American Chemical Society
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Synthesis, Structure, and Electrocatalysis of Diiron C-Functionalized Propanedithiolate (PDT) Complexes Related to the Active Site of [FeFe]-Hydrogenases

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Version 2 2016-06-03, 22:22
Version 1 2016-02-27, 12:39
posted on 2008-06-02, 00:00 authored by Li-Cheng Song, Chang-Gong Li, Jie Gao, Bang-Shao Yin, Xiang Luo, Xiao-Guang Zhang, Hai-Lin Bao, Qing-Mei Hu
New C-functionalized propanedithiolate-type model complexes (18) have been synthesized by functional transformation reactions of the known complex [(μ-SCH2)2CH(OH)]Fe2(CO)6 (A). Treatment of A with the acylating agents PhC(O)Cl, 4-pyridinecarboxylic acid chloride, 2-furancarbonyl chloride, and 2-thiophenecarbonyl chloride in the presence of Et3N affords the expected C-functionalized complexes [(μ-SCH2)2CHO2CPh]Fe2(CO)6 (1), [(μ-SCH2)2CHO2CC5H4N-4]Fe2(CO)6 (2), [(μ-SCH2)2CHO2CC4H3O-2]Fe2(CO)6 (3), and [(μ-SCH2)2CHO2CC4H3S-2]Fe2(CO)6 (4). However, when A is treated with the phosphatizing agents Ph2PCl, PCl3 and PBr3, both C- and Fe-functionalized complexes [(μ-SCH2)2CHOPPh21]Fe2(CO)5 (5), [(μ-SCH2)2CHOPCl21]Fe2(CO)5 (6), and [(μ-SCH2)2CHOPBr21]Fe2(CO)5 (7) are unexpectedly obtained via intramolecular CO substitution by P atoms of the initially formed phosphite complexes. The simplest C-functionalized model complex [(μ-SCH2)2CO]Fe2(CO)6 (8) can be produced by oxidation of A with Dess−Martin reagent. While 8 is found to be an electrocatalyst for proton reduction to hydrogen, starting complex A can be prepared by another method involving the reaction of HC(OH)(CH2Br)2 with the in situ generated (μ-LiS)2Fe2(CO)6. X-ray crystallographic studies reveal that the bridgehead C atom of 8 is double-bonded to an O atom to form a ketone functionality, whereas the bridgehead C atoms of A, 1, 3, and 4 are equatorially-bonded to their functionalities and those of 57 axially-bonded to their functionalities due to formation of the corresponding P−Fe bond-containing heterocycles.