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Sulfur versus iron oxidation in an Iron-Thiolate model complex

Title
Sulfur versus iron oxidation in an Iron-Thiolate model complex
Authors
McDonald A.R.Bukowski M.R.Farquhar E.R.Jackson T.A.Koehntop K.D.Seo M.S.De Hont R.F.Stubna A.Halfen J.A.Munck E.Nam W.Que Jr. L.
Ewha Authors
남원우서미숙
SCOPUS Author ID
남원우scopus
Issue Date
2010
Journal Title
Journal of the American Chemical Society
ISSN
0002-7863JCR Link
Citation
vol. 132, no. 48, pp. 17118 - 17129
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
In the absence of base, the reaction of [Fe II(TMCS)]PF 6 (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11- tetraazacyclotetradecane) with peracid in methanol at -20 °C did not yield the oxoiron(IV) complex (2, [Fe IV(O)(TMCS)]PF 6), as previously observed in the presence of strong base (KO tBu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe II(TMCS) + 2O] +, while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 Å, Fe-S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe=O = 1.64 Å) and resonance Raman (v Fe=O = 831 cm -1) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety (v s(SO 2) ≈ 1000 cm -1, v as(SO 2) ≈ 1150 cm -1). Investigations into the reactivity of 1 and 2 toward H + and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3. © 2010 American Chemical Society.
DOI
10.1021/ja1045428
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자연과학대학 > 화학·나노과학전공 > Journal papers
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