Diferrous Cyanides as Models for the Fe-only Hydrogenases

The first systematic study of diferrous dicyano dithiolates is described. Oxidation of [Fe2(S2C2H4)(CN)2(CO)4]2- in the presence of cyanide and tertiary phosphines and of Fe2(S2C2H4)(CO)4(PMe3)2 in the presence of cyanide affords a series of diferrous cyanide derivatives that bear a stoichiometric,...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2005-08, Vol.127 (31), p.11010-11018
Main Authors: Boyke, Christine A, van der Vlugt, Jarl Ivar, Rauchfuss, Thomas B, Wilson, Scott R, Zampella, Giuseppe, De Gioia, Luca
Format: Article
Language:English
Subjects:
Bioinorganic chemistry
Chemistry
Cyanides - chemistry
Exact sciences and technology
Ferrous Compounds - chemistry
Hydrogenase - chemistry
Inorganic chemistry and origins of life
Iron-Sulfur Proteins - chemistry
Models, Chemical
Protein Conformation
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Summary:The first systematic study of diferrous dicyano dithiolates is described. Oxidation of [Fe2(S2C2H4)(CN)2(CO)4]2- in the presence of cyanide and tertiary phosphines and of Fe2(S2C2H4)(CO)4(PMe3)2 in the presence of cyanide affords a series of diferrous cyanide derivatives that bear a stoichiometric, structural, and electronic relationship to the Hox air state of the Fe-only hydrogenases. With PPh3 as the trapping ligand, we obtained an unsymmetrical isomer of Fe2(S2C2H4)(μ-CO)(CN)2(PPh3)2(CO)2, as confirmed crystallographically. This diferrous cyanide features the semibridging CO-ligand, with Fe-μC bond lengths of 2.15 and 1.85 Å. Four isomers of Fe2(S2C2H4)(μ-CO)(CN)2(PMe3)2(CO)2 were observed, the initial product again being unsymmetrical but more stable isomers being symmetrical. DFT calculations confirm that the most stable isomers of Fe2(S2C2H4)(μ-CO)(CN)2(PMe3)2(CO)2 have cyanide trans to μ-CO. Oxidative decarbonylation also afforded the new tetracyanide [Fe2(S2C2H4)(μ-CO)(CN)4(CO)2]2-. Insights into the oxidative decarbonylation mechanism of these syntheses come from the spectroscopic characterization of the tetracarbonyl [Fe2(S2C2H4)(μ-CO)(CN)3(CO)3]-. This species reacts with PEt3 to produce the stable adduct [Fe2(S2C2H4)(μ-CO)(CN)3(CO)2(PEt3)]-.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja051584d