Ni-, Pd-, or Pt-catalyzed ethylene dimerization: a mechanistic description of the catalytic cycle and the active species

2010 ◽  
Vol 8 (5) ◽  
pp. 1040 ◽  
Author(s):  
Dipankar Roy ◽  
Raghavan B. Sunoj
Keyword(s):  
Active Species ◽  
Catalytic Cycle ◽  
Ethylene Dimerization ◽  
Pt Catalyzed

Mechanism of N-heterocyclic carbene-catalyzed chemical fixation of CO2 with aziridines: a theoretical study

RSC Advances ◽  
2014 ◽  
Vol 4 (33) ◽  
pp. 17236-17244 ◽  
Author(s):  
Weiyi Li ◽  
Dongfeng Huang ◽  
Yajing Lv
Keyword(s):  
Theoretical Study ◽  
Active Species ◽  
Catalytic Cycle ◽  
Catalyst Precursor ◽  
Chemical Fixation

Free NHC is a catalyst precursor, while the carboxylate intermediate is the active species in the catalytic cycle.

scholarly journals Solution X-Ray Absorption Spectroscopy (XAS) for Analysis of Catalytically Active Species in Reactions with Ethylene by Homogeneous (Imido)vanadium(V) Complexes—Al Cocatalyst Systems

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1016 ◽  
Author(s):  
Kotohiro Nomura
Keyword(s):  
Active Species ◽  
Oxidation States ◽  
Donor Ligands ◽  
Ethylene Dimerization ◽  
Edge Structure ◽  
Donor Ligand ◽  
X Ray ◽  
Catalytically Active ◽  
Type V ◽  
X Ray Absorption

Solution V K-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) analysis of vanadium(V) complexes containing both imido ligands and anionic ancillary donor ligands (L) of type, V(NR)(L)X2 (R = Ar, Ad (1-adamantyl); Ar = 2,6-Me2C6H3; X = Cl, Me, L = 2-(ArNCH2)C5H4N, OAr, WCA-NHC, and 2-(2’-benzimidazolyl)pyridine; WCA-NHC = anionic NHCs containing weak coordinating B(C6F5)3), which catalyze ethylene dimerization and/or polymerization in the presence of Al cocatalysts, has been explored. Different catalytically actives species with different oxidation states were formed depending upon the Al cocatalyst (MAO, Me2AlCl, AliBu3, etc.) and the anionic ancillary donor ligand employed. The method is useful for obtainment of the direct information of the active species (oxidation state, basic framework around the centered metal) in solution, and for better understanding in catalysis mechanism and organometallic as well as coordination chemistry.

scholarly journals Reduction of Nitrobenzene to Aniline by CO/H2O in the Presence of Palladium Nanoparticles

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 404 ◽  
Author(s):  
Agnieszka Krogul-Sobczak ◽  
Jakub Cedrowski ◽  
Patrycja Kasperska ◽  
Grzegorz Litwinienko
Keyword(s):  
Catalytic Activity ◽  
Palladium Nanoparticles ◽  
Metallic Nanoparticles ◽  
Active Species ◽  
Catalytic Cycle ◽  
Heterocyclic Ligands ◽  
Aromatic Nitrocompounds ◽  
First Time ◽  
Transient Intermediate

The transformation of aromatic nitrocompounds into amines by CO/H2O is catalyzed by palladium(II) complexes. Recently, we have proposed that the catalytic cycle includes Pd0 as the transient intermediate and herein, for the first time, we describe the application of palladium nanoparticles (PdNPs) stabilized by monodentate N-heterocyclic ligands as nanocatalysts facilitating the reduction of Ar–NO2 into Ar–NH2 by CO/H2O. Among the series—Pd(II) complexes, PdNPs and commercial Pdblack—the highest catalytic activity was observed for PdNPs (3.0 ± 0.5 nm) stabilized by 4-Me-pyridine in the presence of 2-Cl-pyridine. The results may be helpful for mechanistic considerations on the role of metallic nanoparticles as active species in other organic processes.

scholarly journals Pd Nanoparticles and Mixture of CO2/CO/O2 Applied in the Carbonylation of Aniline

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 877 ◽  
Author(s):  
Dominik Madej ◽  
Adrian Konopko ◽  
Piotr Piotrowski ◽  
Agnieszka Krogul-Sobczak
Keyword(s):  
Reaction Time ◽  
Palladium Nanoparticles ◽  
High Stability ◽  
Pd Nanoparticles ◽  
Active Species ◽  
Catalytic Cycle ◽  
Aliphatic Amines ◽  
Pyridine Ligand ◽  
Reaction Conditions ◽  
Derivatives Of

CO2 is a compound of high stability which proves useful in some organic syntheses as a solvent or component decreasing explosivity of gases. It is also a good carbonylating agent for aliphatic amines although not for aromatic ones, the latter being carbonylated with phosgene or, as in our previous works, with CO/O2 in the presence of Pd(II) complexes. In this work we have used the mixture of CO/O2 and CO2 for carbonylation of aniline to N,N’-diphenylurea. After optimization of the reaction conditions (56% of CO2 in CO2/CO mixture) we studied the activity of three kinds of pre-catalysts: (a) Pd(II) complexes, (b) Pdblack, and (c) palladium nanoparticles (PdNPs) in the presence of derivatives of pyridine (XnPy). The highest conversion of aniline (with selectivity towards N,N-diphenylurea ca. 90%) was observed for PdNPs. The results show that catalytic cycle involves Pd(0) stabilized by pyridine ligand as active species. Basing on this observation, we put the hypothesis that application of PdNPs instead of Pd(II) complex can efficiently reduce the reaction time.

