scholarly journals Catalytic activation of ethylene C-H bonds on uniform d8 Ir(I) and Ni(II) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts

2019 ◽  
Author(s):  
Nicholas R. Jaegers ◽  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Dan Klaus ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Molecular Level ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Catalytic Activation ◽  
Dehydrogenative Coupling ◽  
Ethylene Conversion ◽  
Active Metal ◽  
First Time

<div> <p>The homolytic activation of the strong C-H bonds in ethylene is demonstrated, for the first time, on d<sup>8</sup> Ir(I) and Ni(II) single atoms in the cationic positions of zeolites H-FAU and H-BEA under ambient conditions. The oxidative addition of C<sub>2</sub>H<sub>4</sub> to the metal center occurs with the formation of a d<sup>6</sup> metal vinyl hydride, explaining the initiation of the Cossee-Arlman cycle on d<sup>8</sup> M(I/II) sites in the absence of pre-existing M-H bonds. Under mild reaction conditions (80-220ᵒC, 1 bar), the catalytic dimerization to butenes and dehydrogenative coupling of ethylene to butadiene occurs over these catalysts. Butene-1 is not converted to butadiene under the reaction conditions applied. Post-reaction characterization of the two materials reveals that the active metal cations remain site-isolated whereas deactivation occurs due to the formation of carbonaceous deposits on the zeolites. Our findings have significant implications for the molecular level understanding of ethylene conversion and the development of new ways to functionalize C-H bonds under mild conditions.</p> </div>

scholarly journals Catalytic activation of ethylene C-H bonds on uniform d8 Ir(I) and Ni(II) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts

2019 ◽  
Author(s):  
Nicholas R. Jaegers ◽  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Dan Klaus ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Molecular Level ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Catalytic Activation ◽  
Dehydrogenative Coupling ◽  
Ethylene Conversion ◽  
Active Metal ◽  
First Time

<div> <p>The homolytic activation of the strong C-H bonds in ethylene is demonstrated, for the first time, on d<sup>8</sup> Ir(I) and Ni(II) single atoms in the cationic positions of zeolites H-FAU and H-BEA under ambient conditions. The oxidative addition of C<sub>2</sub>H<sub>4</sub> to the metal center occurs with the formation of a d<sup>6</sup> metal vinyl hydride, explaining the initiation of the Cossee-Arlman cycle on d<sup>8</sup> M(I/II) sites in the absence of pre-existing M-H bonds. Under mild reaction conditions (80-220ᵒC, 1 bar), the catalytic dimerization to butenes and dehydrogenative coupling of ethylene to butadiene occurs over these catalysts. Butene-1 is not converted to butadiene under the reaction conditions applied. Post-reaction characterization of the two materials reveals that the active metal cations remain site-isolated whereas deactivation occurs due to the formation of carbonaceous deposits on the zeolites. Our findings have significant implications for the molecular level understanding of ethylene conversion and the development of new ways to functionalize C-H bonds under mild conditions.</p> </div>

Activation of Ethylene C-H Bonds on Uniform D8 Ir(I) and Ni(II) Cations in Zeolites: Catalytic Butadiene and Butenes Production Under Mild Conditions

2019 ◽  
Author(s):  
Nicholas R. Jaegers ◽  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Dan Klaus ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Molecular Level ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Mild Conditions ◽  
Carbonaceous Deposits ◽  
Dehydrogenative Coupling ◽  
Ethylene Conversion ◽  
Active Metal ◽  
First Time

<div> <p>The homolytic activation of the strong C-H bonds in ethylene is demonstrated, for the first time, on d<sup>8</sup> Ir(I) and Ni(II) single atoms in the cationic positions of zeolites H-FAU and H-BEA under ambient conditions. The oxidative addition of C<sub>2</sub>H<sub>4</sub> to the metal center occurs with the formation of a Ir(III) and Ni(IV) vynil hydride, explaining the initiation of the Cossee-Arlman cycle on d<sup>8</sup> M(I/II) sites in the absence of pre-existing M-H bonds. Under mild reaction conditions (80-220ᵒC, 1 bar), the catalytic dimerization to butenes and the unprecedented dehydrogenative coupling of ethylene to butadiene occurs over these catalysts. Butene-1 is not converted to butadiene under the reaction conditions applied. Post-reaction characterization of the two materials reveals that the active metal cations remain site-isolated whereas deactivation occurs due to the formation of carbonaceous deposits on the zeolites. Our findings have significant implications for the molecular level understanding of ethylene conversion and the development of new ways to functionalize C-H bonds under mild conditions.</p> </div>

scholarly journals Review on the Impact of Polyols on the Properties of Bio-Based Polyesters

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2969
Author(s):  
Kening Lang ◽  
Regina J. Sánchez-Leija ◽  
Richard A. Gross ◽  
Robert J. Linhardt
Keyword(s):  
Tissue Engineering ◽  
Biomedical Applications ◽  
Molecular Level ◽  
Potential Utility ◽  
Reaction Conditions ◽  
Wide Range ◽  
Soft Tissue Engineering ◽  
The Impact ◽  
Optimal Reaction

