Search results for "Reactivity"
showing 10 items of 880 documents
Dual application of (aqua)(chlorido)(porphyrinato)chromium(III) as hypersensitive amine-triggered ON switch and for dioxygen activation.
2014
Although synthesis and substitution reactions of chlorido chromium(III) porphyrins Cr(III)(TPP)(Cl)(L) (H2TPP = 5,10,15,20-tetraphenyl porphyrin, L = pyridine, H2O, ROH, etc.), have been well-established in coordination chemistry for decades, an unexpected dichotomous reactivity of Cr(III)(TPP)(Cl)(H2O) (1) toward amines is disclosed here. This reactivity leads to the application of 1 as highly sensitive substoichiometric and irreversible ON switch for amine detection by an autocatalytic pathway. The concomitant activation of O2 by the 1/amine system is furthermore exploited in an electrochemically driven epoxidation of norbonene using O2 as initial oxidant.
Trapping Rare and Elusive Phosphinidene Chalcogenides
2017
Four-membered rings with a P2Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N-heterocyclic carbene, resulting in a base-stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3-dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2Ch2 rings can liberate phosphinidene chalcogenides. peerReviewed
Metallocene sulfide chemistry of niobium and tantalum: new insights into the formation of niobium-polysulfido complexes and synthesis, structure, and…
1992
The previously described reaction of Cp'2NbH3 (Cp' = t-BuC5H4) with S8 was investigated with regard to the kinetic stabilization of as yet elusive intermediates during the formation of the polysulfide complex Cp'4Nb2S9 (1). Therefore, the permethylated complex Cp*2NbS3H (2; Cp* = C5Me5) and the Ta complex Cp'2TaS2H (3) were synthesized in a related reaction and structurally investigated. Despite the problematic localization of the hydride atom during X-ray crystallographic studies, the molecules can be described in a proper manner: Characteristic of 2 and 3 are M(eta(2)-S2) cores to which either an SH (2) or a H (3) ligand is attached. Complex 3 is the first known tantalocene sulfide. It re…
Reaktion von elektronenreichen Heterocyclen mit Orthocarbonsäure-Derivaten, 12. Formylierung von Vinylindolen mit Diethoxycarbenium-tetrafluoroborat
1988
Reactions of Electron-Rich Heterocycles with Orthocarboxylic Acid Derivatives, 12. – Formylation of Vinylindoles with Diethoxycarbenium Tetrafluoroborate 2- and 3-vinylindoles 1, 3 are formylated with diethoxycarbenium tetrafluoroborate regioselectively. The significant selectivity and reactivity of formylation of diethoxycarbenium ion in comparison with other thermodynamically more stable dialkoxycarbenium ions are compatible with the known results of hetaryl functionalisation with orthocarboxylic acid derivatives.
