C-S Bond Cleavage of Allyl Thioethers by Zerovalent Ru Complexes

Jose Giner Planas; Masafumi Hirano; Sanshiro Komiya

doi:10.1246/cl.1998.123

Unusual rearrangement of modified PNP ligand based Ru complexes relevant to alcohol dehydrogenation catalysis

Chemical Communications ◽

10.1039/c9cc06024c ◽

2019 ◽

Vol 55 (76) ◽

pp. 11350-11353 ◽

Cited By ~ 2

Author(s):

Shubham Deolka ◽

Naziha Tarannam ◽

Robert R. Fayzullin ◽

Sebastian Kozuch ◽

Eugene Khaskin

Keyword(s):

Transition State ◽

Bond Cleavage ◽

Unusual Rearrangement ◽

Ru Complexes ◽

Alcohol Dehydrogenation

Hangman PNP pincer Ru complexes undergo an unusual sp2–sp3 C–C bond cleavage and formation via a spyrocyclopropane transition state.

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Unusual Rearrangement of Modified PNP Ligand based Ru Complexes Relevant to Alcohol Dehydrogenation Catalysis

10.26434/chemrxiv.8156741.v1 ◽

2019 ◽

Author(s):

Shubham Deolka ◽

Naziha Tarannam ◽

robert fayzullin ◽

sebastian kozuch ◽

Eugene Khaskin

Keyword(s):

Bond Cleavage ◽

Pincer Ligands ◽

Formation Processes ◽

Mechanistic Studies ◽

Unusual Rearrangement ◽

Isomerization Process ◽

Ru Complexes ◽

Alcohol Dehydrogenation

We report the synthesis of ‘hangman-type’ PNP pincer ligands and their associated Ru complexes. Upon deprotonation, the complexes undergo sp2-sp3 C-C bond cleavage and subsequent C-C formation processes to form a new, one carbon unit longer backbone motif. Unlike the starting geometry, the products are completely inactive in alcohol dehydrogenation catalysis. DFT and mechanistic studies suggest an intramolecular isomerization process via a spyrocycle cyclopropane intermediate, dependent upon arm pyridine coordination and ligand sterics.

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Unusual Rearrangement of Modified PNP Ligand based Ru Complexes Relevant to Alcohol Dehydrogenation Catalysis

10.26434/chemrxiv.8156741 ◽

2019 ◽

Author(s):

Shubham Deolka ◽

Naziha Tarannam ◽

robert fayzullin ◽

sebastian kozuch ◽

Eugene Khaskin

Keyword(s):

Bond Cleavage ◽

Pincer Ligands ◽

Formation Processes ◽

Mechanistic Studies ◽

Unusual Rearrangement ◽

Isomerization Process ◽

Ru Complexes ◽

Alcohol Dehydrogenation

We report the synthesis of ‘hangman-type’ PNP pincer ligands and their associated Ru complexes. Upon deprotonation, the complexes undergo sp2-sp3 C-C bond cleavage and subsequent C-C formation processes to form a new, one carbon unit longer backbone motif. Unlike the starting geometry, the products are completely inactive in alcohol dehydrogenation catalysis. DFT and mechanistic studies suggest an intramolecular isomerization process via a spyrocycle cyclopropane intermediate, dependent upon arm pyridine coordination and ligand sterics.

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Metal-Metal Cooperative Bond Activation by Heterobimetallic Alkyl, Aryl, and Acetylide PtII/CuI Complexes

10.26434/chemrxiv.11742687 ◽

2020 ◽

Author(s):

Shubham Deolka ◽

Orestes Rivada Wheelaghan ◽

Sandra Aristizábal ◽

Robert Fayzullin ◽

Shrinwantu Pal ◽

...

Keyword(s):

Alkyl Group ◽

Bond Activation ◽

Bond Cleavage ◽

Terminal Alkyne ◽

Alkyl Aryl ◽

Metal Metal ◽

The Stability ◽

Selective Formation ◽

Organoplatinum Compounds

We report selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from electron-deficient tetraarylborate [B(ArF)4]- anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the role of Cu center acts as a binding site for alkyne substrate, while activating its terminal C-H bond.

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Room Temperature Alkali Metal Reduction of Carbon Dioxide

10.26434/chemrxiv.12665336 ◽

2020 ◽

Author(s):

Lucas A. Freeman ◽

Akachukwu D. Obi ◽

Haleigh R. Machost ◽

Andrew Molino ◽

Asa W. Nichols ◽

...

Keyword(s):

Alkali Metal ◽

Alkali Metals ◽

Room Temperature ◽

Chemical Reduction ◽

Bond Cleavage ◽

Open Shell ◽

Metal Reduction ◽

One Pot ◽

Earth Abundant ◽

Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO2 to access useful CO2-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO2 and the MGE. Herein we report the first successful chemical reduction of CO2 at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO2 adduct (1) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO2)]n(M = Li, Na, K, 2-4) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M2(CAAC–CO2)]n (5-8). It is notable that these crystalline clusters of reduced CO2 may also be isolated via the “one-pot” reaction of free CO2 with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products 2-8 were investigated using a combination of experimental and theoretical methods.

