scholarly journals Geometrically Constrained Cationic Low‐Coordinate Tetrylenes: Highly Lewis Acidic σ‐Donor Ligands in Catalytic Systems

2021 ◽  
Author(s):  
Terrance John Hadlington ◽  
Philip Maximillian Keil
Keyword(s):  
Donor Ligands ◽  
Catalytic Systems ◽  
Geometrically Constrained

Catalytic Activity of Binary and Triple Systems Based on Redox Inactive Metal Compound, LiSt and Additives of Monodentate Ligands-Modifiers: DMF, HMPA and PhOH, in Selective Ethylbenzene Oxidation with Dioxygen

2016 ◽  
Vol 10 (3) ◽  
pp. 259-270
Author(s):  
Ludmila Matienko ◽  
◽  
Larisa Mosolova ◽  
Vladimir Binyukov ◽  
Gennady Zaikov ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Triple System ◽  
Metal Compound ◽  
Ethylbenzene Oxidation ◽  
Catalytic Systems ◽  
Triple Systems ◽  
Lithium Compound ◽  
Mechanism Of Catalysis ◽  
Monodentate Ligands

Mechanism of catalysis with binary and triple catalytic systems based on redox inactive metal (lithium) compound {LiSt+L2} and {LiSt+L2+PhOH} (L2=DMF or HMPA), in the selective ethylbenzene oxidation by dioxygen into -phenylethyl hydroperoxide is researched. The results are compared with catalysis by nickel-lithium triple system {NiII(acac)2+LiSt+PhOH} in selective ethylbenzene oxidation to PEH. The role of H-bonding in mechanism of catalysis is discussed. The possibility of the stable supramolecular nanostructures formation on the basis of triple systems, {LiSt+L2+PhOH}, due to intermolecular H-bonds, is researched with the AFM method.

Dual-Function, Light Switchable Cobalt Catalysis via Active Site Metamorphosis

2019 ◽  
Author(s):  
Enrico Bergamaschi ◽  
Frédéric Beltran ◽  
Christopher Teskey
Keyword(s):  
Visible Light ◽  
Active Site ◽  
Catalytic Site ◽  
Dual Function ◽  
Catalytic Systems ◽  
Hydride Complex ◽  
Dual Functional ◽  
Multiple Processes ◽  
Olefin Migration

<p></p><p></p><p>Switchable catalysis offers opportunities to control the rate or selectivity of a reaction <i>via</i> a stimulus such as pH or light. However, few examples of switchable catalytic systems that can facilitate multiple processes exist. Here we report a rare example of such dual-functional, switchable catalysis. Featuring an easily prepared, bench-stable cobalt(I) hydride complex in conjunction with pinacolborane, we can completely alter the reaction outcome between two widely employed transformations – olefin migration and hydroboration – with visible light as the sole trigger. This dichotomy arises from ligand photodissociation which leads to metamorphosis of the active catalytic site, resulting in divergent mechanistic pathways.</p><p></p><p></p>

Host-Guest Interactions on Electrode Surfaces for Immobilization of Molecular Catalysts

2020 ◽  
Author(s):  
Laurent Sévery ◽  
Jacek Szczerbiński ◽  
Mert Taskin ◽  
Isik Tuncay ◽  
Fernanda Brandalise Nunes ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Heterogeneous Systems ◽  
Catalytic Systems ◽  
New Approach ◽  
Molecular Systems ◽  
Electrode Surfaces ◽  
Catalytic Surfaces ◽  
Oxide Electrodes ◽  
The Stability ◽  
Molecular Catalysts

The strategy of anchoring molecular catalysts on electrode surfaces combines the high selectivity and activity of molecular systems with the practicality of heterogeneous systems. The stability of molecular catalysts is, however, far less than that of traditional heterogeneous electrocatalysts, and therefore a method to easily replace anchored molecular catalysts that have degraded could make such electrosynthetic systems more attractive. Here, we apply a non-covalent “click” chemistry approach to reversibly bind molecular electrocatalysts to electrode surfaces via host-guest complexation with surface-anchored cyclodextrins. The host-guest interaction is remarkably strong and allows the flow of electrons between the electrode and the guest catalyst. Electrosynthesis in both organic and aqueous media was demonstrated on metal oxide electrodes, with stability on the order of hours. The catalytic surfaces can be recycled by controlled release of the guest from the host cavities and readsorption of fresh guest. This strategy represents a new approach to practical molecular-based catalytic systems.

Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

2018 ◽  
Author(s):  
Katherine Marczenko ◽  
James Goettel ◽  
Gary Schrobilgen
Keyword(s):  
Room Temperature ◽  
Triphenylphosphine Oxide ◽  
Donor Ligands ◽  
Mechanical Shock ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Coordination ◽  
Xenon Trioxide ◽  
Distorted Octahedra ◽  
Coordination Spheres

Oxygen coordination to the Xe(VI) atom of XeO<sub>3</sub> was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO<sub>3</sub>, which detonates when mechanically or thermally shocked, the solid [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub>, [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub>,<sub> </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3 </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> are air-stable whereas [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> slowly decomposes over several days and [(CH<sub>3</sub>)<sub>2</sub>CO]<sub>3</sub>XeO<sub>3</sub> undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub> is a distorted square pyramid which provides the first example of a five-coordinate XeO<sub>3</sub> adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO<sub>3</sub>. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.

Nickel-Catalyzed Inter- and Intramolecular Carbon-Sulfur Bond Metathesis by Reversible Arylation

2019 ◽  
Author(s):  
Tristan Delcaillau ◽  
Alessandro Bismuto ◽  
Zhong Lian ◽  
Bill Morandi
Keyword(s):  
Good Yield ◽  
Functional Group ◽  
Product Formation ◽  
Single Bond ◽  
Ring Closing Metathesis ◽  
Catalytic Systems ◽  
Metathesis Reactions ◽  
New Applications ◽  
Further Development ◽  
Sulfur Bond

A nickel-catalyzed carbon-sulfur bond metathesis has been developed to access high-value thioethers. 1,2-bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional group tolerant reaction. Further, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring-closing metathesis which does not involve alkene bonds. In-depth organometallic studies support a reversible Ni(0)-Ni(II) pathway to product formation. Overall, this work does not only disclose a more sustainable and more functional group tolerant alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information which are highly relevant to the further development and application of unusual single bond metathesis reactions.

Palladium Promoted Copolymerization of Carbon Monoxide with Polar or Nonpolar Olefinic Monomers

2020 ◽  
Vol 24 ◽  
Author(s):  
Yanlin Zong ◽  
Qiankun Li ◽  
Hongliang Mu ◽  
Zhongbao Jian
Keyword(s):  
Carbon Monoxide ◽  
Physical Properties ◽  
Vinyl Monomers ◽  
Pd Catalysts ◽  
Catalytic Systems

Abstract:: The copolymers of carbon monoxide (CO) and olefins, namely polyketones, are a family of widely used materi-als. In the catalytic preparation of these materials, palladium(II) catalysts represent the most successful catalytic systems. The production of both alternating and non-alternating polyketones has been achieved, with great difference in their physical properties. Herein, a variety of palladium(II) catalysts employed for the copolymerization of CO with various olefinic mon-omers such as ethylene, α-olefins, styrene and polar vinyl monomers are fully summarized. The influence of important fac-tors such as solvents and counterions on specific copolymerization, is also discussed. This review aims to enlighten the de-sign of new Pd catalysts with improved properties, as well as the development of new polyketone materials.

Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

2020 ◽  
Vol 23 ◽  
Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Sol Gel ◽  
Reaction Times ◽  
Significant Loss ◽  
Spectral Studies ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Solvent Free Conditions ◽  
Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

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