Portal de Periódicos da CAPES

Diferrous Cyanides as Models for the Fe-only Hydrogenases

2005; American Chemical Society; Volume: 127; Issue: 31 Linguagem: Inglês

10.1021/ja051584d

1943-2984

C.A. Boyke, Jarl Ivar van der Vlugt, Thomas B. Rauchfuss, Scott R. Wilson, Giuseppe Zampella, Luca De Gioia,

Carbon dioxide utilization in catalysis

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 Hoxair 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)]-.