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《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(1):90-98
The two‐step one‐pot oxidative decarbonylation of [Fe2(S2C2H4)(CO)4(PMe3)2] ( 1 ) with [FeCp2]PF6, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2 – 6 , containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1 2+ as the initial intermediate of the oxidation of 1 , even when a deficiency of the oxidant was employed. Subsequent addition of PR3 gave rise to [Fe2(S2C2H4)(μ‐CO)(CO)3(PMe3)3]2+ ( 2 ) and [Fe2(S2C2H4)(μ‐CO)(CO)2(PMe3)2(PR3)2]2+ (R=Me 3 , OMe 4 ) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe2(S2C2H4)(μ‐CO)(CO)2(PMe3)3(MeCN)]2+ ( 5 ) and [Fe2(S2C2H4)(μ‐CO)(CO)(PMe3)4(MeCN)]2+ ( 6 ) were fully characterized. Relevant to the Hred state of the active site of Fe‐only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(8):2208-2211
To understand the molecular details of O2‐tolerant hydrogen cycling by a soluble NAD+‐reducing [NiFe] hydrogenase, we herein present the first bioinspired heterobimetallic S‐oxygenated [NiFe] complex as a structural and vibrational spectroscopic model for the oxygen‐inhibited [NiFe] active site. This compound and its non‐S‐oxygenated congener were fully characterized, and their electronic structures were elucidated in a combined experimental and theoretical study with emphasis on the bridging sulfenato moiety. Based on the vibrational spectroscopic properties of these complexes, we also propose novel strategies for exploring S‐oxygenated intermediates in hydrogenases and similar enzymes. 相似文献
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Frontispiece: Heterolytic Cleavage of Hydrogen by an Iron Hydrogenase Model: An Fe‐H⋅⋅⋅H‐N Dihydrogen Bond Characterized by Neutron Diffraction
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Dr. Tianbiao Liu Dr. Xiaoping Wang Dr. Christina Hoffmann Dr. Daniel L. DuBois Dr. R. Morris Bullock 《Angewandte Chemie (International ed. in English)》2014,53(21)
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Heterolytic Cleavage of Hydrogen by an Iron Hydrogenase Model: An Fe‐H⋅⋅⋅H‐N Dihydrogen Bond Characterized by Neutron Diffraction
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Dr. Tianbiao Liu Dr. Xiaoping Wang Dr. Christina Hoffmann Dr. Daniel L. DuBois Dr. R. Morris Bullock 《Angewandte Chemie (International ed. in English)》2014,53(21):5300-5304
Hydrogenase enzymes in nature use hydrogen as a fuel, but the heterolytic cleavage of H? H bonds cannot be readily observed in enzymes. Here we show that an iron complex with pendant amines in the diphosphine ligand cleaves hydrogen heterolytically. The product has a strong Fe‐H???H‐N dihydrogen bond. The structure was determined by single‐crystal neutron diffraction, and has a remarkably short H???H distance of 1.489(10) Å between the protic N‐Hδ+ and hydridic Fe‐Hδ? part. The structural data for [CpFe H (PtBu2NtBu2 H )]+ provide a glimpse of how the H? H bond is oxidized or generated in hydrogenase enzymes. These results now provide a full picture for the first time, illustrating structures and reactivity of the dihydrogen complex and the product of the heterolytic cleavage of H2 in a functional model of the active site of the [FeFe] hydrogenase enzyme. 相似文献
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Dr. Jan H. Blank Dr. Salvador Moncho Allen M. Lunsford Prof. Edward N. Brothers Prof. Marcetta Y. Darensbourg Prof. Ashfaq A. Bengali 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12752-12760
The mechanism and energetics of CO, 1‐hexene, and 1‐hexyne substitution from the complexes (SBenz)2[Fe2(CO)6] (SBenz=SCH2Ph) ( 1 ‐CO), (SBenz)2[Fe2(CO)5(η2‐1‐hexene)] ( 1 ‐(η2‐1‐hexene)), and (SBenz)2[Fe2(CO)5(η2‐1‐hexyne)] ( 1 ‐(η2‐1‐hexyne)) were studied by using time‐resolved infrared spectroscopy. Exchange of both CO and 1‐hexyne by P(OEt)3 and pyridine, respectively, proceeds by a bimolecular mechanism. As similar activation enthalpies are obtained for both reactions, the rate‐determining step in both cases is assumed to be the rotation of the Fe(CO)2L (L=CO or 1‐hexyne) unit to accommodate the incoming ligand. The kinetic profile for the displacement of 1‐hexene is quite different than that for the alkyne and, in this case, both reaction channels, that is, dissociative (SN1) and associative (SN2), were found to be competitive. Because DFT calculations predict similar binding enthalpies of alkene and alkyne to the iron center, the results indicate that the bimolecular pathway in the case of the alkyne is lower in free energy than that of the alkene. In complexes of this type, subtle changes in the departing ligand characteristics and the nature of the mercapto bridge can influence the exchange mechanism, such that more than one reaction pathway is available for ligand substitution. The difference between this and the analogous study of (μ‐pdt)[Fe(CO)3]2 (pdt=S(CH2)3S) underscores the unique characteristics of a three‐atom S?S linker in the active site of diiron hydrogenases. 相似文献
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A [RuRu] Analogue of an [FeFe]‐Hydrogenase Traps the Key Hydride Intermediate of the Catalytic Cycle
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Constanze Sommer Dr. Casseday P. Richers Prof. Dr. Wolfgang Lubitz Prof. Dr. Thomas B. Rauchfuss Dr. Edward J. Reijerse 《Angewandte Chemie (International ed. in English)》2018,57(19):5429-5432
