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Sulfur versus iron oxidation in an Iron-Thiolate model complex
- Sulfur versus iron oxidation in an Iron-Thiolate model complex
- 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
- 남원우; 서미숙
- SCOPUS Author ID
- Issue Date
- Journal Title
- Journal of the American Chemical Society
- Journal of the American Chemical Society vol. 132, no. 48, pp. 17118 - 17129
- SCI; SCIE; SCOPUS
- Document Type
- 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.
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