Issue 18, 2019

Insight into chalcogenolate-bound {Fe(NO)2}9 dinitrosyl iron complexes (DNICs): covalent character versus ionic character

Abstract

The synthesis, characterization and transformation of the thermally unstable {Fe(NO)2}9 dinitrosyl iron complex (DNIC) [(OMe)2Fe(NO)2] (2) were investigated. The {Fe(NO)2}9 DNIC 2 characterized by single-crystal X-ray diffraction is exclusively stabilized by the weak intermolecular [Fe(OMe)2⋯(K+)] interactions (O(3)⋯K(1) and O(4)⋯K(1) distances of 2.818(3) and 2.810(3) Å, respectively). The binding affinity of chalcogenolate-containing ligands toward the {Fe(NO)2}9 motif follows the series [SEt] > [SPh] > [OPh] > [OMe], which is dictated by the synergistic cooperation of the electron-donating order ([SEt] > [SPh] > [OPh]) and the soft–hard order (from soft to hard, [SEt] ∼ [SPh] > [OPh] > [OMe]). In comparison with the XAS Fe K-edge pre-edge energy of {Fe(NO)2}9 [(RS)2Fe(NO)2] (R = Ph (4), Et (5)) and [(PhO)2Fe(NO)2] (6) DNICs falling within the reported range of 7113.4–7113.9 eV, the distinctive pre-edge energy of 7114.2 eV exhibited by complex 2 suggests that the electronic structure of {Fe(NO)2}9 DNIC 2 may be qualitatively described as a {FeIII(NO)2}9 electronic structure induced by the dominant ionic character of Fe–OMe bonds, instead of the resonance hybrids of {FeII(NO)(˙NO)}9 and {FeIII(NO)2}9 electronic structures induced by the dominant metal–ligand covalency of {Fe(NO)2}9 DNICs 4–6. As shown in TD-DFT computation, the increased population of NO ligands in MO 125β (45.1% NO) attenuating the OMe-induced polarization imposed on the Fe center through the delocalized covalent nature of Fe–NO bonds supports the lower/synergistic NO/OMe → Fe charge transfer energy (1216 nm) observed in the solid-state UV-vis spectrum of complex 2 compared to those (1140 nm) of complexes 4–6.

Graphical abstract: Insight into chalcogenolate-bound {Fe(NO)2}9 dinitrosyl iron complexes (DNICs): covalent character versus ionic character

Supplementary files

Article information

Article type
Paper
Submitted
18 ربيع الأول 1440
Accepted
19 جمادى الأولى 1440
First published
22 جمادى الأولى 1440

Dalton Trans., 2019,48, 6040-6050

Insight into chalcogenolate-bound {Fe(NO)2}9 dinitrosyl iron complexes (DNICs): covalent character versus ionic character

P. Liu, F. Tsai, B. Chen, I. Hsu, H. Hsieh and W. Liaw, Dalton Trans., 2019, 48, 6040 DOI: 10.1039/C8DT04670K

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