Ammonia Formation Catalyzed by Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions

2021 ◽  
Author(s):  
Yoshiaki Nishibayashi ◽  
Fanqiang Meng ◽  
Shogo Kuriyama ◽  
Hiromasa Tanaka ◽  
Akihito Egi ◽  
...  
Keyword(s):  
Pincer Ligands ◽  
Reaction Conditions ◽  
Ammonia Formation

scholarly journals Ammonia Formation Catalyzed by Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions

2021 ◽  
Author(s):  
Yoshiaki Nishibayashi ◽  
Fanqiang Meng ◽  
Shogo Kuriyama ◽  
Hiromasa Tanaka ◽  
Akihito Egi ◽  
...  
Keyword(s):  
Pincer Ligands ◽  
Reaction Conditions ◽  
Ammonia Formation

scholarly journals Ammonia Formation Catalyzed by Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions

2020 ◽  
Author(s):  
Fanqiang Meng ◽  
Shogo Kuriyama ◽  
Hiromasa Tanaka ◽  
Akihito Egi ◽  
Kazunari Yoshizawa ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pincer Ligands ◽  
Pincer Ligand ◽  
Reaction Conditions ◽  
Rhenium Atom ◽  
Phosphine Complexes ◽  
Proton Source ◽  
Dinitrogen Complexes ◽  
Dinitrogen Complex ◽  
Ammonia Formation

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia in the reaction with KC<sub>8</sub> as a reductant and [HPCy<sub>3</sub>]BAr<sup>F</sup><sub>4</sub> (Cy = cyclohexyl, Ar<sup>F</sup> = 3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) as a proton source at –78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC<sub>8</sub> as a reductant and Me<sub>3</sub>SiCl as a silylating reagent under ambient reaction conditions to afford 11.3 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions by using rhenium-dinitrogen complexes as catalysts.

scholarly journals Ammonia Formation Catalyzed by Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions

2020 ◽  
Author(s):  
Fanqiang Meng ◽  
Shogo Kuriyama ◽  
Hiromasa Tanaka ◽  
Akihito Egi ◽  
Kazunari Yoshizawa ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pincer Ligands ◽  
Pincer Ligand ◽  
Reaction Conditions ◽  
Rhenium Atom ◽  
Phosphine Complexes ◽  
Proton Source ◽  
Dinitrogen Complexes ◽  
Dinitrogen Complex ◽  
Ammonia Formation

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia in the reaction with KC<sub>8</sub> as a reductant and [HPCy<sub>3</sub>]BAr<sup>F</sup><sub>4</sub> (Cy = cyclohexyl, Ar<sup>F</sup> = 3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) as a proton source at –78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC<sub>8</sub> as a reductant and Me<sub>3</sub>SiCl as a silylating reagent under ambient reaction conditions to afford 11.3 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions by using rhenium-dinitrogen complexes as catalysts.

Effect of substituents on molybdenum triiodide complexes bearing PNP-type pincer ligands toward catalytic nitrogen fixation

2019 ◽  
Vol 48 (10) ◽  
pp. 3182-3186 ◽  
Author(s):  
Takayuki Itabashi ◽  
Ikki Mori ◽  
Kazuya Arashiba ◽  
Aya Eizawa ◽  
Kazunari Nakajima ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pincer Ligands ◽  
Ammonia Production ◽  
Reaction Conditions ◽  
Effect Of Substituents

Molybdenum triiodide complexes bearing phenyl and ferrocenyl substituted PNP-type pincer ligands acted as more effective catalysts toward ammonia production under ambient reaction conditions.

Flexible Coordination of Carbodiphosphorane-based Pincer Ligands in Chromium(0) Carbonyl Complexes

2020 ◽  
Author(s):  
Leon Maser ◽  
Philipp Korzeniowski ◽  
Robert Langer
Keyword(s):  
Quantum Chemical ◽  
Tridentate Ligand ◽  
Pincer Ligands ◽  
Carbonyl Complexes ◽  
Neutral Complex ◽  
Reaction Conditions ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Stretching Vibration ◽  
The Stability

A series of chromium(0) complexes was obtained by subsequent irradiation of [Cr(CO)6] in the presence of [(Ph2P-CH2-PPh2)CH]+. Depending on the reaction conditions and the duration of irradiation, it is possible to isolate complexes with different coordination modes of the potentially tridentate ligand. Initially, the coordination of the terminal PPh2-groups is observed in [(κ2P,P’-{Ph2P-CH2-PPh2}CH)Cr(CO)4]+ (2), followed by the formation of fac- and mer-[(κ3P,C,P’-{Ph2P-CH2-PPh2}CH)Cr(CO)3]+ (3). In the presence of base the neutral complex [(κ3P,C,P’-{Ph2P-CH2-PPh2}C)Cr(CO)3] (4) can be isolated, for which the net donor strength of the central CDP-group is compared by the C-O-stretching vibration. Finally, the utilization of reductants like potassium graphite leads the loss of hydrogen and generation of an anionic chromium(0) complex (5). Using quantum chemical methods the stability of possible isomers is explored.

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

Dimensionally-Controlled Hydrothermal Tm3+-doped Oxidic Nanocrystals and Their Photoluminescence Properties

2010 ◽  
Vol 1247 ◽  
Author(s):  
Rocío Calderón-Villajos ◽  
Carlos Zaldo ◽  
Concepción Cascales
Keyword(s):  
Single Crystals ◽  
Fluorescence Lifetimes ◽  
Photoluminescence Properties ◽  
Reaction Conditions ◽  
Hydrothermal Processes ◽  
Bulk Single Crystals ◽  
Template Free ◽  
Reaction Media

AbstractControlled reaction conditions in simple, template-free hydrothermal processes yield Tm-Lu2O3 and Tm-GdVO4 nanocrystals with well-defined specific morphologies and sizes. In both oxide families, nanocrystals prepared at pH 7 reaction media exhibit photoluminescence in ∼1.95 μm similar to bulk single crystals. For the lowest Tm3+ concentration (0.2 % mol) in GdVO4 measured 3H4 and 3F4 fluorescence lifetimes τ are very near to τrad.

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  
Keyword(s):  
Natural Products ◽  
Hydrogen Atom ◽  
Transition Metal ◽  
Hydrogen Atom Transfer ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Hydride Hydrogen ◽  
Sulfur Heterocycles ◽  
One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

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