Activation of Metal Oxo and Nitrido Complexes by Lewis Acids

Abstract

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 Mn 4 CaO 5 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.

A High‐Valent Manganese(IV)–Oxo–Cerium(IV) Complex and Its Enhanced Oxidizing Reactivity

“…[3][4][5][6] Since the redoxinactive Ca 2+ ion in the Mn 4 CaO 5 cluster is an important cofactor in the OÀOb ond formation step in the dioxygenevolving reaction, the role of the redox-inactive metal ions, such as Ca 2+ and Sc 3+ ,h as been investigated extensively in modulating the reactivity of high-valent metal-oxo complexes,such as the increase in the oxidizing capability and the change of mechanism(s), in biomimetic studies. [7][8][9][10][11] However, in contrast to the case of redox-inactive metal ions,h igh-valent metal-oxo complexes binding redox-active metal ions have been rarely synthesized, [12] and the effect of the redoxactive metal ions on the chemical and physical properties of metal-oxo complexes has never been investigated previously.…”

A Systems Approach to a One‐Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode

“…To increase the TPP regeneration from 1 , Sc(OTf) 3 was employed as a redox‐innocent Lewis acid and MeO − acceptor to accelerate the rate‐determining P‐O dissociation step. Sc(OTf) 3 has already been used in other LA‐mediated organic transformations and for the stabilization of high‐valent oxo‐transition‐metal intermediates . In fact, addition of a substoichiometric amount of Sc(OTf) 3 to solutions of 1 and subsequent electrolysis under identical conditions (entry 2 in Table , in presence of MeOTf and PhCHO) resulted in a drastic increase in styrene formation to 63 % yields (Figures S21 and S22).…”

Cooperative activating effects of metal ion and Brønsted acid on a metal oxo species

“…However, in recent years, the use of Lewis acids (LA) such as metal ions and boranes to activate M=O has received tremendous attention (M=O + LA → M=O-LA). [1][2][3] In particular, the interest in understanding the interaction of Lewis acids with metal oxos is stimulated by the discovery that the oxygenevolving center (OEC) of photosystem II (PSII) is composed of a CaMn 3 O 4 cubane and a dangling Mn linked via two µ-oxos. [4][5][6][7][8][9][10] A possible role of Ca 2+ is to function as a Lewis acid to modulate the redox reactivity of the manganese oxo complexes.…”