Search results for "Homogeneous catalysi"

Silver-Catalyzed C-C Bond Formation between Methane and Ethyl Diazoacetate in Supercritical CO2

2011

Even in the context of hydrocarbons’ general resistance to selective functionalization, methane’s volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH4) with ethyl diazoacetate (N2CHCO2Et) to yield ethyl propionate (CH3CH2CO2Et). The use of supercritical carbon dioxide (scCO2) as the solvent is key to the reaction’s success. Although the catalyst is only sparingly soluble in CH4/CO2 mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.

Inside a Shell—Organometallic Catalysis Inside Encapsulin Nanoreactors

2021

Abstract Compartmentalization of chemical reactions inside cells are a fundamental requirement for life. Encapsulins are self‐assembling protein‐based nanocompartments from the prokaryotic repertoire that present a highly attractive platform for intracellular compartmentalization of chemical reactions by design. Using single‐molecule Förster resonance energy transfer and 3D‐MINFLUX analysis, we analyze fluorescently labeled encapsulins on a single‐molecule basis. Furthermore, by equipping these capsules with a synthetic ruthenium catalyst via covalent attachment to a non‐native host protein, we are able to perform in vitro catalysis and go on to show that engineered encapsulins can be used …

Cyclodextrines confinantes : synthèse, propriétés complexantes et utilisation en catalyse asymétrique

2014

This manuscript is concerned with the design of novel catalytic systems derived from metallocyclodextrins. The first part describes new ways of functionalising the cyclodextrin primary face regioselectively for accessing inherently chiral P,P’ chelators. These heterodentate ligands gavequantitatively cis-chelate complexes with various d8 cations. Their rhodium(I) complexes were assessed in the asymmetric hydrogenation and hydroformylation of prochiral olefins. Thecoordination and catalytic properties of two phosphines derived from a- and b-cyclodextrin are also reported. With their phosphorus lone pair pointing toward the CD core, these confining ligands force the coordinated metal centre t…

Homogeneous Metal-Based Catalysis in Supercritical Carbon Dioxide as Reaction Medium

2016

Above 31.1 degrees C and 73.8 bar, carbon dioxide reaches the supercritical state, being transformed into a fluid (scCO(2)) that has attracted interest in the last few decades as reaction medium for several transition-metal-catalyzed organic transformations. The main feature of this fluid rests on its capability to dissolve large amounts of other gases such as hydrogen, carbon monoxide, ethylene, or even methane and light alkanes. In this manner, very high concentrations of these reactants are available for catalysis. In this contribution a review of the main achievements of the use of transition-metal complexes as catalysts in scCO(2) is presented.

Palladium‐Catalyzed C2−H Arylation of Unprotected (N−H)‐Indoles “On Water” Using Primary Diamantyl Phosphine Oxides as a Class of Primary Phosphine O…

2018

Book Review: Applied Homogeneous Catalysis with Organometallic Compounds. Vols. 1–3. 2nd. Edition. Edited by Boy Cornils and Wolfgang A. Herrmann

2002

Copolymerization of ethene with styrene using different methylalumoxane activated half-sandwich complexes

1997

Ethene was copolymerized with styrene using five different methylalumoxane (MAO) activated half-sandwich complexes of the general formula Me 2 Si(Cp)(N-R)MCl 2 , varying the substituents on the cyclopentadienyl ring and the substituent on the amide (Cp = tetramethylcyclopentadiene CBT, 1-indenyl IBT, 3-trimethylsilyl-1-indenyl SIBT, or fluorenyl FBZ, R = tert-butyl (complexes CBT,IBT, SIBT, FBZ ) or benzyl CAT), as well as the metal center ( M = Ti, except FBZ: M = Zr). Polymerization behavior was analyzed with respect to catalyst activity and polymerization kinetics, styrene incorporation, copolymer microstructure, and molecular weight. All complexes produced random poly(ethene-co-styrene)…

Copolymerization of ethylene with 1‐hexene over metallocene catalyst supported on complex of magnesium chloride with tetrahydrofuran

2004

The study of ethylene/1-hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp 2 ZrCl 2 )/methylaluminoxane (MAO), anchored on a MgCl 2 (THF) 2 support was carried out. The influence of 1-hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethylaluminum (AlMe 3 ), or diethylaluminum chloride (Et 2 AlCl)] on the behavior of the MgCl 2 (THF) 2 /Cp 2 ZrCl/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp 2 ZrC…

Organic Monolayers by B(C6F5)3-Catalyzed Siloxanation of Oxidized Silicon Surfaces

2017

Inspired by the homogeneous catalyst tris(pentafluorophenyl) borane [B(C6F5)3], which acts as a promotor of Si-H bond activation, we developed and studied a method of modifying silicon oxide surfaces using hydrosilanes with B(C6F5)3 as the catalyst. This dedihydrosiloxanation reaction yields complete surface coverage within 10 min at room temperature. Organic monolayers derived from hydrosilanes with varying carbon chain lengths (C8-C18) were prepared on oxidized Si(111) surfaces, and the thermal and hydrolytic stabilities of the obtained monolayers were investigated in acidic (pH 3) medium, basic (pH 11) medium, phosphate-buffered saline (PBS), and deionized water (neutral conditions) for …

Thiazolium-based catalysts for the etherification reaction of benzylic alcohols under solvent-free condition

2015

Thiazolium and imidazolium hybrid materials were prepared by radical reactions between a mercaptopropyl-modified SBA-15 mesoporous silica and bis-vinylthiazolium or bis-vinylimidazolium dibromide salts. These hybrid materials were characterized by several techniques and were employed in the etherification reaction of 1-phenylethanol. Solvent-free conditions at 160C under different gas phases (oxygen, air, nitrogen and argon) were used. The thiazolium-based material displayed excellent performances. Further studies were carried out using unsupported thiazolium salts, with or without a methyl group at the C-2 position of the thiazolium moiety. These studies allowed us to propose a reaction me…