The active site of the [FeFe]‐hydrogenases features a binuclear [2Fe]H sub‐cluster that contains a unique bridging amine moiety close to an exposed iron center. Heterolytic splitting of H2 results in the formation of a transient terminal hydride at this iron site, which, however is difficult to stabilize. We show that the hydride intermediate forms immediately when [2Fe]H is replaced with [2Ru]H analogues through artificial maturation. Outside the protein, the [2Ru]H analogues form bridging hydrides, which rearrange to terminal hydrides after insertion into the apo‐protein. H/D exchange of the hydride only occurs for [2Ru]H analogues containing the bridging amine moiety. 相似文献
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Hydrophilic Quaternary Ammonium‐Group‐Containing [FeFe]‐Hydrogenase Models: Synthesis,Structures, and Electrocatalytic Hydrogen Production
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Prof. Li‐Cheng Song Yong‐Xiang Wang Xu‐Kang Xing Shu‐Da Ding Long‐Duo Zhang Xu‐Yong Wang Hong‐Tao Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16304-16314
The first quaternary ammonium‐group‐containing [FeFe]‐hydrogenase models [(μ‐PDT)Fe2(CO)4{κ2‐(Ph2P)2N(CH2)2NMe2BzBr}] ( 2 ; PDT=propanedithiolate) and [(μ‐PDT)Fe2(CO)4{μ‐(Ph2P)2N(CH2)2NMe2BzBr}] ( 4 ) have been prepared by the quaternization of their precursors [(μ‐PDT)Fe2(CO)4{κ2‐(Ph2P)2N(CH2)2NMe2}] ( 1 ) and [(μ‐PDT)Fe2(CO)4{μ‐(Ph2P)2N(CH2)2NMe2}] ( 3 ) with benzyl bromide in high yields. Although new complexes 1 – 4 have been fully characterized by spectroscopic and X‐ray crystallographic studies, the chelated complexes 1 and 2 converted into their bridged isomers 3 and 4 at higher temperatures, thus demonstrating that these bridged isomers are thermodynamically favorable. An electrochemical study on hydrophilic models 2 and 4 in MeCN and MeCN/H2O as solvents indicates that the reduction potentials are shifted to less‐negative potentials as the water content increases. This outcome implies that both 2 and 4 are more easily reduced in the mixed MeCN/H2O solvent than in MeCN. In addition, hydrophilic models 2 and 4 act as electrocatalysts and achieve higher icat/ip values and turnover numbers (TONs) in MeCN/H2O as a solvent than in MeCN for the production of hydrogen from the weak acid HOAc. 相似文献
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Mononuclear Nonheme Iron(III)‐Iodosylarene and High‐Valent Iron‐Oxo Complexes in Olefin Epoxidation Reactions
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Dr. Bin Wang Dr. Yong‐Min Lee Dr. Mi Sook Seo Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2015,54(40):11740-11744
High‐spin iron(III)‐iodosylarene complexes are highly reactive in the epoxidation of olefins, in which epoxides are formed as the major products with high stereospecificity and enantioselectivity. The reactivity of the iron(III)‐iodosylarene intermediates is much greater than that of the corresponding iron(IV)‐oxo complex in these reactions. The iron(III)‐iodosylarene species—not high‐valent iron(IV)‐oxo and iron(V)‐oxo species—are also shown to be the active oxidants in catalytic olefin epoxidation reactions. The present results are discussed in light of the long‐standing controversy on the one oxidant versus multiple oxidants hypothesis in oxidation reactions. 相似文献
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[FeFe] Hydrogenase: Protonation of {2Fe3S} Systems and Formation of Super‐reduced Hydride States
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Aušra Jablonskytė Dr. Joseph A. Wright Dr. Shirley A. Fairhurst Dr. Lee R. Webster Prof. Christopher J. Pickett 《Angewandte Chemie (International ed. in English)》2014,53(38):10143-10146
The synthesis and crystallographic characterization of a complex possessing a well‐defined {2Fe3S(μ‐H)} core gives access to a paramagnetic bridging hydride with retention of the core geometry. Chemistry of this 35‐electron species within the confines of a thin‐layer FTIR spectro‐electrochemistry cell provides evidence for a unprecedented super‐reduced FeI(μ‐H)FeI intermediate. 相似文献
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Identification of HcgC as a SAM‐Dependent Pyridinol Methyltransferase in [Fe]‐Hydrogenase Cofactor Biosynthesis
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Dr. Takashi Fujishiro Liping Bai Dr. Tao Xu Dr. Xiulan Xie Dr. Michael Schick Jörg Kahnt Prof. Dr. Michael Rother Prof. Dr. Xile Hu Dr. Ulrich Ermler Dr. Seigo Shima 《Angewandte Chemie (International ed. in English)》2016,55(33):9648-9651
Previous retrosynthetic and isotope‐labeling studies have indicated that biosynthesis of the iron guanylylpyridinol (FeGP) cofactor of [Fe]‐hydrogenase requires a methyltransferase. This hypothetical enzyme covalently attaches the methyl group at the 3‐position of the pyridinol ring. We describe the identification of HcgC, a gene product of the hcgA‐G cluster responsible for FeGP cofactor biosynthesis. It acts as an S‐adenosylmethionine (SAM)‐dependent methyltransferase, based on the crystal structures of HcgC and the HcgC/SAM and HcgC/S‐adenosylhomocysteine (SAH) complexes. The pyridinol substrate, 6‐carboxymethyl‐5‐methyl‐4‐hydroxy‐2‐pyridinol, was predicted based on properties of the conserved binding pocket and substrate docking simulations. For verification, the assumed substrate was synthesized and used in a kinetic assay. Mass spectrometry and NMR analysis revealed 6‐carboxymethyl‐3,5‐dimethyl‐4‐hydroxy‐2‐pyridinol as the reaction product, which confirmed the function of HcgC. 相似文献
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