The reaction of electrophiles with models of iron–iron hydrogenase: A switch in regioselectivity

详细信息    查看全文

• 作者：Jesse W. Tye ; Marcetta Y. Darensbourg and Michael B. Hall
• 关键词：Hydrogenase ; Enzyme model complexes ; Iron– ; carbonyl complexes
• 刊名：Journal of Molecular Structure: THEOCHEM
• 出版年：2006
• 出版时间：12 October 2006
• 年：2006
• 卷：771
• 期：1-3
• 页码：123-128
• 全文大小：301 K

文摘

Simple dithiolate-bridged dinuclear iron clusters of the form (μ-S(CH₂)_xS)[Fe(CO)₂(PR₃)]₂ act as models of the active site of the enzyme iron-iron hydrogenase ([FeFe]H₂ase). These complexes have been shown react with the electrophilic species, H⁺ and Et⁺ with differing regioselectivity; H⁺ reacts to form a 3c–2e⁻ Fe–H–Fe bond, while Et⁺ reacts to form a new C–S bond. We have used density functional theory (DFT) calculations to examine the reaction of these two electrophilic species using the computational model (μ-SCH₂CH₂S)[Fe(CO)₂(PH₃)]₂. In agreement with the experimental results, protonation of the Fe–Fe bond density is found to yield a much more stable complex than protonation of a bridging sulfur atom, while alkylation of a sulfur atom of the bridging thiolate is found to yield a much more stable complex than alkylation of the iron centers. Additional computations show that a mononuclear iron(II) complex with an Fe–E bond (E=H or Et) is significantly more stable than its constitutional isomer with iron(0) and an S–E bond. The instability of a bridging ethyl complex is attributed to the inability of the ethyl group, in contrast to a hydride, to form a stable 3c–2e⁻ bond with the two iron centers.