Synthesis and structural characterization of the mono- and diphosphine-containing diiron propanedithiolate complexes related to [FeFe]-hydrogenases. Biomimetic H-2 evolution catalyzed by (mu-PDT)Fe-2(CO)(4)[(Ph2P)(2)N(n-Pr)]

摘要

As the new H-cluster models, six diiron propanedithiolate (PDT) complexes with mono- and diphosphine ligands have been prepared and structurally characterized. The monophosphine model complex (mu-PDT)Fe-2(CO)(5)[Ph2PNH(t-Bu)] (1) was prepared by reaction of parent complex (mu-PDT)Fe-2(CO)(6) (A) with 1 equiv of Ph2PNH(t-Bu) in refluxing xylene, whereas A reacted with 1 equiv of Me3NO center dot 2H(2)O in MeCN at room temperature followed by 1 equiv of Ph2PH to give the corresponding monophosphine model complex (mu-PDT)Fe-2(CO)(5)(Ph2PH) (2). Further treatment of 2 with 1 equiv of n-BuLi in THF at -78 degrees C followed by 1 equiv of CpFe(CO)(2)I from -78 degrees C to room temperature afforded monophosphine model complex (p-PDT)Fe-2(CO)(5)[Ph2PFe(CO)(2)Cp] (3), whereas the diphosphine model complexes (mu-PDT)Fe-2(CO)(4)(Ph2PC2H4PPh2) (4), (mu-PDT)Fe-2(CO)(4)[(Ph2P)(2)N(n-Pr)] (5) and (eta-PDT)Fe-2(CO)(4)[(Ph2P)(2)N(n-Bu)] (6) were obtained by reactions of A with ca.1 equiv of the corresponding diphosphines in refluxing xylene. All the new model complexes were characterized by elemental analysis, spectroscopy and particularly for 1 and 3-6 by X-ray crystallography. On the basis of electrochemical and spectroelectrochemical studies, model 5 was found to be a catalyst for HOAc proton reduction to H-2, and for this electrocatalytic reaction an ECCE mechanism was proposed. (C) 2008 Published by Elsevier Inc.