Protonation of Nickel鈥揑ron Hydrogenase Models Proceeds after Isomerization at Nickel

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• 作者：Mioy T. Huynh ; David Schilter ; Sharon Hammes-Schiffer ; Thomas B. Rauchfuss
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：September 3, 2014
• 年：2014
• 卷：136
• 期：35
• 页码：12385-12395
• 全文大小：542K
• ISSN：1520-5126

文摘

Theory and experiment indicate that the protonation of reduced NiFe dithiolates proceeds via a previously undetected isomer with enhanced basicity. In particular, it is proposed that protonation of (OC)₃Fe(pdt)Ni(dppe) (1; pdt^{2鈥?/sup> = 鈥?/sup>S(CH₂)₃S鈥?/sup>; dppe = Ph₂P(CH₂)₂PPh₂) occurs at the Fe site of the two-electron mixed-valence Fe(0)Ni(II) species, not the Fe(I)-Ni(I) bond for the homovalence isomer of 1. The new pathway, which may have implications for protonation of other complexes and clusters, was uncovered through studies on the homologous series L(OC)₂Fe(pdt)M(dppe), where M = Ni, Pd (2), and Pt (3) and L = CO, PCy₃. Similar to 1, complexes 2 and 3 undergo both protonation and 1e鈥?/sup> oxidation to afford well-characterized hydrides ([2H]+ and [3H]+) and mixed-valence derivatives ([2]+ and [3]+), respectively. Whereas the Pd site is tetrahedral in 2, the Pt site is square-planar in 3, indicating that this complex is best described as Fe(0)Pt(II). In view of the results on 2 and 3, the potential energy surface of 1 was reinvestigated with density functional theory. These calculations revealed the existence of an energetically accessible and more basic Fe(0)Ni(II) isomer with a square-planar Ni site.}