scholarly journals Electron Redistribution within the Nitrogenase Active Site FeMo-Cofactor During Reductive Elimination of H2 to Achieve N≡N Triple-Bond Activation

2020 ◽  
Vol 142 (52) ◽  
pp. 21679-21690
Author(s):  
Dmitriy A. Lukoyanov ◽  
Zhi-Yong Yang ◽  
Dennis R. Dean ◽  
Lance C. Seefeldt ◽  
Simone Raugei ◽  
...  
Keyword(s):  
Active Site ◽  
Triple Bond ◽  
Bond Activation ◽  
Reductive Elimination ◽  
Femo Cofactor

scholarly journals Comment on “Structural evidence for a dynamic metallocofactor during N2 reduction by Mo-nitrogenase”

Science ◽  
2021 ◽  
Vol 371 (6530) ◽  
pp. eabe5481 ◽  
Author(s):  
John W. Peters ◽  
Oliver Einsle ◽  
Dennis R. Dean ◽  
Serena DeBeer ◽  
Brian M. Hoffman ◽  
...  
Keyword(s):  
Active Site ◽  
Biochemical Evidence ◽  
Mofe Protein ◽  
Femo Cofactor

Kang et al. (Reports, 19 June 2020, p. 1381) report a structure of the nitrogenase MoFe protein that is interpreted to indicate binding of N2 or an N2-derived species to the active-site FeMo cofactor. Independent refinement of the structure and consideration of biochemical evidence do not support this claim.

Exploring the Role of the Central Carbide of the Nitrogenase Active-Site FeMo-cofactor through Targeted 13C Labeling and ENDOR Spectroscopy

2021 ◽  
Author(s):  
Ana Pérez-González ◽  
Zhi-Yong Yang ◽  
Dmitriy A. Lukoyanov ◽  
Dennis R. Dean ◽  
Lance C. Seefeldt ◽  
...  
Keyword(s):  
Active Site ◽  
13C Labeling ◽  
Endor Spectroscopy ◽  
Femo Cofactor

scholarly journals DFT Study of Unstrained Ketone C-C Bond Activation via Rhodium(I)-Catalyzed Suzuki-Miyaura Cross-Coupling Reactions

2019 ◽  
Author(s):  
Dengmengfei Xiao ◽  
Lili Zhao ◽  
Diego Andrada
Keyword(s):  
Density Functional ◽  
Bond Activation ◽  
Chemical Reactivity ◽  
Cross Coupling ◽  
Underlying Mechanism ◽  
Reductive Elimination ◽  
Coupling Reactions ◽  
Co Catalysts ◽  
Cross Coupling Reactions ◽  
Strain Model

Unstrained cyclic ketones can participate in cooperative Suzuki-Miyaura cross-coupling type reaction using rhodium(I)-based catalyst via C-C bond activation. The regioselectivity indicates a trend where the most substituted side is activated and it is controlled by the beta-substituents. In this work, Density Functional Theory (DFT) calculations have been carried out to disclose the underlying mechanism in the reaction of a ketone series and arylboronate using ylidene as ancillary ligand and pyridine as co-catalysts. The computed energies suggest the reductive elimination step with the highest energy while the reductive elimination has the highest energy barrier. By the means of the Activation Strain Model (ASM) of chemical reactivity, it is found that the ketone strain energy released on the oxidative addition does not control the relativity of the OA reactivity, but indeed is the interaction energy between Rh(I) and C-C bond the ruling effect. The effect of the beta-substituents on regioselectivity has been additionally studied.

