| Sumario: | Transformation of dinitrosyl iron complexes (DNICs) [(NO)[sub2]Fe(SR)[sub2]] (R = Et, Ph) into [4Fe-4S] clusters [Fe[sub4]S[sub4](SPh)[sub4]][sup2-] in the presence of [Fe(SPh)[sub4]][sup2-/1-] and S-donor species S[sub8] via the reassembling process ([(NO)[sub2]Fe(SR)[sub2]][sup-] → [Fe[sub4]S[sub3](NO)[sub7]][sup-] (1)/[Fe[sub4]S[sub3](NO)[sub7]][sup2-] (2) → [Fe[sub4]S[sub4](NO)[sub4]][sup2-] (3) → [Fe[sub4]S[sub4](SPh)[sub4]][sup2-] (5)) was demonstrated. Reaction of [(NO)[sub2]Fe(SR)[sub2]] (R = Et, Ph) with S[sub8] in THF, followed by the addition of HBF[sub4] into the mixture solution, yielded complex [Fe[sub4]S[sub3](NO)[sub7]] (1). Complex [Fe[sub4]S[sub3](NO)[sub7]][sup2-] (2), obtained from reduction of complex 1 by [Na][biphenyl], was converted into complex [Fe[sub4]S[sub4](NO)[sub4]][sup2-] (3) along with byproduct [(NO)[sub2]Fe(SR)[sub2]][sup-] via the proposed [Fe[sub4]S[sub3](SPh)(NO)[sub4]][sup2-] intermediate upon treating complex 2 with 1.5 equiv of [Fe(SPh)[sub4]][sup2-] and the subsequent addition of 1/8 equiv of S[sub8] in CH[sub3]CN at ambient temperature. Complex 3 was characterized by IR, UV-vis, and single-crystal X-ray diffraction. Upon addition of complex 3 to the CH[sub3]CN solution of [Fe(SPh)[sub4]][sup-] in a 1:2 molar ratio at ambient temperature, the rapid NO radical-thiyl radical exchange reaction between complex 3 and the biomimetic oxidized form of rubredoxin [Fe(SPh)[sub4]][sup-] occurred, leading to the simultaneous formation of [4Fe-4S] cluster [Fe[sub4]S[sub4](SPh)[sub4]][sup2-] (5) and DNIC [(NO)[sub2]Fe(SPh)[sub2]][sup-]. This result demonstrates a successful biomimetic reassembly of [4Fe-4S] cluster [Fe[sub4]S[sub4](SPh)[sub4]][sup2-] from NO-modified [Fe-S] clusters, relevant to the repair of DNICs derived from nitrosylation of [4Fe-4S] clusters of endonuclease Ill back to [4Fe-45] clusters upon addition of ferrous ion, cysteine, and lscS.
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