Syntheses,Structures And Properties Of Iron Sulfur And Iron Selenium Clusters

Hydrogenases,a type of biometalloenzymes,can reversibly catalyze proton reduction to dihydrogen.Because of promising applications in new energy sources,they have attracted considerable attention from organometallic and bioinorganic chemists.To data,mimicking hydrogenases is mainly carried out in the following two aspects:one is to structurally and functionally simulate the hydrogenase active centers;the other is to synthesize Fe/E(E = S,Se,Te)clusters with a view to modeling functionally the acive sites of hydrogenases.On one hand,we can better study catalytic mechanisms at the molecular level.On the other hand,we wish to screen out model compounds with H2-producing catalytic activity to solve the increasingly serious energy crisis.In order to enrich and develop the research of iron sulfur and iron selenium clusters related to hydrogenase,we have designed and synthesized a series of new Fe/E(E=S,Se)clusters containing phosphine ligand.Their structures and electrochemical properties have been studied in this thesis.The main results are described as follows:1.The three-component reactions of PhNHC(=S)OR,Et3N and Fe3(CO)12 in THF afford the[Et3NH]+ salt of the[(μ-PhN=COR)Fe2(CO)6(μ-S-)]cluster anion(R = CH3,CH2Ph).The S-centered cluster anion reacts with CH3I to give[(μ-k2N,C-PhN=COR)Fe2(CO)6(μ-SCH3)](1,R=CH3;3,R = CH2Ph)and[(μ-k2N,C-PhN=COCH3)Fe2(CO)6(μ4-S)Fe2(CO)6(μ-SCH3)](2).Further reactions of 1 with 1 equiv of PPh2R in the presence of Me3NO lead to the corresponding monophosphine-substituted complexes[(μ-k2N,C-PhN=COCH3)Fe2(CO)5(L)(μ-SCH3)](4,L =PPh3;5,L = PPh2Py).Similarly,reactions of 3 with PPh2R produce the corresponding monophosphine-substituted complexes[(p-k2N,C-PhN=COCH2Ph)Fe2(CO)5(L)(μ-SCH3)](6,L=PPh3;8,L = PPh2Py)besides an unexpected monophosphine-disubstituted complex[(μ-k2N,C-PhN=COCH2Ph)Fe2(CO)4(PPh3)2(μ-SCH3)](7).All the new complexes have been characterized by elemental analyses,IR and NMR spectroscopy and structurally determined by X-ray crystallography.Electrochemical studies indicate that when using HOAc or TFA as a proton source,complexes 1,4-6 and 8 exhibit catalytic H2 production.We can see that the electrocatalytic activities of the compounds are different under the same concentration and test condition.The catalytic activity of PPh3 substituted compound 4 is higher than that of compound 1,indicating that phosphine ligand has a certain catalytic effect on the proton reduction ability of the compound.2.The three-component reactions of ArNHC(=Se)OCH3,Et3N and Fe3(CO)12 afford the[Et3NH]+ salt of the[(μ-ArN=COCH3)Fe2(CO)6(μ-Se-)]cluster anion.The Se-centered cluster anion reacts with CH3I to give two pairs of isomers[(μ-k2N,C-ArN=COR)Fe2(CO)6(μ-SeCH3)](9-e,9-a,Ar = C6H4)and[(μ-k2N,C-ArN=COR)Fe2(CO)6(μ-SeCH3)](10-e,10-a,Ar =4-CIC6H4).Furthermore,trapping the Se-centered cluster anion[(μ-ArN=COR)Fe2(CO)6(μ-Se-)]with PPh2Cl offers[(μ-k2N,C-ArN=COR)Fe2(CO)6(μ-k2Se,P-SePPh2)](11,Ar = C6H5,13,Ar ＝4-ClC6H4,R = CH3;12,Ar = C6H5,14,Ar = 4-ClC6H4,R = CH2Ph).Reactions of 9 with monophosphine L lead to the corresponding substituted complexes[(μ-k2N,C-PhN=COCH3)Fe2-(CO)5(L)(μ-SeCH3)](15-e,15-a,L = PPh3;16-e,L = PPh2Py).All the new complexes have been completely