Designed Synthesis Of New Fe/E (E=S,Se) Cluster Compounds Related To [FeFe]-Hydrogenase Active Site

The [FeFe]-hydrogenases are highly efficient enzymes that catalyze the reduction of proton to hydrogen and the oxidation of hydrogen in microorganisms, so studies on biomimetic chemistry of [FeFe]-hydrogenases have important theoretical significance and practical applications. In order to develop biomimetic chemistry of [FeFe]-hydrogenases and synthetic chemistry of metal clusters, we initiated a study concerning the synthesis, structure and properties of a series of new butterfly Fe/E(E =S, Se) cluster compounds related to the [FeFe]-hydrogenase active site. The main results described in this thesis are as follows:1. A total of 28 new compounds have been successfully synthesized, including 19 [FeFe]-hydrogenase active site model compounds and 9 novel butterfly Fe/E(E= S, Se) cluster compounds. The structures of these new compounds were fully characterized by elemental analysis, IR, and 1H NMR, as well as for some of them by 13C NMR,31P NMR,77Se NMR, MS and cyclic voltammetry. The crystal structures of 15 compounds were determined by X-ray diffraction method.2. The parent PDT-type model complex with a bis(hydroxymethyl) functionality [(μ-SCH2)2C(CH2OH)2]Fe2(CO)6 (1) was first prepared, and a series of its functional derivatives [(μ-SCH2)2C(CH2OH)(CH2OCOCH3)]Fe2(CO)6(2),[(μ-SCH2)2C(CH2O COCH3)2]Fe2(CO)6 (3), [(μ-SCH2)2C(CH2OCOC5H4N-4)2]Fe2(CO)6 (4), [(μ-SCH2)2C (CH2OCOC5H4N-3)2]Fe2(CO)6(5), [(μ-SCH2)2C(CH2OCOC6H4PPh2-2)2]Fe2(CO)6(6), [(μ-SCH2)2C(CH2OCOC6H4PPh2-3)2]Fe2(CO)6(7), [(μ-SCH2)2C(CH2OH)(CH2OCO C6H4PPh2-3)]2[Fe2(CO)6]2(7a), [(μ-SCH2)2C(CH2OH)(CH2OCOC6H4PPh2-3)]Fe2 (CO)6(8), [(μ-SCH2)2C(CH2OCOC6H4PPh2-4)2]Fe2(CO)6(9) and [(μ-SCH2)2C(CH2O COCH2PPh2)2]Fe2(CO)6(10) were prepared. All of these new compounds were fully characterized by elemental analysis, IR and 1H NMR spectroscopies, as well as for 6-10 by 31P NMR and the molecular structures of 1,2,3,5 and 7a were confirmed by X-ray diffraction techniques. The electrochemical study indicated that model compound 1 can catalyze reduction of acetic acid protons to H2 under CV conditions. The mechanism for this electrocatalytic process is proposed.3. The ADT-type model complex containing serine framework{μ-SCH2N[CH (CH2OH)(CO2CH3)]CH2S-μ}[Fe2(CO)6] (A) was first prepared, and its four derivatives{μ-SCH2N[CH(CH2OPPh2)(CO2CH3)]CH2S-μ}[Fe2(CO)5] (1),{μ-SCH2N [CH(CH2OTs)(CO2CH3)]CH2S-μ}[Fe2(CO)6](2),{μ-SCH2N[CH(CH2OMs)(CO2CH3 )]CH2S-μ}[Fe2(CO)6] (3),{μ-SCH2N[C(CH2)(CO2CH3)]CH2S-μ}[Fe2(CO)6] (4) were prepared through its functional transformation reactions. These new compounds were characterized by elemental analysis, IR and 1H NMR spectroscopies, as well as for 4 by 13C NMR and the molecular structures of 2 and 4 were confirmed by X-ray diffraction techniques.In addition, the model compound [Et4N]2[Fe4S4(TriS)]{Fe2N(CH2S-μ)2(CH2CH2S) (CO)5}(5), which contains the whole skeletal structure of the active site of [FeFe]-hydrogenases was synthesized through ester exchange and decarbonylation reactions of [(μ-SCH2)2NCH2CH2SC(O)CH3]Fe2(CO)6 with the cubane cluster [Et4N]2[Fe4S4(TriS)(t-BuS)]. This new compound was characterized by elemental analysis, IR,1H NMR and cyclic voltammetry.The new parent ADT-type model complex {μ-SCH2N[C(CH2OH)2CH3]CH2S-μ} [Fe2(CO)6](6) was also prepared, and its derivative{μ-SCH2N[C(CH2OCOCH3)2CH3] CH2S-μ}Fe2(CO)6 (7) was synthesized by reaction of 6 with CH2(COOH)2. Compounds 6 and 7 were characterized by elemental analysis, IR and 1H NMR spectroscopies and the structure of 7 was confirmed by X-ray diffraction technique.4. Seven new butterfly Fe/S cluster complexes [μ-S=C-S-Mo(CO)3(C5H4COO CH3)](μ-SEt)[Fe2(CO)6](la), [μ-S=C-S-Mo(CO)3(C5H4COOCH3)](μ-S-tBu)[Fe2 (CO)6] (lb), [μ-S=C-S-W(CO)3(C5H4COCH3)](μ-SEt)[Fe2(CO)6] (2a),[μ-S=C-S-W (CO)3(C5H4COCH3)](μ-S-tBu)[Fe2(CO)6](2b), [(μ-S=C-S-Mo(CO)3(C5H4COOCH3) Fe2(CO)6]2(μ-SCH2CH2OCH2CH2S-μ)(3), [(μ-S=C-S-W(CO)3(C5H4COCH3)Fe2 (CO)6]2(μ-SCH2CH2OCH2CH2S-μ)(4)and{(μ-SEt)(μ4-S)[Fe2(CO)6]2]}[μ-S-W(CO)3 (C5H4COCH3)] (5) were produced by reactions of electrophiles (C5H4COOCH3)Mo (CO)3I or (C5H4COCH3)W(CO)3I with the corresponding anionic salts (μ-SR)(μ-SCS")Fe2(CO)6(Et3NH)(B),(μ-S-CH2CH2OCH2CH2-S-μ)[(μ-SCS-)Fe2 (CO)6]2(Et3NH)2(D) and (μ-SEt)(μ4-S))(μ-S-)[Fe2(CO)6]2(Et3NH) (E). These products were characterized by elemental analysis, IR and 1H NMR. The structures of la and 2a were confirmed by X-ray diffraction techniques.5. Two new Fe/Se cluster complexes (μ-SeEt)(μ-SePh2P-μ)Fe2(CO)6 (1) and (μ-SeEt){μ-Se[(CH3)2CH]2P-μ)Fe2(CO)6 (2) were first prepared, and they were characterized by elemental analysis, IR,1H NMR,31P NMR and 77Se NMR spectroscopies and the structure of 1 was confirmed by X-ray diffraction technique.In addition, the molecular structures of four compounds prepared by others in our group were confirmed by X-ray diffraction techniques.