Chelate‐Thiolate‐Coordinate Ligands Modulating the Configuration and Electrochemical Property of Dinitrosyliron Complexes (DNICs)

Abstract

As opposed to the reversible redox reaction ({Fe(NO)2 }(10) reduced-form DNIC [(NO)2 Fe(S(CH2 )3 S)](2-) (1)⇌{Fe(NO)2 }(9) oxidized-form [(NO)2 Fe(S(CH2 )3 S)](-) ), the chemical oxidation of the {Fe(NO)2 }(10) DNIC [(NO)2 Fe(S(CH2 )2 S)](2-) (2) generates the dinuclear {Fe(NO)2 }(9) -{Fe(NO)2 }(9) complex [(NO)2 Fe(μ-SC2 H4 S)2 Fe(NO)2 ](2-) (3) bridged by two terminal [SC2 H4 S](2-) ligands. On the basis of the Fe K-edge pre-edge energy and S K-edge XAS, the oxidation of complex 1 yielding [(NO)2 Fe(S(CH2 )3 S)](-) is predominantly a metal-based oxidation. The smaller S1-Fe1-S2 bond angle of 94.1(1)° observed in complex 1 (S1-Fe1-S2 88.6(1)° in complex 2), compared to the bigger bond angle of 100.9(1)° in the {Fe(NO)2 }(9) DNIC [(NO)2 Fe(S(CH2 )3 S)](-) , may be ascribed to the electron-rich {Fe(NO)2 }(10) DNIC preferring a restricted bite angle to alleviate the electronic donation of the chelating thiolate to the electron-rich {Fe(NO)2 }(10) core. The extended transition state and natural orbitals for chemical valence (ETS-NOCV) analysis on the edt-/pdt-chelated {Fe(NO)2 }(9) and {Fe(NO)2 }(10) DNICs demonstrates how two key bonding interactions, that is, a FeS covalent σ bond and thiolate to the Fe d z 2 charge donation, between the chelating thiolate ligand and the {Fe(NO)2 }(9/10) core could be modulated by the backbone lengths of the chelating thiolate ligands to tune the electrochemical redox potential (E1/2 =-1.64 V for complex 1 and E1/2 =-1.33 V for complex 2) and to dictate structural rearrangement/chemical transformations (S-Fe-S bite angle and monomeric vs. dimeric DNICs).

Theoretical Investigations on the Mechanistic Aspects of O2 Activation by a Biomimetic Dinitrosyl Iron Complex

“…Earlier theoretical investigations have identified two possible oxidation states of DNIC complexes, that is, {Fe(NO) 2 } 9 and {Fe(NO) 2 } 10 . Shengfa et al.…”

A Quantitative Description of the σ‐Donor and π‐Acceptor Properties of Substituted Phenanthrolines

“…Furthermore, when NOCV is associated with an energy decomposition analysis scheme [in particular with the extended transition state (ETS) method, initially developed by Ziegler and Rauk], it is possible to give a quantitative (i.e., energetic) description of the σ‐donor ( E σ ) and π‐acceptor ( E π ) contributions to the metal–ligand bond. Thus, in the last years, the ETS‐NOCV approach has emerged as a very precious tool for shedding light on the nature of metal‐to‐ligand interactions, as documented in the different cases studied . In the present study, we applied ETS‐NOCV to a series of [Mo(CO) 4 (phen*)] complexes (phen* = substituted 1,10‐phenanthroline) with the purpose of describing and quantifying the σ‐donor and π‐acceptor properties of phen* depending on their substitution.…”

Dinitrosyl Iron Complex [K‐18‐crown‐6‐ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide

“…Complex 2-CO 2 displays the same Fe 1s !Fe 3d pre-edge energy as complex 2 at 7113.5 eV, which characterizes its {Fe(NO) 2 } 10 electronic structure (Supporting Information, Figure S8). [12] As shown in Figure 2, IR n CO 2 and n NO absorption peaks at 1723 and (1686, 1636) cm À1 are exhibited by complex 2-CO 2 . When 13 CO 2(g) and 15 NO-labeled complex 2 are used, shift of these IR n CO 2 and n NO absorption peaks to 1699 and (1655, 1603) cm À1 , respectively, demonstrates the capture of CO 2 during the 2-to-2-CO 2 conversion.…”

“…IR spectra of A) 12 CO 2 -/ 13 CO 2 -labeled (blue/red) and B) 14 NO-/ 15 NO-labeled (blue/pink) 2-CO 2 in THF. C) 13 C NMR spectra of 12…”

“…In addition to the Fe 1s !Fe 3d pre-edge energy of 7113.5 eV, sharp 1 H/ 13 C NMR signals and EPR silence exhibited by complex 2 corroborate its diamagnetic {Fe(NO) 2 } 10 -{Fe(NO) 2 } 10 electronic configuration (Supporting Information, Figures S5-S8). [12] Moreover, dominant contribution of Fe 3d z 2 orbital to the LUMO of complex 1 and HOMO of complex 2 demonstrates a metal-based reduction process during the 1to-2 conversion (Supporting Information, Figure S9).…”