Osmium-Mediated CH and CC Bond Cleavage of a Phenolic Substrate:p-Quinone Methide and Methylene Arenium Pincer Complexes

2007 ◽  
Vol 13 (5) ◽  
pp. 1382-1393 ◽  
Author(s):  
Régis M. Gauvin ◽  
Haim Rozenberg ◽  
Linda J. W. Shimon ◽  
Yehoshoa Ben-David ◽  
David Milstein
Keyword(s):  
Bond Cleavage ◽  
Quinone Methide ◽  
Pincer Complexes

B–H Bond Cleavage via Metal–Ligand Cooperation by Dearomatized Ruthenium Pincer Complexes

2014 ◽  
Vol 33 (14) ◽  
pp. 3716-3726 ◽  
Author(s):  
Aviel Anaby ◽  
Burkhard Butschke ◽  
Yehoshoa Ben-David ◽  
Linda J. W. Shimon ◽  
Gregory Leitus ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Pincer Complexes ◽  
Metal Ligand

Synthesis of a lignin polymer model consisting of only phenolic β-O-4 linkages and testing its reactivity under alkaline conditions 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Holzforschung ◽  
2009 ◽  
Vol 63 (6) ◽  
Author(s):  
Jackson D. Megiatto ◽  
Emmanuel Cazeils ◽  
Stéphane Grelier ◽  
Christian Gardrat ◽  
Frédérique Ham-Pichavant ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Bond Cleavage ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Quinone Methide ◽  
Scanning Calorimetry ◽  
Good Thermal Stability ◽  
Maldi Tof ◽  
Flight Mass Spectrometry ◽  
Alkaline Conditions

Abstract A trimeric β-O-4 lignin model bearing a styrene unit was polymerized in the presence of azobisisobutyronitrile as an initiator of free radical polymerization. The polymer analysis achieved by size exclusion chromatography (SEC), 1H, 13C, 31P NMR, matrix-assisted laser desorption ionization combined with time-of-flight mass spectrometry (MALDI-ToF MS), differential scanning calorimetry, and thermogravimetry indicated its well-defined structure with good thermal stability at temperatures usually applied for alkaline pulping. SEC analysis proved a high degree of polymerization despite the size of the phenolic β-O-4 units in the polymer structure. MALDI-ToF spectrometry indicated that the polymer is composed of phenolic β-O-4 elements only. The chemical reactivity under alkaline conditions of the polymer was studied by both HPLC and 31P NMR. These two methods revealed two main concurrent processes, which include an oxidation of the phenol part followed by Cα-Cβ bond cleavage, and a formation of a quinone methide followed by its β-O-4 bond cleavage.

C−N, C−S and S−S Bond Cleavage by Rhodium PC carbene P Pincer Complexes

2020 ◽  
Vol 15 (18) ◽  
pp. 2873-2878
Author(s):  
Hendrik Tinnermann ◽  
Rowan D. Young
Keyword(s):  
Bond Cleavage ◽  
Pincer Complexes

Arene C–H Bond Coordination versus C–H Bond Cleavage in Low-Valent Group 6 Carbonyl Pincer Complexes

2016 ◽  
Vol 35 (17) ◽  
pp. 3032-3039 ◽  
Author(s):  
Sara R. M. M. de Aguiar ◽  
Berthold Stöger ◽  
Ernst Pittenauer ◽  
Günter Allmaier ◽  
Luis F. Veiros ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Pincer Complexes ◽  
Group 6 ◽  
Low Valent

B−C Bond Cleavage of BArFAnion Upon Oxidation of Rhodium(I) with AgBArF. Phosphinite Rhodium(I), Rhodium(II), and Rhodium(III) Pincer Complexes

2008 ◽  
Vol 27 (10) ◽  
pp. 2293-2299 ◽  
Author(s):  
Hiyam Salem ◽  
Linda J. W. Shimon ◽  
Gregory Leitus ◽  
Lev Weiner ◽  
David Milstein
Keyword(s):  
Bond Cleavage ◽  
Pincer Complexes

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

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.

Room Temperature Alkali Metal Reduction of Carbon Dioxide

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 CO<sub>2</sub> to access useful CO<sub>2</sub>-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 CO<sub>2</sub> and the MGE. Herein we report the first successful chemical reduction of CO<sub>2</sub> at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO<sub>2</sub> adduct (<b>1</b>) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO<sub>2</sub>)]<sub>n</sub>(M = Li, Na, K, <b> 2</b>-<b>4</b>) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M<sub>2</sub>(CAAC–CO<sub>2</sub>)]<sub>n </sub>(<b>5</b>-<b>8</b>). It is notable that these crystalline clusters of reduced CO<sub>2</sub> may also be isolated via the “one-pot” reaction of free CO<sub>2</sub> 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 <b>2</b>-<b>8</b> were investigated using a combination of experimental and theoretical methods.<br>

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

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 O<sub>2</sub>. These processes are relevant to both O<sub>2</sub> reduction and O<sub>2</sub> evolution and the mechanism was probed in detail both experimentally and computationally.

Effect of Hydrated Metal Salts on the Coordination Product of Cobalt(II) halide and PNP Type Ligand, 2,6-bis(di-tertbutylphosphinomethyl) pyridine

2018 ◽  
Author(s):  
Tasneem Siddiquee ◽  
Abdul Goni
Keyword(s):  
Metal Salts ◽  
Molar Ratio ◽  
Pincer Complexes ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Pincer Ligand ◽  
Tetrahedral Geometry ◽  
X Ray ◽  
Distorted Tetrahedral Geometry ◽  
Cobalt Center

Chemical treatment of CoX<sub>2</sub><b><sup>. </sup></b>6H<sub>2</sub>O (X = Cl, Br, I) with the potentially tridentate PNP pincer ligand 2,6-bis(di-<i>tert</i>-butylphosphinomethyl)pyridine in 1:1 molar ratio results in cobalt(II) halide-PNP pincer complexes. The effect of the hydrated metal source on molecular structure and geometry of the complexes was studied by single crystal X-ray diffraction analysis. The complexes are neutral and the cobalt center adopts a penta-coordinate system with potential atropisomerization. Within the unit cell there are two distinct molecules per asymmetric unit. One of the two phosphorus atoms in the PNP ligand was observed to be partially oxidized to phosphinoxide. Disorder in the structure reflects a mixture of square pyramidal and distorted tetrahedral geometry.

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>

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