Octahedral iron(iv)-tosylimido complexes exhibiting single electron-oxidation reactivity.

High valent iron species are very reactive molecules involved in oxidation reactions of relevance to biology and chemical synthesis. Herein we describe iron(iv)-tosylimido complexes [Fe(NTs)(MePytacn)](OTf) () and [Fe(NTs)(Me(CHPy)tacn)](OTf) (), (MePytacn = -methyl-,-bis(2-picolyl)-1,4,7-triazacyclononane, and Me(CHPy)tacn = 1-(di(2-pyridyl)methyl)-4,7-dimethyl-1,4,7-triazacyclononane, Ts = Tosyl). and are rare examples of octahedral iron(iv)-imido complexes and are isoelectronic analogues of the recently described iron(iv)-oxo complexes [Fe(O)(L)] (L = MePytacn and Me(CHPy)tacn, respectively).

A two-state reactivity model explains unusual kinetic isotope effect patterns in C-H bond cleavage by nonheme oxoiron(IV) complexes.

It's in the bond: The cleavage of C-H bonds by two related oxoiron(IV) complexes shows a range of kinetic isotope effect (KIE) values that exhibit an unusual dependence on the C-H bond strength. Large nonclassical KIEs are observed for bond strengths below 93 kcal mol(-1), while semiclassical values are found above this value (see graph, DHA = 9,10-dihydroanthracene). This nonintuitive behavior can be rationalized by invoking a two-state reactivity model.

A combined NRVS and DFT study of Fe(IV)=O model complexes: a diagnostic method for the elucidation of non-heme iron enzyme intermediates.

Fe=O biomimetic model complexes have been characterized using nuclear vibrational resonance spectroscopy (NRVS). Features and systematic trends in the low energy region reflect equatorial and axial bonding differences that relate to differences in reactivity. These trends have been computationally extended to predict the spectra of putative Fe=O intermediates in non-heme iron enzymes and show the utility of the NRVS method for structural insight.

Spectroscopic and quantum chemical studies on low-spin FeIV=O complexes: Fe-O bonding and its contributions to reactivity.

High-valent FeIV=O species are key intermediates in the catalytic cycles of many mononuclear non-heme iron enzymes and have been structurally defined in model systems. Variable-temperature magnetic circular dichroism (VT-MCD) spectroscopy has been used to evaluate the electronic structures and in particular the Fe-O bonds of three FeIV=O (S = 1) model complexes, [FeIV(O)(TMC)(NCMe)]2+, [FeIV(O)(TMC)(OC(O)CF3)]+, and [FeIV(O)(N4Py)]2+. These complexes are characterized by their strong and covalent Fe-O pi-bonds.

Structural insights into nonheme alkylperoxoiron(III) and oxoiron(IV) intermediates by X-ray absorption spectroscopy.

Transient mononuclear low-spin alkylperoxoiron(III) and oxoiron(IV) complexes that are relevant to the activation of dioxygen by nonheme iron enzymes have been generated from synthetic iron(II) complexes of neutral tetradentate (TPA) and pentadentate (N4Py, Bn-TPEN) ligands and structurally characterized by means of Fe K-edge X-ray absorption spectroscopy (XAS). Notable features obtained from fits of the EXAFS region are Fe-O bond lengths of 1.78 A for the alkylperoxoiron(III) intermediates and 1.

Nonheme FeIVO complexes that can oxidize the C-H bonds of cyclohexane at room temperature.

Nonheme oxoiron(IV) complexes of two pentadentate ligands, N4Py (N,N-bis(2-pyridylmethyl)-bis(2-pyridyl)methylamine) and Bn-tpen (N-benzyl-N,N',N'-tris(2-pyridylmethyl)-1,2-diaminoethane), have been generated and found to have spectroscopic properties similar to the closely related tetradentate TPA (tris(2-pyridylmethyl)amine) complex reported earlier. However, unlike the TPA complex, the pentadentate complexes have a considerable lifetime at room temperature. This greater thermal stability has allowed the hydroxylation of alkanes with C-H bonds as strong as 99.