Isolation and Crystal Structure of the Proposed Low-Valent Active Species in the H2Activation Catalytic Cycle

2013 ◽  
Vol 2013 (22-23) ◽  
pp. 3978-3986 ◽  
Author(s):  
Daisuke Inoki ◽  
Takahiro Matsumoto ◽  
Hidetaka Nakai ◽  
Seiji Ogo
Keyword(s):  
Crystal Structure ◽  
Active Species ◽  
Catalytic Cycle ◽  
Low Valent

scholarly journals Density Functional Theory Study into the Reaction Mechanism of Isonitrile Biosynthesis by the Nonheme Iron Enzyme ScoE

2021 ◽  
Author(s):  
Hafiz Saqib Ali ◽  
Sidra Ghafoor ◽  
Sam P. de Visser
Keyword(s):  
Reaction Mechanism ◽  
Hydrogen Atom ◽  
Proton Transfer ◽  
Active Site ◽  
Density Functional ◽  
Active Species ◽  
Nonheme Iron ◽  
Catalytic Cycle ◽  
Hydrogen Atom Abstraction ◽  
Catalytic Cycles

AbstractThe nonheme iron enzyme ScoE catalyzes the biosynthesis of an isonitrile substituent in a peptide chain. To understand details of the reaction mechanism we created a large active site cluster model of 212 atoms that contains substrate, the active oxidant and the first- and second-coordination sphere of the protein and solvent. Several possible reaction mechanisms were tested and it is shown that isonitrile can only be formed through two consecutive catalytic cycles that both use one molecule of dioxygen and α-ketoglutarate. In both cycles the active species is an iron(IV)-oxo species that in the first reaction cycle reacts through two consecutive hydrogen atom abstraction steps: first from the N–H group and thereafter from the C–H group to desaturate the NH-CH2 bond. The alternative ordering of hydrogen atom abstraction steps was also tested but found to be higher in energy. Moreover, the electronic configurations along that pathway implicate an initial hydride transfer followed by proton transfer. We highlight an active site Lys residue that is shown to donate charge in the transition states and influences the relative barrier heights and bifurcation pathways. A second catalytic cycle of the reaction of iron(IV)-oxo with desaturated substrate starts with hydrogen atom abstraction followed by decarboxylation to give isonitrile directly. The catalytic cycle is completed with a proton transfer to iron(II)-hydroxo to generate the iron(II)-water resting state. The work is compared with experimental observation and previous computational studies on this system and put in a larger perspective of nonheme iron chemistry.

Neuartige basische Liganden für die homogenkatalytische Methanolcarbonylierung, XI [1]. Ether-Phosphan-Cobalt-Komplexe in der katalytischen Methanolhydrocarbonylierung zu Acetaldehyd / Novel Basic Ligands for the H om ogeneous Catalytic Methanol Carbonylation, XI [1]. Ether Phosphane Cobalt Complexes in the Catalytic Hydrocarbonylation of Methanol to Acetaldehyde

1987 ◽  
Vol 42 (12) ◽  
pp. 1527-1536 ◽  
Author(s):  
Ekkehard Lindner ◽  
Uwe Schober ◽  
Erhard Glaser ◽  
Hubert Norz ◽  
Peter Wegner
Keyword(s):  
Cobalt Complexes ◽  
Active Species ◽  
Catalytic Cycle ◽  
Simple Method ◽  
Model Complexes ◽  
Methanol Carbonylation ◽  
Catalytically Active ◽  
Trapping Reactions

AbstractPhP(CH2C4H7O2)2 (1) and [-CH2(Ph)P~D]2 (3a-c) [D = CH2C4H702 (a), CH2C4H7O (b). CH2CH2OCH3 (c)] are obtained by reaction of Li2PPh and Na(Ph)P~D with ClCH2C4H7O2 and C1CH2CH2Cl, respectively. 1 and 3a, b give rise to high selectivities and conversions in the cobalt catalyzed hydrocarbonylation of methanol to acetaldehyde. Model complexes of cobalt which are of importance in the catalytic cycle are synthesized. Complexes of the type X2Co(Ph2P~D)2 (6az, 6bx-bz, 6cx-cz), especially those with X = I, obtained from CoX2 [X = Cl (x), Br (y), I (z)] and the ether phosphanes Ph2P~D (5a-c), are regarded as precursors of the catalytically active species. With K[HB(sec-C4H9)3] they are reduced to the cobalt(I) complexes XCo(Ph2P~D)(Ph2P~D) (7az, 7bx-bz, 7cx-cz). Trapping reactions with CO, PPh3 or 5b, c lead to the compounds XCo(CO)2(Ph2P~D)2 (8az, 8bx-bz, 8cx-cz), XCoPPh3(Ph2P~D)2 (9bx-bz). and XCo(Ph2P~D)3 (10bz, cz), respectively, with cleavage of a Co-O bond. The reduction of X2Co(PPh3)2 (11x, z) with K[HB(sec-C4H9)3] represents a simple method for the preparation of the complexes XCo(CO)2(PPh3)2 (13x, z) which are formed from the intermediates XCo(PPh3)2 · THF (12x, z) in the presence of CO.

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