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Oxygen-Oxygen Bond Cleavage and Formation in Co(II) Mediated Stoichiometric O2 Reduction via the Potential Intermediacy of a Co(IV) Oxyl Radical

10.26434/chemrxiv.7176392 ◽

2018 ◽

Author(s):

Lucie Nurdin ◽

Denis M. Spasyuk ◽

Laura Fairburn ◽

Warren Piers ◽

Laurent Maron

Keyword(s):

Bond Cleavage ◽

Peroxo Complex ◽

Oxygen Oxygen ◽

O2 Reduction ◽

Oxygen Bond ◽

Pentadentate Ligand

Diprotonation of a remarkably stable, toluene soluble cobalt peroxo complex supported by a neutral, dianionic pentadentate ligand leads to facile O-O bond cleavage and production of a highly reactive Co(IV) oxyl cation intermediate that dimerizes and releases O2. These processes are relevant to both O2 reduction and O2 evolution and the mechanism was probed in detail both experimentally and computationally.

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Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

10.26434/chemrxiv.7763657.v1 ◽

2019 ◽

Author(s):

Katsutoshi Sato ◽

Shin-ichiro Miyahara ◽

Yuta Ogura ◽

Kotoko Tsujimaru ◽

Yuichiro Wada ◽

...

Keyword(s):

Ammonia Synthesis ◽

Bond Cleavage ◽

Synthesis Process ◽

Strong Electron ◽

Mild Conditions ◽

Ru Nanoparticles ◽

Rate Determining Step ◽

Highly Active ◽

Composite Oxides ◽

Low Crystalline

To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeOx pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba2+, Ce3+ and La3+, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.

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Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

10.26434/chemrxiv.7763657 ◽

2019 ◽

Author(s):

Katsutoshi Sato ◽

Shin-ichiro Miyahara ◽

Yuta Ogura ◽

Kotoko Tsujimaru ◽

Yuichiro Wada ◽

...

Keyword(s):

Ammonia Synthesis ◽

Bond Cleavage ◽

Synthesis Process ◽

Strong Electron ◽

Mild Conditions ◽

Ru Nanoparticles ◽

Rate Determining Step ◽

Highly Active ◽

Composite Oxides ◽

Low Crystalline

To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeOx pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba2+, Ce3+ and La3+, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.

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Mechanisms of ATP to cAMP Conversion Catalyzed by the Mammalian Adenylyl Cyclase: A Role of Magnesium Coordination Shells and Proton Wires

10.26434/chemrxiv.9209180 ◽

2019 ◽

Author(s):

Bella Grigorenko ◽

Igor Polyakov ◽

Alexander Nemukhin

Keyword(s):

Adenylyl Cyclase ◽

Bond Cleavage ◽

Cyclic Adenosine Monophosphate ◽

Adenosine Monophosphate ◽

Md Simulations ◽

Coordination Shell ◽

Energy Profile ◽

One Step ◽

Type V

We report a mechanism of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) conversion by the mammalian type V adenylyl cyclase revealed in molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) simulations. We characterize a set of computationally derived enzyme-substrate (ES) structures showing an important role of coordination shells of magnesium ions in the solvent accessible active site. Several stable six-fold coordination shells of MgA2+ are observed in MD simulations of ES complexes. In the lowest energy ES conformation, the coordination shell of MgA2+ does not include the Oδ1 atom of the conserved Asp440 residue. Starting from this conformation, a one-step reaction mechanism is characterized which includes proton transfer from the ribose O3'H3' group in ATP to Asp440 via a shuttling water molecule and PA-O3A bond cleavage and O3'-PA bond formation. The energy profile of this route is consistent with the observed reaction kinetics. In a higher energy ES conformation, MgA2+ is bound to the Oδ1(Asp440) atom as suggested in the relevant crystal structure of the protein with a substrate analog. The computed energy profile initiated by this ES is characterized by higher energy expenses to complete the reaction. Consistently with experimental data, we show that the Asp440Ala mutant of the enzyme should exhibit a reduced but retained activity. All considered reaction pathways include proton wires from the O3'H3' group via shuttling water molecules.

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Ruthenium(II) Complexes Bearing Thioether-Appended α- Iminopyridine Ligands: Arene Precursors Permit Access to K2-N,N and K3-N,N,S Complexes

10.26434/chemrxiv.9693506.v1 ◽

2019 ◽

Author(s):

Victoria A. Ternes ◽

Hannah A. Morgan ◽

Austin P. Lanquist ◽

Michael P. Murray ◽

Bradley Wile

Keyword(s):

Crystal Structure ◽

Solid State ◽

Strong Field ◽

Active Role ◽

Binding Mode ◽

Phenethyl Alcohol ◽

Ru Complexes

Herein we report the preparation of a series of Ru(II) complexes featuring alpha-iminopyridine ligands bearing thioether functionality (NNSR, where R = Me, CH2Ph, Ph). Metallation using (p cymene)RuCl dimer permits access to (k2-N,N)Ru complexes in which the thioether moiety remains uncoordinated. In the presence of a strong field ligand such as acetonitrile or triphenylphosphine, the p-cymene moiety is displaced, and the ligand adopts a k3-N,N,S binding mode. These complexes are characterized using a combination of solution and solid state methods, including the crystal structure of [(NNSMe)Ru(NCMe)2Cl]Cl. The k2-N,N Ru(II) complexes are shown to serve as efficient precatalysts for the oxidation of sec-phenethyl alcohol at 5 mol% loadings, using a variety of external oxidants and solvents. The complex bearing an S-Ph donor was found to be the most active of those surveyed, suggesting that the thioether donor plays an active role in catalyst speciation for this transformation.

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