C=N Bond Activation and Hydration by an Iron(III) Complex with Asymmetric Sulfur Oxygenation

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• 作者：Yun-Ru Wu ; Chia-Ming Chang ; Chia-Chi Wang ; Chang-Chih Hsieh and Yih-Chern Horng
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：2017
• 期：4
• 页码：840-843
• 全文大小：731K
• ISSN：1099-0682c

文摘

The presence of asymmetric cysteine sulfur-oxygenation donors, consisting of sulfenate (SO), sulfinate (SO₂), and thiolate (S), around a trivalent iron is essential for the catalytic function of Fe- or Co-type nitrile hydratase (NHase). To gain insight into the role of this asymmetric ligation, an octahedral bisthiolate low-spin Fe^III complex and two of its S-oxygenation derivatives, unprecedented mixed sulfinate/thiolate and O-bound bissulfinate complexes, were generated. The placement of anionic nitrogen atoms trans to the thiolates in the bisthiolate complex caused the axial imino C=N bonds to be more polarized and thus resembled the activation of bound nitrile in nitrile hydratase. The polarization was found to be even more severe in the monosulfinate species, and hydration of the Fe-bound C=N bond by HO^– was observed. The generation of an O-bound bissulfinate octahedral complex implied that the equatorial carboxamido and axial thiolate ligation in Fe-NHase provided greater electron buffering capacity in keeping the electron density of the Fe^III ion constant even in the presence of equatorial S-oxygenations.