[FeFe]-Hydrogenase H-Cluster Mimics with Unique Planar μ-(SCH₂)₂ER₂ Linkers (E=Ge and Sn)

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• 作者：M. Sc. Hassan Abul-Futouh ; Dr. Laith R. Almazahreh ; Dr. Takahiro Sakamoto ; Prof. Dr. Nhu Y. T. Stessman ; Prof. Dr. Dennis L. Lichtenberger ; Prof. Dr. Richard S. Glass ; Dr. Helmar Gö ; rls ; Prof. Dr. Mohammad El-Khateeb ; Prof. Dr. Philippe Schollhammer ; Prof. Dr. Grzegorz Mloston and Prof. Dr. Wolfgang Weigand
• 刊名：Chemistry - A European Journal
• 出版年：2017
• 出版时间：January 5, 2017
• 年：2017
• 卷：23
• 期：2
• 页码：346-359
• 全文大小：3980K
• ISSN：1521-3765

文摘

Analogues of the [2Fe-2S] subcluster of hydrogenase enzymes in which the central group of the three-atom chain linker between the sulfur atoms is replaced by GeR₂ and SnR₂ groups are studied. The six-membered FeSCECS rings in these complexes (E=Ge or Sn) adopt an unusual conformation with nearly co-planar SCECS atoms perpendicular to the Fe-Fe core. Computational modelling traces this result to the steric interaction of the Me groups with the axial carbonyls of the Fe₂(CO)₆ cluster and low torsional strain for GeMe₂ and SnMe₂ moieties owing to the long C−Ge and C−Sn bonds. Gas-phase photoelectron spectroscopy of these complexes shows a shift of ionization potentials to lower energies with substantial sulfur orbital character and, as supported by the computations, an increase in sulfur character in the predominantly metal–metal bonding HOMO. Cyclic voltammetry reveals that the complexes follow an ECE-type reduction mechanism (E=electron transfer and C=chemical process) in the absence of acid and catalysis of proton reduction in the presence of acid. Two cyclic tetranuclear complexes featuring the sulfur atoms of two Fe₂S₂(CO)₆ cores bridged by CH₂SnR₂CH₂, R=Me, Ph, linkers were also obtained and characterized.