Sluggish reactivity by a nonheme iron(iv)-tosylimido complex as compared to its oxo analogue

Abstract

High-valent iron-nitrido intermediates have been postulated as reactive intermediates in various enzymes, including the nitrogenases and the cytochromes P450, but so far few have been trapped and characterized. As little is known about their oxidative and spectroscopic properties, we decided to create biomimetic models of iron(IV)-imido complexes and compare their structure and reactivity with analogous iron(IV)-oxo systems. In this work we report the synthesis and spectroscopic characterization of a novel [Fe^IV(NTs)(Bntpen)]²⁺ complex (Bntpen = N¹-benzyl-N¹,N²,N²-tris(pyridine-2-ylmethyl)ethane-1,2-diamine) and study its reactivity patterns with respect to hydrogen atom abstraction and nitrogen atom transfer reactions. The work is compared with analogous pentadentate ligand systems as well as with iron(IV)-oxo species with the same ligand features and highlights the differences in chemical properties and reactivity patterns. It is shown that the reactivity is dependent on the metal ligand system that affects the physicochemical properties of the oxidant such as the redox potential, which is the main driving force for the reaction mechanism with substrates.