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

Chemistry (Weinheim an der Bergstrasse, Germany) (2015-09-26)
Shih-Wey Yeh, Chih-Wei Lin, Bai-Heng Liu, Chih-Chin Tsou, Ming-Li Tsai, Wen-Feng Liaw
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).

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