C≡C Triple Bond Activation by Heterocyclic Aluminum Phosphinides

2010 ◽  
Vol 29 (6) ◽  
pp. 1323-1330 ◽  
Author(s):  
Hauke Westenberg ◽  
J. Chris Slootweg ◽  
Alexander Hepp ◽  
Jutta Kösters ◽  
Steffi Roters ◽  
...  
Keyword(s):  
Triple Bond ◽  
Bond Activation

scholarly journals H2 Formation Holds the Key to Opening the Fe Coordination Sites of Nitrogenase FeMo-cofactor for Dinitrogen Activation

2020 ◽  
Author(s):  
Yong Li ◽  
Wan-Lu Li ◽  
Jin-Cheng Liu ◽  
Jun-Bo Lu ◽  
W. H. Eugen Schwarz ◽  
...  
Keyword(s):  
Double Bond ◽  
Binding Site ◽  
Energy Release ◽  
Triple Bond ◽  
Quantum Mechanical ◽  
Essential Step ◽  
Coordination Sites ◽  
Femo Cofactor ◽  
H2 Formation ◽  
Electron Transfers

The present quantum-mechanical and molecular-mechanics study reveals the crucial roles of H<sub>2</sub> formation, of H<sub>2</sub>S shift and of N<sub>2</sub> bond expansion in the nitrogenase process of the reduction of N<sub>2</sub> to <a href="https://en.wikipedia.org/wiki/Ammonia">NH<sub>3</sub></a>. Proton and electron transfers to the Fe(C@Fe<sub>6</sub>S<sub>9</sub>)Mo unit of the FeMo-co complex weaken the Fe-S and Fe-H bonds and expose the <b>Fe</b> coordination sites, coupled with energy release due to H<sub>2</sub> generation. Thereby the two sites <b>Fe2</b> and <b>Fe6</b> become prepared for stronger N<sub>2</sub> adsorption, expanding and attenuating the ǀN≡Nǀ bond. After subsequent detachment of H<sub>2</sub>S from its Fe binding site into a holding site of the rearranged protein residue, the <b>Fe6</b> site becomes completely unfolded, and the N<sub>2</sub> triple bond becomes completely activated to an ‑<u>N</u>=<u>N</u>- double bond for easy subsequent hydrogenation to NH<sub>3</sub>. We explain in particular, why the obligatory H<sub>2</sub> formation is an essential step in N<sub>2</sub> adsorption and activation

Stoichiometric and Catalytic (η 5-Cyclopentadienyl)cobalt-Mediated Cycloisomerizations of Ene-Yne-Ene Type Allyl Propargyl Ethers

Synthesis ◽  
2019 ◽  
Vol 52 (03) ◽  
pp. 399-416
Author(s):  
Chu-An Chang ◽  
Stefan Gürtzgen ◽  
Erik P. Johnson ◽  
K. Peter C. Vollhardt
Keyword(s):  
Double Bond ◽  
Oxidative Coupling ◽  
Triple Bond ◽  
Furan Ring ◽  
Reductive Elimination ◽  
Potential Utility ◽  
Deuterium Labeling ◽  
Terminal Double Bond ◽  
Hydride Elimination ◽  
Diene Complex

The complexes CpCoL2 (Cp = C5H5; L = CO or CH2=CH2) mediate the cycloisomerizations of α,δ,ω-enynenes containing allylic ether linkages to 3-(oxacyclopentyl or cycloalkyl)furans via the intermediacy of isolable CpCo-η 4-dienes. A suggested mechanism comprises initial complexation of the triple bond and one of the double bonds, then oxidative coupling to a cobalt-2-cyclopentene, terminal double bond insertion to assemble a cobalta-4-cycloheptene, β-hydride elimination, and reductive elimination to furnish a CpCo-η 4-diene. When possible, the cascade continues through cobalt-mediated hydride shifts and dissociation of the aromatic furan ring. The outcome of a deuterium labeling experiment supports this hypothesis. The reaction exhibits variable stereoselectivity with a preference for the trans-product (or, when arrested, its syn-Me CpCo-η 4-diene precursor), but is completely regioselective in cases in which the two alkyne substituents are differentiated electronically by the presence or absence of an embedded oxygen. Regioselectivity is also attained by steric discrimination or blocking one of the two possible β-hydride elimination pathways. When furan formation is obviated by such regiocontrol, the sequence terminates in a stable CpCo-η 4-diene complex. The conversion of the cyclohexane-fused substrate methylidene-2-[5-(2-propenyloxy)-3-pentynyl]cyclohexane into mainly 1-[(1R*,3aS*,7aS*)-7a-methyloctahydroinden-1-yl]-1-ethanone demonstrates the potential utility of the method in complex synthesis.

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