Role of oxidation state, ferryl-oxygen, and ligand architecture on the reactivity of popular high-valent FeIV =O species: A theoretical perspective

High-valent iron-oxo species are ubiquitous in nature and are present at the active site of several metalloenzymes which perform challenging organic transformations. Mimicking these metalloenzyme reactivities is one of the growing areas of research, and over the last two decades, tremendous progress has been made to mimic both the structure and function of various heme and non-heme metalloenzymes. Understanding the mechanism of catalytic reactions of these enzymes and their biomimetic models are extremely important to improvise the models further. However, due to the open-shell nature of the catalyst with often close-lying spin-states, the mechanistic aspects associated are highly complex. In this regard, computational tools have played a pivotal role in underpinning the mechanism and several important concepts such as two-state/multi-state reactivity, exchange-enhanced reactivity has emerged. While there are several reviews written already on the reactivity of the popular high-valent Fe-IV=O species, the comparative oxidative ability of this species to other oxidants has not been reviewed. Our group has been working actively in this area, and here we have compared the oxidative ability of the Fe-IV=O to other species with variation arising due to (i) oxidation state (ii) ligand architecture (iii) substitution of oxo by the isoelectronic nitrene species. In this review, theoretical studies undertaken in this spirit are summarised to provide birds-eye-view on the reactivity of the popular Fe-IV=O species. The facts/concepts discussed here will undoubtedly be helpful to design efficient bioinspired catalysts in the years to come. (C) 2020 Elsevier B.V. All rights reserved.