characterized by elemental analyses,IR,NMR spectroscopy and structurally determined by X-ray crystallography.Electrochemical studies reveal that when using HOAc or TFA as a proton source,all of the complexes can catalyze H2 production.We can see that the catalytic activities of PPh3 and PPh2Py substituted compounds 15-a and 16-e don’t increase significantly compared with compound 9-e under the same concentration and test condition,which is different from the previous chapter,indicating that iron-selenium compounds and iron-sulfide compounds have different electrochemical catalytic property.3.Reaction of base-containing diphosphine ligand NPS2(NP2 =(Ph2PCH2)2NCH3)with[Fe3(CO)12]in THF at room temperature forms[｛Fe2(CO)6(μ-PPh2)｝2(μ4-S2)](17)and[Fe3(CO)8(μ3-S)2{PPh2[N(CH3)(CH2P(=S)Ph2)]}](18).Similarly,NPSe2 reacts with Fe3(CO)12 to provide[{Fe2(CO)6(μ-PPh2)}2(μ4-Se2)](19)and[Fe3(CO)7(μ3-Se)2{k2P,P-(PPh2CH2)2NCH3}](20).All the compounds have been completely characterized by elemental analyses,IR,NMR spectroscopy and structurally determined by X-ray crystallography.Electrochemical studies reveal that when using HOAc or TFA as a proton source,18 and 20 exhibit catalytic H2 production.4.Reactions of Ph2PCSNHR with[Cp2Fe2(CO)4]in refluxing toluene afford complexes[CpFe(CO)(μ-PPh2)(μ-SPPh2)Fe(CO)Cp](21)and[Cp2Fe2(CO)2(μ-CNR)2](22,R = Ph).Unlike Ph2PCSNHR,reactions of Ph2P(S)CSNHR with[Cp2Fe2(CO)4]under the same conditions give[CpFe(CO)2(kP-P(=S)Ph2)](23)and[CpFe(CO)(kP-P(=S)Ph2)(μ-CNR)](24,R = Ph,25,R = Et)Interestingly,Ph2P(S)CSNHPy generates[CpFe(CO)2(kP-P(=S)Ph2)](23)and[C5H3(CH=NPy)-(CHNHPy)](26).Upon treating with NiCl2·6H2O,26 produces[C5H3(CHNHPy)(CHO)](27).All the new compounds have been characterized by elemental analyses,IR,NMR spectroscopy and structurally determined by X-ray crystallography.Electrochemical studies indicate that using HO Ac as a proton source complexes 21,23 and 25 can catalyze H2 production.We can see that the electrocatalytic activities of compounds 23 and 25 are quite different under the same concentration and test conditions,and the catalytic activity of EtNC substituted compound 25 is obviously higher than that of compound 23,indicating that the isonitrile ligand has a strong catalytic effect on the proton reduction ability.5.Reaction of Ph2P(Se)CSNHPh with Cp2Fe2(CO)4 in refluxing toluene affords[CpFe(CO)(k2P,S-Ph2PC(S)=NPh)](28)and[CpFe(CO)2(kP-P(=Se)Ph2)](29).Further,reactions of 29 with 1 equiv of PPh2R in the presence of Me3NO generate[CpFe(CO)(kSe-SeP(=Se)Ph2)(L)](30,L = PPh3;31,L = PPh2Py).Unlike 29,reactions of[CpFe(CO)2(kP-P(=S)Ph2)]with PPh2R under the same conditions give the corresponding phosphine-substituted complexes[CpFe(CO)(kP-P(=S)Ph2)(L)](32,L = PPh3;33,L = PPh2Py).All the new compounds have been characterized by elemental analyses,IR,NMR spectroscopy and structurally determined by X-ray crystallography.Electrochemical studies indicate that using HOAc or TFA as a proton source complexes 28-33 can catalyze H2 production.We can see that there are some differences in the electrocatalytic activity between the phosphine ligand substituted compounds under the same concentration and test condition.The catalytic activity of PPh3 substituted compound 30 is higher than that of PPh2Py substituted compound 31.