Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction.

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

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

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

<p>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/LaCeO<i><sub>x</sub></i> 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 Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, 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.</p>

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

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

<p>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/LaCeO<i><sub>x</sub></i> 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 Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, 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.</p>

scholarly journals Palladium-Catalysed C–F Alumination of Fluorobenzenes: Mechanistic Diversity and Origin of Selectivity

2020 ◽  
Author(s):  
Feriel Rekhroukh ◽  
Wenyi Chen ◽  
Ryan Brown ◽  
Andrew J. P. White ◽  
Mark Crimmin
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Oxidative Addition ◽  
Fluorine Content ◽  
Model Potential ◽  
Heterometallic Complex ◽  
Experimental Support ◽  
Highly Active ◽  
Reaction Proceeds ◽  
Directing Group

A palladium pre-catalyst, [Pd(PCy<sub>3</sub>)<sub>2</sub>] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)<sub>2</sub>CH}Al] (<b>1</b>, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp<sup>2</sup> C–F bonds to sp<sup>2</sup> C–Al bonds and provides a route into reactive organoaluminium complexes (<b>2a-h</b>) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 ºC (and at appreciable rates at even –50 ºC) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs C–H) and high regioselectivities ( >90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy<sub>3</sub>)(<b>1</b>)<sub>2</sub>] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(<b>1</b>)<sub>2</sub>] and leads directly to the product. Pathway 2 involves a stepwise C–H to C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, allowing it to act as a directing group for the adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)<sub>2</sub>CH}AlH<sub>2</sub>] (<b>3</b>, Mes = 2,4,6-trimethylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

scholarly journals Palladium-Catalysed C–F Alumination of Fluorobenzenes: Mechanistic Diversity and Origin of Selectivity

2020 ◽  
Author(s):  
Feriel Rekhroukh ◽  
Wenyi Chen ◽  
Ryan Brown ◽  
Andrew J. P. White ◽  
Mark Crimmin
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Oxidative Addition ◽  
Fluorine Content ◽  
Model Potential ◽  
Heterometallic Complex ◽  
Experimental Support ◽  
Highly Active ◽  
Reaction Proceeds ◽  
Directing Group

A palladium pre-catalyst, [Pd(PCy<sub>3</sub>)<sub>2</sub>] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)<sub>2</sub>CH}Al] (<b>1</b>, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp<sup>2</sup> C–F bonds to sp<sup>2</sup> C–Al bonds and provides a route into reactive organoaluminium complexes (<b>2a-h</b>) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 ºC (and at appreciable rates at even –50 ºC) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs C–H) and high regioselectivities ( >90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy<sub>3</sub>)(<b>1</b>)<sub>2</sub>] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(<b>1</b>)<sub>2</sub>] and leads directly to the product. Pathway 2 involves a stepwise C–H to C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, allowing it to act as a directing group for the adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)<sub>2</sub>CH}AlH<sub>2</sub>] (<b>3</b>, Mes = 2,4,6-trimethylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

δ-MnO2 with an ultrahigh Mn4+ fraction is highly active and stable for catalytic wet air oxidation of phenol under mild conditions

2017 ◽  
Vol 7 (15) ◽  
pp. 3200-3204 ◽  
Author(s):  
Changjian Ma ◽  
Yaoyao Wen ◽  
Chengli Rong ◽  
Nuowei Zhang ◽  
Jinbao Zheng ◽  
...  
Keyword(s):  
Low Temperature ◽  
High Activity ◽  
The Self ◽  
Catalytic Wet Air Oxidation ◽  
Air Oxidation ◽  
Wet Air Oxidation ◽  
Mild Conditions ◽  
Highly Active ◽  
Oxidation Of Phenol ◽  
Very Low Temperature

The self-reactivated δ-MnO2 catalyst was developed, and showed high activity and stability for the CWAO of phenol at a very low temperature.

DFT modelling of a diphosphane − N-heterocyclic carbene–Rh(i) pincer complex rearrangement: a computational evaluation of the electronic effects in C–P bond activation

2018 ◽  
Vol 47 (8) ◽  
pp. 2662-2669 ◽  
Author(s):  
H.-L. Qin ◽  
J. Leng ◽  
W. Zhang ◽  
E. A. B. Kantchev
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Electronic Effects ◽  
Complex Rearrangement ◽  
Rate Determining Step ◽  
Computational Evaluation ◽  
Pincer Complex ◽  
Dft Modelling

DFT calculations confirmed that the rearrangement of a PCP-Rh-H pincer to a CCP-Rh-phosphane pincer occured by C–P oxidative addition (ΔG‡ = 29.5 kcal mol−1, rate-determining step), followed by P–H reductive elimination (ΔG‡ = 4.8 kcal mol−1).

Gas Cell Infrared and Attenuated Total Reflection Infrared Spectroscopic Studies for Organic–Inorganic Interactions in Adsorption of Fulvic Acid on the Goethite Surface Generating Carbon Dioxide

2021 ◽  
pp. 000370282199121
Author(s):  
Yuki Nakaya ◽  
Satoru Nakashima ◽  
Takahiro Otsuka
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Fulvic Acid ◽  
Spectroscopic Studies ◽  
Reaction Model ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Gas Cell ◽  
Rate Determining Step ◽  
Ir Spectroscopic

The generation of carbon dioxide (CO2) from Nordic fulvic acid (FA) solution in the presence of goethite (α-FeOOH) was observed in FA–goethite interaction experiments at 25–80 ℃. CO2 generation processes observed by gas cell infrared (IR) spectroscopy indicated two steps: the zeroth order slower CO2 generation from FA solution commonly occurring in the heating experiments of the FA in the presence and absence of goethite (activation energy: 16–19 kJ mol–1), and the first order faster CO2 generation from FA solution with goethite (activation energy: 14 kJ mol–1). This CO2 generation from FA is possibly related to redox reactions between FA and goethite. In situ attenuated total reflection infrared (ATR-IR) spectroscopic measurements indicated rapid increases with time in IR bands due to COOH and COO– of FA on the goethite surface. These are considered to be due to adsorption of FA on the goethite surface possibly driven by electrostatic attraction between the positively charged goethite surface and negatively charged deprotonated carboxylates (COO–) in FA. Changes in concentration of the FA adsorbed on the goethite surface were well reproduced by the second order reaction model giving an activation energy around 13 kJ mol–1. This process was faster than the CO2 generation and was not its rate-determining step. The CO2 generation from FA solution with goethite is faster than the experimental thermal decoloration of stable structures of Nordic FA in our previous report possibly due to partial degradations of redox-sensitive labile structures in FA.

scholarly journals Pd/Ni-Catalyzed Germa-Suzuki coupling via dual Ge–F bond activation

2021 ◽  
Author(s):  
Hajime Kameo ◽  
Akihiro Mushiake ◽  
Tomohito Isasa ◽  
Hiroyuki Matsuzaka ◽  
Didier Bourissou
Keyword(s):  
Bond Activation ◽  
Suzuki Coupling ◽  
Mild Conditions ◽  
Dual Activation

Pd/Ni → Ge–F interactions supported by phosphine-chelation were found to trigger dual activation of Ge–F bonds under mild conditions.

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