摘要
The reversible redox transformations [(NO) <sub>2</sub> Fe(S <sup>t</sup> Bu) <sub>2</sub> ] <sup>-</sup> ⇌ [Fe(μ-S <sup>t</sup> Bu)(NO) <sub>2</sub> ] <sub>2</sub> <sup>2-</sup> ⇌ [Fe(μ-S <sup>t</sup> Bu)(NO) <sub>2</sub> ] <sub>2</sub> <sup>-</sup> ⇌ [Fe(μ-S <sup>t</sup> Bu)(NO) <sub>2</sub> ] <sub>2</sub> and [cation][(NO) <sub>2</sub> Fe(SEt) <sub>2</sub> ] ⇌ [cation] <sub>2</sub> [(NO) <sub>2</sub> Fe(SEt) <sub>2</sub> ] (cation = K <sup>+</sup> -18-crown-6 ether) are demonstrated. The countercation of the {Fe(NO) <sub>2</sub> } <sup>9</sup> dinitrosyliron complexes (DNICs) functions to control the formation of the {Fe(NO) <sub>2</sub> } <sup>10</sup> {Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced Roussins red ester (RRE) [PPN] <sub>2</sub> [Fe(μ-SR)(NO) <sub>2</sub> ] <sub>2</sub> or the {Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced monomeric DNIC [K <sup>+</sup> -18-crown-6 ether] <sub>2</sub> [(NO) <sub>2</sub> Fe(SR) <sub>2</sub> ] upon reduction of the {Fe(NO) <sub>2</sub> } <sup>9</sup> DNICs [cation][(NO) <sub>2</sub> Fe(SR) <sub>2</sub> ] (cation = PPN <sup>+</sup> , K <sup>+</sup> -18- crown-6 ether; R = alkyl). The binding preference of ligands [OPh] <sup>-</sup> /[SR] <sup>-</sup> toward the {Fe(NO) <sub>2</sub> } <sup>10</sup> {Fe(NO) <sub>2</sub> } <sup>10</sup> motif of dianionic reduced RRE follows the ligand-displacement series [SR] <sup>-</sup> > [OPh] <sup>-</sup> . Compared to the Fe K-edge preedge energy falling within the range of 7113.6-7113.8 eV for the dinuclear {Fe(NO) <sub>2</sub> } <sup>9</sup> {Fe(NO) <sub>2</sub> } <sup>9</sup> DNICs and 7113.4-7113.8 eV for the mononuclear {Fe(NO) <sub>2</sub> } <sup>9</sup> DNICs, the {Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced monomeric DNICs and the {Fe(NO) <sub>2</sub> } <sup>10</sup> {Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced RREs containing S/O/N-ligation modes display the characteristic preedge energy 7113.1-7113.3 eV, which may be adopted to probe the formation of the EPR-silent {Fe(NO) <sub>2</sub> } <sup>10</sup> -{Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced RREs and {Fe(NO) <sub>2</sub> } <sup>10</sup> dianionic reduced monomeric DNICs in biology. In addition to the characteristic Fe/S K-edge preedge energy, the IR v <sub>NO</sub> spectra may also be adopted to characterize and discriminate [(NO) <sub>2</sub> Fe(μ-S <sup>t</sup> Bu)] <sub>2</sub> [IR v <sub>NO</sub> 1809 vw, 1778 s, 1753 s cm <sup>-1</sup> (KBr)], [Fe(μ-S <sup>t</sup> Bu)(NO) <sub>2</sub> ] <sub>2</sub> <sup>-</sup> [IR v <sub>NO</sub> 1674 s, 1651 s cm <sup>-1</sup> (KBr)], [Fe(μ-S <sup>t</sup> Bu)(NO) <sub>2</sub> ] <sub>2</sub> <sup>2-</sup> [IR v <sub>NO</sub> 1637 m, 1613 s, 1578 s, 1567 s cm <sup>-1</sup> (KBr)], and [K-18-crown-6 ether] <sub>2</sub> [(NO) <sub>2</sub> Fe(SEt) <sub>2</sub> ] [IR v <sub>NO</sub> 1604 s, 1560 s cm <sup>-1</sup> (KBr)]. © 2012 American Chemical Society.