Achieving One-Electron Oxidation of a Mononuclear Nonheme Iron(V)-Imido Complex

Abstract

A mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [FeV(NTs)(TAML)]− (1), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [FeV(NTs)(TAML+•)] (2); 2 is a diamagnetic (S = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (S = 1/2) with the one-electron oxidized ligand (TAML+•). 2 is a competent oxidant in C–H bond functionalization and nitrene transfer reaction, showing that the reactivity of 2 is greater than that of 1.

C–H activation and nucleophilic substitution in a photochemically generated high valent iron complex

“…Notably, although valence tautomerisation is observed in some synthetic porphyrinoid counterparts, 11 , 12 , 14 anion-dependent valence tautomerisation in non-heme iron systems is very uncommon. 40 , 41 The reported radical-cations often show enhanced substrate C–H activation behavior, 47 similar to reports on cytochrome P450, and recently on Mn IV (O-LA)(TBP8Cz˙ + ) (LA = Lewis acid, TBP8Cz = octakis( p-tert -butylphenyl)corrolazinato 3– ) as well. 14 However, we show that radical-cations on sterically unprotected ligands, such as, 1-TAML˙ + , can undergo unprecedented C–H activation followed by nucleophilic halogen substitution on the TAML aryl ring.…”

Uncatalyzed Oxidative C−H Amination of 9,10‐Dihydro‐9‐Heteroanthracenes: A Mechanistic Study

“…[35] Especially xanthenei sacommonly used substrate to investigate reaction kinetics of such reactions. [28][29][30][31]33] In the courseo fo ur investigations,w ei nitially reasoned in a similar manner.H owever,m uch to our surprise, we observed that sulfonamides are able to react with xantheneand thioxanthene in the presence of ab enzoquinoned erivativea sas acrificial oxidant and base, without the need for a( transitionmetal) catalyst. Even more interestingly, we also observed that dihydroheteroanthracenes react with commonly used iminoiodanes to afford the corresponding aminationp roduct in the absence of any catalyst (Figure 1).…”

“…Therefore, dihydroheteroanthracenes are often assumed to be suitable model substrates to test for basic C−H amination activity, even for relatively non‐reactive nitrene intermediates . Especially xanthene is a commonly used substrate to investigate reaction kinetics of such reactions …”

“…[25,26] Our group is interested in the formation and characterization of new metal-nitrene complexes from known nitrenep recursors and ideally directly from primarya mines.A so thers, we adopted the reasoning that successful nitrene transfer could be dictated by the relative bond dissociation free energy (BDFE) of the CÀHb ond, with al ower BDFE expectedly resulting in faster nitrene insertion. [25,[27][28][29][30][31][32][33] Dihydroheteroanthracenes (xanthene,t hioxanthene, and dihydroacridine derivatives) have low CÀHb ond dissociation energies (BDE) in the range of 74-81 kcal mol À1 . [34] Therefore, dihydroheteroanthracenes are often assumedt ob es uitable model substrates to test forb asic CÀH amination activity,even for relativelynon-reactive nitrene intermediates.…”

A Manganese(V)–Oxo Tetraamido Macrocyclic Ligand (TAML) Cation Radical Complex: Synthesis, Characterization, and Reactivity Studies

“…Very recently, we reported an iron(V)–imido TAML cation radical complex, [Fe V (NTs)(TAML +. )], which was synthesized by oxidizing an iron(V)–imido complex, [Fe V (NTs)(TAML)], with one‐electron oxidants, such as [Fe III (bpy) 3 ] 3+ , tris(4‐bromophenyl)‐ammoniumyl hexachloroantimonate {[(4‐BrC 6 H 4 ) 3 N ]SbCl 6 }, and [Ru III (bpy) 3 ] 3+ . Herein, we have demonstrated that the oxidation of [Fe V (NTs)(TAML)] occurs on the TAML ligand, not on the iron ion .…”