Bio-based polyol polyesters are biodegradable elastomers having potential utility in soft tissue engineering. This class of polymers can serve a wide range of biomedical applications. Materials based on these polymers are inherently susceptible to degradation during the period of implantation. Factors that influence the physicochemical properties of polyol polyesters might be useful in achieving a balance between durability and biodegradability. The characterization of these polyol polyesters, together with recent comparative studies involving creative synthesis, mechanical testing, and degradation, have revealed many of their molecular-level differences. The impact of the polyol component on the properties of these bio-based polyesters and the optimal reaction conditions for their synthesis are only now beginning to be resolved. This review describes our current understanding of polyol polyester structural properties as well as a discussion of the more commonly used polyol monomers.

scholarly journals Synthesis, Structures, Electrochemistry, and Catalytic Activity towards Cyclohexanol Oxidation of Mono-, Di-, and Polynuclear Iron(III) Complexes with 3-Amino-2-Pyrazinecarboxylate

2020 ◽  
Vol 10 (8) ◽  
pp. 2692
Author(s):  
Anirban Karmakar ◽  
Luísa M.D.R.S. Martins ◽  
Yuliya Yahorava ◽  
M. Fátima C. Guedes da Silva ◽  
Armando J. L. Pombeiro
Keyword(s):  
Coordination Polymer ◽  
Heterogeneous Catalysts ◽  
Saturated Calomel Electrode ◽  
Two Dimensional ◽  
Reaction Conditions ◽  
Ability To Act ◽  
Tert Butyl Hydroperoxide ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the heteronuclear Fe(III)/Na(I) two-dimensional coordination polymer [Fe(N3)(μ-L)2(μ-O)1/2(Na)(μ-H2O)1/2]n (4), are reported. Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with iron(III) chloride under different reaction conditions were studied, and the obtained compounds were characterized by elemental analysis, Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray single-crystal diffraction. Compound 1 is a neutral mononuclear complex, whereas 2 is mono-anionic with its charge being neutralized by triethylammonium cation. Compounds 3 and 4 display a di-methoxido-bridged dinuclear complex and a two-dimensional heterometallic Fe(III)/Na(I) polynuclear coordination polymer, respectively. Compounds 3 and 4 are the first examples of methoxido- and oxido-bridged iron(III) complexes, respectively, with 3-amino-2-pyrazinecarboxylate ligands. The electrochemical study of these compounds reveals a facile single-electron reversible Fe(III)-to-Fe(II) reduction at a positive potential of 0.08V vs. saturated calomel electrode (SCE), which is in line with their ability to act as efficient oxidants and heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation (with tert-butyl hydroperoxide) of cyclohexanol to cyclohexanone (almost quantitative yields after 1 h). Moreover, the catalysts are easily recovered and reused for five consecutive cycles, maintaining a high activity and selectivity.

scholarly journals Catalytic activation of ethylene C–H bonds on uniform d8 Ir(i) and Ni(ii) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts

2019 ◽  
Vol 9 (23) ◽  
pp. 6570-6576 ◽  
Author(s):  
Nicholas R. Jaegers ◽  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Daniel W. Klas ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Metal Ions ◽  
Ethylene Polymerization ◽  
Heterogeneous Catalysts ◽  
Molecular Level ◽  
Catalytic Activation

The long-debated intermediates of ethylene polymerization are revealed using uniform d8 metal ions in zeolites.

Out with Acetonitrile: Water-assisted Accelerated-Aging Synthesis of CuI-Pyrazine Hybrid Materials

2021 ◽  
Author(s):  
Will Lucas ◽  
Feier Hou
Keyword(s):  
Hybrid Materials ◽  
Elevated Temperatures ◽  
Accelerated Aging ◽  
Synthetic Method ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Dry Grinding ◽  
Excess Amount ◽  
First Time ◽  
Two Hybrid

CuI and pyrazine form three hybrid materials, [(CuI)2(pyrazine)] (Yellow), [(CuI)2(pyrazine)2] (Orange), and [(CuI)(pyrazine)] (Red). In this work, Red was prepared using a green synthetic method, water-assisted accelerated-aging synthesis, for the first time. The syntheses were performed under ambient conditions with only water and no organic solvents. Depending on the reaction conditions, the other two hybrid materials can be formed as well: Orange was formed immediately after dry grinding CuI and pyrazine, while Yellow can be formed from Red and excess amount of CuI at mildly elevated temperatures. The impacts of temperature and types and amounts of liquid added to the aging mixture on the accelerated-aging synthesis were studied, and mechanisms of the synthesis and interconversions between the three CuI-pyrazine hybrid materials were proposed.

