O₂ Activation by Bis(imino)pyridine Iron(II)−Thiolate Complexes

Abstract

The new iron(II)-thiolate complexes [(iPrBIP)FeII(SPh)(Cl)] (1) and [(iPrBIP)FeII(SPh)(OTf)] (2) (BIP = bis(iminopyridine)) were prepared as models for cysteine dioxygenase (CDO), which converts Cys to Cys-SO2H at a (His)3FeII center. Reaction of 1 and 2 with O2 leads to Fe-oxygenation and S-oxygenation, respectively. For 1 + O2, the spectroscopic and reactivity data, including 18O isotope studies, are consistent with an assignment of an iron(IV)-oxo complex as the product of oxygenation ([(iPrBIP)FeIV(O)(Cl)] (3)). In contrast, 2 + O2 results in direct S-oxygenation to give a sulfonato product (PhSO3−). The positioning of the thiolate ligand in 1 versus 2 appears to play a critical role in determining the outcome of O2 activation. The thiolate ligands in 1 and 2 are essential for O2 reactivity, and exhibit an important influence over the FeIII/FeII redox potential.

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

“…[166] Substitution of triflate counter anion with different pyridines impacted the reactivity only modestly. [165] Later,i n2 011, [167] the authors demonstrated that the oxidation does not require the thiolate to be covalently anchored on the ligand. Intermediate I was characterizedb ym ass spectrometry/isotopic substitution analysis.T his species was able to readily transfer its O-atomt oP h 3 Pg enerating Ph 3 PO,a nd to exchange the oxygen with water.…”

A Trispyrazolylborato Iron Cysteinato Complex as a Functional Model for the Cysteine Dioxygenase

“…[6] Beyond that, model studies with cyclam iron thiolate complexes and peracids as the oxidant are noteworthy: they showed, again in 2010, that an iron(IV) oxo intermediate [4h] is plausible in the catalytic mechanism of the CDO. [7] Herein we present the successful coordination and dioxygenation of a protected cysteinato ligand to a (His) 3 Fe II analogue and thus the most realistic biomimetic model system to date for the CDO.…”

Protonolysis of Fe–C bonds of a diiminopyridineiron(II) dialkyl complex by acids of different strengths: Influence of monoanionic ligands on the spectroscopic properties of diiminopyiridine-FeY2 complexes

“…[13] The geometry of the iron centre in 5 is approximately octahedral, with the aqua ligand and one of the triflate ligands occupying "axial" positions, i. e., perpendicular to the main coordination plane defined by the three N atoms of the BIP ligand and the second triflate group. This configuration contrasts with that preferred by the analogous manganese complex [Mn(OTf) 2 (OH 2 )( Me2 BIP)], which shows both triflate groups in the axis and the aqua ligand sharing the equatorial plane with the BIP ligand.…”