Structure and Properties of [Fe4S4{2,6-bis(acylamino)benzenethiolato-S}4]2- and [Fe2S2{2,6-bis(acylamino)benzenethiolato-S}4]2-: Protection of the Fe−S Bond by Double NH···S Hydrogen Bonds
摘要:
Iron-sulfur clusters containing a singly or doubly NH...S hydrogen-bonded arenethiolate ligand, [Fe4S4(S-2-RCONHC(6)H(4))(4)](2-) (R = CH3, t-Bu, CF3), [Fe4S4{S-2,6-(RCONH)(2)C6H3}(4)](2-), [Fe2S2(S-2-RCONHC(6)H(4))(4)](2-) (R = CH3, t-Bu, CF3), and [Fe2S2{S-2,6-(RCONH)(2)C6H3}(4)](2-), were synthesized as models of bacterial [4Fe-4S] and plant-type [2Fe-2S] fenedoxins. The X-ray structures and IR spectra of (PPh(4))(2)[Fe4S4{S-2,6-(CH3-CONH)(2)C6H3}(4)]. 2CH(3)CN and (NEt(4))(2)[Fe2S2{S-2,6-(t-BuCONH)(2)C6H3}(4)] indicate that the two amide NH groups at the o,o'-positions are directed to the thiolate sulfur atom and form double NH...S hydrogen bonds. The NH...S hydrogen bond contributes to the positive shift of the redox potential of not only (Fe4S4)(+)/(Fe4S4)(2+) but also (Fe4S4)(2+)/(Fe4S4)(3+) in the [4Fe-4S] clusters as well as (Fe2S2)(2+)/(Fe2S2)(3+) in the [2Fe-2S] clusters. The doubly NH...S hydrogen-bonded thiolate ligand effectively prevents the ligand exchange reaction by benzenethiol because the two amide NH groups stabilize the thiolate by protection from dissociation.
Crystal and Solution Structures of Novel Bulky Bis[2,6-bis(acylamino)phenyl] Disulfides. Absence of Covalent NH.cntdot..cntdot..cntdot.S Hydrogen Bond between Amide NH and Neighboring Disulfide in Bis[2,6-bis(pivaloylamino)phenyl] Disulfide
摘要:
Novel bulky bis[2,6-di(acylamino)phenyl] disulfides, e.g. bis[2,6-di(pivaloylamino)phenyl] disulfide and bis[2,6-di(triphenylacetylamino)phenyl] disulfide, having two acylamino groups at the 2,6-positions of the benzene ring were synthesized and the crystal structures determined. The two bulky acylamino groups cover the disulfide group, and the two amide NH groups are directed toward the sulfur atom, but the IR NH bands observed in the solid state indicate the absence of covalent NH-S hydrogen bonds in bis[2, 6-di(pivaloylamino)phenyl] disulfide.
positive shifted Fe(III)/Fe(II) redox couples by the single and double NH.S hydrogen bond, respectively. The shifts are +0.25 for 2a and +0.56 for 6a from the redox potential of [Fe(II)(SPh)(4)](2-), which indicate additivity of the effect of the NH.S hydrogen bond. The formation and the structure of a novel chelating amido(thiolato) complex (PPh(4))(2)[Co(II)S-2,6-(CF(3)CONH)(2)C(6)H(3)}(2)(S-2-CF(3
Effect of the NH---S Hydrogen Bond on the Nature of Hg−S Bonding in Bis[2-(acylamino)benzenethiolato]mercury(II) and Bis[2,6-bis(acylamino)benzenethiolato]mercury(II) Complexes
2-(Acylamino)benzenethiolate complexes of Hg(II) having an intramolecular NH-S hydrogen bond, Hg[2-(pivaloylamino)benzenethiolato](2) and Hg[2,6-bis(pivaloylamino)benzenethiolato](2), were synthesized and the crystal structures were determined. The crystal structure of Hg[2-(pivaloylamino)benzenethiolato](2) . 1/2H(2)O shows the presence of two distinct conformers with different C-S-(Hg)-S-C torsion angles (81.7 and 176.6 degrees). The crystal structure of Hg[2,6-bis(pivaloylamino)benzenethiolato](2) indicates the presence of ordinary Hg-S bonds (2.335(2) and 2.342(2) Angstrom) and a straight linear coordination (S-Hg-S = 174.7(1)degrees) with a weak interaction of one of the amide CO groups toward HE(II). A weak NH-S hydrogen bond in both complexes is detected from the IR spectra in the solid state. The Hg-199 NMR spectra show the high-field shift with a decrease in the S --> Hg(II) ligand-to-metal charge transfer by the NH-S hydrogen bonding. The high-field shift by the double NH-S hydrogen bond is far greater than that by the p-substituent effect of the electron-withdrawing group (OMe, H, NHCOCH3, Cl, NO2) on the benzenethiolate ring.
Cytochrome P-450 Model (Porphinato)(thiolato)iron(III) Complexes with Single and Double NH···S Hydrogen Bonds at the Thiolate Site
Structure and Properties of [Fe<sub>4</sub>S<sub>4</sub>{2,6-bis(acylamino)benzenethiolato-<i>S</i>}<sub>4</sub>]<sup>2</sup><sup>-</sup> and [Fe<sub>2</sub>S<sub>2</sub>{2,6-bis(acylamino)benzenethiolato-<i>S</i>}<sub>4</sub>]<sup>2</sup><sup>-</sup>: Protection of the Fe−S Bond by Double NH···S Hydrogen Bonds
Iron-sulfur clusters containing a singly or doubly NH...S hydrogen-bonded arenethiolate ligand, [Fe4S4(S-2-RCONHC(6)H(4))(4)](2-) (R = CH3, t-Bu, CF3), [Fe4S4S-2,6-(RCONH)(2)C6H3}(4)](2-), [Fe2S2(S-2-RCONHC(6)H(4))(4)](2-) (R = CH3, t-Bu, CF3), and [Fe2S2S-2,6-(RCONH)(2)C6H3}(4)](2-), were synthesized as models of bacterial [4Fe-4S] and plant-type [2Fe-2S] fenedoxins. The X-ray structures and IR spectra of (PPh(4))(2)[Fe4S4S-2,6-(CH3-CONH)(2)C6H3}(4)]. 2CH(3)CN and (NEt(4))(2)[Fe2S2S-2,6-(t-BuCONH)(2)C6H3}(4)] indicate that the two amide NH groups at the o,o'-positions are directed to the thiolate sulfur atom and form double NH...S hydrogen bonds. The NH...S hydrogen bond contributes to the positive shift of the redox potential of not only (Fe4S4)(+)/(Fe4S4)(2+) but also (Fe4S4)(2+)/(Fe4S4)(3+) in the [4Fe-4S] clusters as well as (Fe2S2)(2+)/(Fe2S2)(3+) in the [2Fe-2S] clusters. The doubly NH...S hydrogen-bonded thiolate ligand effectively prevents the ligand exchange reaction by benzenethiol because the two amide NH groups stabilize the thiolate by protection from dissociation.