A Single Turnover (STO) Characterization of Supported Palladium Catalysts

1987 ◽  
Vol 111 ◽  
Author(s):  
Robert L. Augustine ◽  
David R. Baum
Keyword(s):  
Palladium Catalysts ◽  
Active Sites ◽  
Pt Catalyst ◽  
Catalyst Characterization ◽  
Pt Catalysts ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Pd Catalysts ◽  
Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

scholarly journals Cloning and characterization of a maize cytochrome-b5 reductase withFe3+-chelate reduction capability

1999 ◽  
Vol 338 (2) ◽  
pp. 499-505 ◽  
Author(s):  
Paolo BAGNARESI ◽  
Séverine THOIRON ◽  
Monique MANSION ◽  
Michel ROSSIGNOL ◽  
Paolo PUPILLO ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Molecular Level ◽  
Cytochrome B5 ◽  
Functional Assay ◽  
Sequence Information ◽  
Cytochrome B5 Reductase ◽  
Maize Roots ◽  
First Time ◽  
Translational Mechanisms

We previously purified an NADH-dependent Fe3+-chelate reductase (NFR) from maize roots with biochemical features of a cytochrome-b5 reductase (b5R) [Sparla, Bagnaresi, Scagliarini and Trost (1997) FEBS Lett. 414, 571–575]. We have now cloned a maize root cDNA that, on the basis of sequence information, calculated parameters and functional assay, codes for NFR. Maize NFR has 66% and 65% similarity to mammal and yeast b5R respectively. It has a deduced molecular mass of 31.17 kDa and a pI of 8.53. An uncharged region is observed at its N-terminus but no myristoylation consensus site is present. Taken together, these results, coupled with previous biochemical evidence, prove that NFR belongs to the b5R class and document b5R from a plant at the molecular level for the first time. We have also identified a putative Arabidopsis thaliana NFR gene. Its organization (nine exons) closely resembles mammalian b5Rs. Several NFR isoforms are expected to exist in maize. They are probably not produced by alternative translational mechanisms as occur in mammals, because of specific constraints observed in the maize NFR cDNA sequence. In contrast with yeast and mammals, tissue-specific and various subcellular localizations of maize b5R isoforms could result from differential expression of the various members of a multigene family. The first molecular characterization of a plant b5R indicates an overall remarkable evolutionary conservation for these versatile reductase systems. In addition, the well-characterized Fe3+-chelate reduction capabilities of NFR, in addition to known Fe3+-haemoglobin reduction roles for mammal b5R isoforms, suggest further and more generalized roles for the b5R class in endocellular iron reduction.

Synthesis and characterization of functional six-membered ring carbonates for the preparation of orthogonal couplers

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Thorsten Anders ◽  
Helmut Keul ◽  
Martin Möller
Keyword(s):  
Membered Ring ◽  
Surface Coatings ◽  
Dipolar Cycloaddition ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Ring Opening Reaction ◽  
Coupling Principle ◽  
Multifunctional Polymers ◽  
Nucleophilic Ring Opening

Abstract On the basis of commercially available trimethylolpropane (TMP) three six-membered ring carbonates were prepared, substituted with reactive side groups: a chloroformate (2a), an imidazolyl carbamate (2b) and a phenyl carbonate (2c). Their synthesis and characterizations are described and compared to known ring carbonates with reactive side groups. Starting from 2a-c orthogonal couplers 3a and 3b were synthesized for conversion under mild reaction conditions. In a model reaction 2-azidoethyl 2-N-acetylamino-2-deoxy- -D-glucopyranose and tertbutyl- N-(3-aminopropyl) carbamate were linked with coupler 3a via a 1,3-dipolar cycloaddition and a nucleophilic ring-opening reaction. This coupling principle can be used for the preparation of multifunctional polymers or surface coatings at ambient conditions.

scholarly journals Direct use of mineral fertilizers MAP, DAP, and TSP as heterogeneous catalysts in organic reactions

2016 ◽  
Vol 5 (6) ◽  
pp. 615-623 ◽  
Author(s):  
Imane Bahammou ◽  
Ayoub Esaady ◽  
Said Boukhris ◽  
Rachida Ghailane ◽  
Nouzha Habbadi ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Knoevenagel Condensation ◽  
Aromatic Aldehydes ◽  
Significant Loss ◽  
Mineral Fertilizers ◽  
Phosphate Fertilizers ◽  
Reaction Conditions ◽  
Catalytic Activities ◽  
First Time ◽  
Direct Use

In this paper, we reported the first use of phosphate fertilizers (MAP, DAP, and TSP) as heterogeneous catalysts for organic reactions.  Their catalytic activities were investigated in the first time in Knoevenagel condensation of various aromatic aldehydes with malononitrile at room temperature.  These minerals phosphate showed high catalytic activities and ability to be recovering and reusing without a significant loss in their catalytic activities.  In order to reach the optimal reaction conditions for Knoevenagel condensation, we carried out a kinetic study of the effect of reaction time, the effect of solvent, the amount of catalysts and the variation of the range of the particles size the more active.  The best conditions were obtained by the use of these fertilizers (MAP, DAP, and TSP) in their commercial status, simply crashed in powder, without any purification, using ethanol as solvent.  These phosphate fertilizers prove to be very promising and effective heterogeneous catalysts for the condensation of Knoevenagel.

Sign in / Sign up

Export Citation Format

Share Document