Phosphine-substituted Fe-Te clusters related to the active site of [FeFe]-H2ases

In order to enrich the chemistry of the Fe/Te cluster compounds related to the active site of the [FeFe]-hydrogenase, the reactions of compound Fe-2(mu-TeAr)(2)(CO)(6)with tertiary phosphines were described. Three types of novel phosphine substituted Fe/Te model compounds were successfully prepared. That is, the treatment of Fe-2(mu-TeAr)(2)(CO)(6)(Ar = C(6)H(5)A, C6H4-F-4B) with 2 equivalents of PPh(3)under UV conditions produced dinuclear compounds Fe-2(mu-TeC6H5)(2)(CO)(4)(PPh3)(2)(1) and Fe-2(mu-TeC6H4-F-4)(2)(CO)(4)(PPh3)(2)(2) in moderate yields together with unusual tetranuclear compounds Fe-4(mu-TeC6H5)(6)(CO)(6)(PPh3)(2)(3) and Fe-4(mu-TeC6H4-4-F)(6)(CO)(6)(PPh3)(2)(4). Thesyn- andanti-isomers of1and2were isolated in the solid state using the TLC method. Furthermore, the reaction of Fe-2(mu-TeAr)(2)(CO)(6)and 4 equivalents of PMe(3)gave new types of mononuclear PMe3-disubstituted compounds Fe(TeC6H5)(2)(CO)(2)(PMe3)(2)(5) and Fe(TeC6H4-4-F)(2)(CO)(2)(PMe3)(2)(6) which could mimic Fe(d)of the [FeFe]-hydrogenase. All the new compounds were fully characterized by elemental analysis, IR, NMR spectroscopy, UV-Visible absorption and particularly some of them by X-ray crystallography. The electrochemical properties of1,2,5and6were also investigated, demonstrating that these compounds can be considered as electrochemical catalysts for the hydrogen evolution reaction. According to the electrochemical behavior of5and6, a CEECC mechanism was proposed for the catalytic process.