Thermal properties of e-beam cured epoxy/thermoplastic matrices for advanced composite materials
2007
The aim of this work is to investigate the possibility to improve the thermal behaviour of epoxy based systems, cured by ionizing radiation, in order to produce matrices for advanced carbon fibres composites. Blends of two epoxy monomers, difunctional and trifunctional, have been polymerized by e-beam irradiation and the dynamic mechanical thermal properties have been investigated. The increase of the concentration of the trifunctional epoxy monomer in the blend causes a marked increase of the Tg, but strongly decreases the reactivity. Subsequently, blends of the same epoxy monomers with a high Tg thermoplastic toughening agent have been considered and their reactivity and the thermal prope…
The role of the trifluoromethyl group in reactivity and selectivity in polar cycloaddition reactions. A DFT study
2012
Abstract The role of the trifluoromethyl group in reactivity, regio-, and stereoselectivity in cycloaddition reactions has been analyzed by studying the 1,3-dipolar cycloaddition (13DC) reactions of nitrone 4 with 3,3,3-trifluoro-1-nitropropene 7b and 3,3,3-trifluoro-2-nitropropene 14 using density functional theory (DFT) methods at the B3LYP/6-311G(d) level. The recent M06-2X functional has also been evaluated but, although the thermodynamic performance is improved, the kinetic data are not necessarily better than those obtained by the popular B3LYP functional for cycloaddition reactions. Four reactive channels associated with the meta and ortho regio- and endo and exo stereoselective appr…
Oxo and Hydroxo Tantalocene Complexes: Synthesis and Reactivity. X-ray Molecular Structures of [(η5-Cp*)TaCl(OH)(η5-C5H4SiMe3)]+Cl-, (η5-Cp*)TaCl(O)…
2005
Exposure of a THF solution of tantalocene dichloride complexes (η 5 -Cp*)TaCl 2 (η 5 -C 5 H 4 -SiMe 3 ) (1) and (η 5 -Cp*)TaCl 2 (η 5 -C 5 H 5 ) (2) to the ambient atmosphere for 12 h leads to the formation of new tantalum(V) cationic hydroxo complexes [(η 5 -Cp*)TaCl(OH)(η 5 -C 5 H 4 SiMe 3 )] + -Cl- (3) and [(η 5 -Cp*)TaCl(OH)(η 5 -C 5 H 5 )]+Cl - (4). This oxidation reaction is more rapid under oxygen atmosphere since the hydroxo complexes are obtained in better yields within only 15 min. The hydroxo complexes are easily deprotonated by base to generate oxo complexes 5 and 6, which, in turn, react with trimethylsilyl triflate, giving the corresponding cationic silylated complexes 7 and 8…
Functionalization of Bambusurils by a Thiol-Ene Click Reaction and a Facile Method for the Preparation of Anion-Free Bambus[6]urils
2018
Sulfide-functionalized bambus[4]urils ((RS)8 BU[4]) and bambus[6]urils ((RS)12 BU[6]) were synthesized through thiol-ene click coupling reactions (TEC) of allylbambus[n]urils. Thiosugars were grafted to BU[4] and BU[6]. Synthesis of BU[6] derivatives always requires the use of a template anion (iodide, chloride, or bromide), which is enclosed in the cavity of BU[6]. We show that this anion influences the reactivity of bambus[6]urils. An encapsulated iodide makes allyl functions of allyl12 BU[6] less reactive towards TEC and hydrogenation reactions in comparison to the corresponding chloride or bromide inclusion complexes. This is critical for the chemical reactivity of BU[6] and even more t…
TI: Cyclophosphazenes as polymer modifiers
2003
The utilization of cyclophosphazenes as polymer modifiers is reviewed, with particular concern to their exploitation as versatile chain extenders, possibly for recycle problems, crosslinkers, to enhance mechanical properties of polymeric materials, branchers, to selectively introduce ramifications in linear polymers, and compatibilizers, to favor the formation of blends between originally incompatible organic macromolecules. The great versatility of the synthetic methods put forward for these substrates, together with the ease of controlling their modification, functionalization and reactivity are important parameters for the evaluation of which type of use is more feasible for these trimer…
Umsetzungen an polymeren
1968
Umsetzungen an Polymeren konnen mit verschiedenen Zielen ausgefuhrt werden: Darstellung neuer Polymerer oder Modifizierung der Eigenschaften bekannter Polymerer; Strukturaufklarung und Analytik bei Polymeren; Untersuchung chemischer Bestandigkeit und Alterungsprozesse; Einfuhrung spezifischer funktioneller Gruppen und Untersuchung ihrer Reaktivitat; Reaktionskinetik bei Polymeren. Folgende Themen werden an ausgewahlten Beispielen behandelt: Ringschlusreaktionen bei Polymeren; Ringoffnungsreaktionen bei Polymeren; Polymere mit metallorganischen Seitengruppen; Polymere mit ungepaarten Elektronen in den Seitengruppen; photochemische Reaktionen mit Polymeren. There are different aims for studyi…