Terminal Thiolate-Dominated H/D Exchanges and H2 Release: Diiron Thiol–Hydride

To determine the reaction pathways at a metal–ligand site in enzymes, we incorporated a terminal thiolate site into a diiron bridging hydride. Trithiolato diiron hydride, (μ-H)­Fe2(pdt)­(dppbz)­(CO)2(SR) (1(μ-H)) [pdt2– = 1,3-(CH2)3S2 2–, dppbz = 1,2-C6H4(PPh2)2, RS– = 1,2-Cy2PC6H4S–)], was synthesi...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2018-09, Vol.140 (36), p.11454-11463
Main Authors: Yu, Xin, Pang, Maofu, Zhang, Shengnan, Hu, Xinlong, Tung, Chen-Ho, Wang, Wenguang
Format: Article
Language:English
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Summary:To determine the reaction pathways at a metal–ligand site in enzymes, we incorporated a terminal thiolate site into a diiron bridging hydride. Trithiolato diiron hydride, (μ-H)­Fe2(pdt)­(dppbz)­(CO)2(SR) (1(μ-H)) [pdt2– = 1,3-(CH2)3S2 2–, dppbz = 1,2-C6H4(PPh2)2, RS– = 1,2-Cy2PC6H4S–)], was synthesized directly by photoassisted oxidative addition of 1,2-Cy2PC6H4SH to Fe2(pdt)­(dppbz)­(CO)4. The terminal thiolate in 1(μ-H) undergoes protonation, affording a thiol–hydride complex [1(μ-H)­H]+. Placing an acidic SH site adjacent to the Fe–H–Fe site allows intramolecular thiol–hydride coupling and releases H2 from [1(μ-H)­H]+. A diiron η2-H2 intermediate in the formation of H2 is proposed, and is evidenced by the H/D exchange reactions of [1(μ-H)­H]+ with D2, D2O, and CD3OD. Isotopic exchange in [1(μ-D)­H]+ is driven by an equilibrium isotope effect with 2.1 kJ/mol difference in free energy that favors [1(μ-H)­D]+. [1(μ-H)­H]+ catalyzes H/D scrambling between H2 and D2O or CD3OD to produce HD. The reactions based on such a “proton–hydride” model provide insights into the reversible heterolytic cleavage of H2 by H2ases.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.8b06996