsted acids have long been known to enhance the oxidizing power of metal oxo complexes, the use of Lewis acids (LAs), such as metal ions, to activate these complexes has received much less attention until recently. The report of the presence of a Mn4CaO5 cluster active site in the oxygen-evolving center of photosystem II in 2004 has stimulated intense interest in understanding the interaction of LAs with metal oxo species. This Perspective analyzes the various modes of activation of metal oxos by LAs and the pathways for the oxidation of various substrates by LA/M═O systems. The interaction of LAs with metal nitrides will also be discussed, although it is much less studied than that with metal oxo complexes.