ic050108l_si_008.cif (24.56 kB)

Nitrosylated Iron−Thiolate−Sulfinate Complexes with {Fe(NO)}6/7 Electronic Cores:  Relevance to the Transformation between the Active and Inactive NO-Bound Forms of Iron-Containing Nitrile Hydratases

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posted on 19.09.2005, 00:00 by Chien-Ming Lee, Chien-Hong Chen, Hao-Wen Chen, Jo-Lu Hsu, Gene-Hsiang Lee, Wen-Feng Liaw
The five-coordinated iron−thiolate nitrosyl complexes [(NO)Fe(S,S-C6H3R)2]- (R = H (1), m-CH3 (2)), [(NO)Fe(S,S-C6H2-3,6-Cl2)2]- (3), [(NO)Fe(S,S-C6H3R)2]2- (R = H (10), m-CH3 (11)), and [(NO)Fe(S,S-C6H2-3,6-Cl2)2]2- (12) have been isolated and structurally characterized. Sulfur oxygenation of iron−thiolate nitrosyl complexes 13 containing the {Fe(NO)}6 core was triggered by O2 to yield the S-bonded monosulfinate iron species [(NO)Fe(S,SO2-C6H3R)(S,S-C6H3R)]- (R = H (4), m-CH3 (5)) and [(NO)Fe(S,SO2-C6H2-3,6-Cl2)(S,S-C6H2-3,6-Cl2)]22- (6), respectively. In contrast, attack of O2 on the {Fe(NO)}7 complex 10 led to the formation of complex 1 accompanied by the minor products, [Fe(S,S-C6H4)2]22- and [NO3]- (yield 9%). Reduction of complexes 46 by [EtS]- in CH3CN−THF yielded [(NO)Fe(S,SO2-C6H3R)(S,S-C6H3R)]2- (R = H (7), m-CH3 (8)) and [(NO)Fe(S,SO2-C6H2-3,6-Cl2)(S,S-C6H2-3,6-Cl2)]2- (9) along with (EtS)2 identified by 1H NMR. Compared to complex 10, complexes 79 with the less electron-donating sulfinate ligand coordinated to the {Fe(NO)}7 core were oxidized by O2 to yield complexes 46. Obviously, the electronic perturbation of the {Fe(NO)}7 core caused by the coordinated sulfinate in complexes 79 may serve to regulate the reactivity of complexes 79 toward O2. The iron−sulfinate nitrosyl species with the {Fe(NO)}6/7 core exhibit the photolabilization of sulfur-bound [O] moiety. Complexes 14710 (or 25811 and 36912) are interconvertible under sulfur oxygenation, redox processes, and photolysis, respectively.