Search results for " chemistry"
showing 10 items of 41321 documents
Comparative hydroamination of aniline and substituted anilines with styrene on different zeolites, triflate based catalysts and their physical mixtur…
2014
Abstract Catalytic performances of different zeolites (Beta and mordenites), scandium triflate based catalysts, mesoporous UVM-7 encapsulated scandium triflate and physical mixtures prepared under ultrasound irradiation were evaluated in the hydroamination of aniline and substituted anilines with styrene. The performances of these catalysts were controlled by the type of acidity and strength. Thus, the conversion was mainly controlled by the strength of the acid sites and their accessibility, while the selectivity appeared to be controlled by the Lewis/Bronsted type of acidity. Lewis acid catalysts directed the reactions mainly to the formation of the Markovnikov adducts while Bronsted acid…
Hierarchical Beta zeolites obtained in concentrated reaction mixtures as catalysts in tetrahydropyranylation of alcohols
2020
Abstract Hierarchical zeolites consisting of Beta nanoparticles (15–40 nm) were obtained via hydrothermal treatment of a concentrated zeolite gel-precursor (H2O/Si = 2.5–14) without utilization of complex SDAs. The proposed approach is based on the formation of a large number of zeolite nuclei under particular crystallization conditions, followed by their agglomeration resulting in the dense packing of the particles preventing their further growth. The micelles of cetyltrimethylammonium bromide (CTAB) can be used to additionally limit the growth of zeolite nanoparticles during hydrothermal treatment of concentrated reaction mixtures. Such deceleration of crystallization promotes the formati…
Substitution of the laser borane anti-B18H22 with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron h…
2018
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive. Compound 3a is of unprecedented ten-vertex nido:eight-vertex arachno two-atoms-in-common architecture. The si…
On the Rationalization of Formation of Solvates: Experimental and Computational Study of Solid Forms of Several Nitrobenzoic Acid Derivatives
2020
Analysis of crystal structures, molecular properties, interaction strength in solution and computationally generated non-solvated form solid form landscapes of five chloronitrobenzoic acid isomers ...
Kinetic and Electrochemical Studies of the Oxidative Addition of Demanding Organic Halides to Pd(0): the Efficiency of Polyphosphane Ligands in Low P…
2013
International audience; Oxidative addition (OA) of organic halides to palladium(0) species is a fundamental reaction step which initiates the C–C bond formation catalytic processes typical of Pd(0)/Pd(II) chemistry. The use of structurally congested polyphosphane ligands in palladium-catalyzed C–C bond formation has generated very high turnover numbers (TONs) in topical reactions such as Heck, Suzuki, Sonogashira couplings, and direct sp2C–H functionalization. Herein, the OA of aryl bromides to Pd(0) complexes stabilized by ferrocenylpolyphosphane ligands L1 (tetraphosphane), L2 (triphosphane), and L3 (diphosphane) is considered. The investigation of kinetic constants for the addition of Ph…
Electrochemical Arylation Reaction
2018
Arylated products are found in various fields of chemistry and represent essential entities for many applications. Therefore, the formation of this structural feature represents a central issue of contemporary organic synthesis. By the action of electricity the necessity of leaving groups, metal catalysts, stoichiometric oxidizers, or reducing agents can be omitted in part or even completely. The replacement of conventional reagents by sustainable electricity not only will be environmentally benign but also allows significant short cuts in electrochemical synthesis. In addition, this methodology can be considered as inherently safe. The current survey is organized in cathodic and anodic con…
Highly Anisotropic Rhenium(IV) Complexes: New Examples of Mononuclear Single-Molecule Magnets
2013
The rhenium(IV) complex (NBu4)2[ReBr4(ox)] (1) (ox = oxalate and NBu4(+) = tetra-n-butylammonium cation) has been prepared and its crystal structure determined by X-ray diffraction. The structure is made up of discrete [ReBr4(ox)](2-) anions and bulky NBu4(+) cations. Each [ReBr4(ox)](2-) anion is surrounded by six NBu4(+) cations, which preclude any significant intermolecular contact between the anionic entities, the shortest rhenium···rhenium distance being 9.373(1) Å. Variable temperature dc and ac magnetic susceptibility measurements and field-dependent magnetization experiments on polycrystalline samples of 1 reveal the occurrence of highly anisotropic magnetically isolated Re(IV) cent…
A thermally/chemically robust and easily regenerable anilato-based ultramicroporous 3D MOF for CO 2 uptake and separation
2021
The combination of the properly designed novel organic linker, 3,6-N-ditriazoyil-2,5-dihydroxy-1,4-benzoquinone (trz2An), with CoII ions results in a 3D ultramicroporous MOF with high CO2 uptake capacity and separation efficiency, with particular attention to CO2/N2 and CO2/CH4 gas mixtures. This material consists of 1D chains of octahedrally coordinated CoII ions linked through the anilato ligands in the equatorial positions and to the triazole substituents from two neighbouring chains in the two axial positions. This leads to a 3D microporous structure with voids with an affinity for CO2 molecules and channels that enable the selective entrance of CO2 but not of molecules with larger kine…
Enantiomeric Resolution of Asymmetric-Carbon-Free Binuclear Double-Stranded Cobalt(III) Helicates and Their Application as Catalysts in Asymmetric Re…
2018
A series of double-stranded binuclear helicates [Co2(H1)2]4+, [Co2(H2)2]4+, and [Co2(H3)2]4+, derived from monodeprotonated bis-pyridyl hydrazine-based ligands of H21, H22, and H23 with one, two, and three -CH2 spacers, were obtained. These asymmetric-carbon-free racemic helicates were separated into their ΔΔ and ΛΛ enantiomers. The resolved helicates were examined for the first time as enantioselective catalysts in asymmetric benzoylation and nitroaldol reactions.
Viewpoint: Atomic-Scale Design Protocols toward Energy, Electronic, Catalysis, and Sensing Applications
2019
Nanostructured materials are essential building blocks for the fabrication of new devices for energy harvesting/storage, sensing, catalysis, magnetic, and optoelectronic applications. However, because of the increase of technological needs, it is essential to identify new functional materials and improve the properties of existing ones. The objective of this Viewpoint is to examine the state of the art of atomic-scale simulative and experimental protocols aimed to the design of novel functional nanostructured materials, and to present new perspectives in the relative fields. This is the result of the debates of Symposium I "Atomic-scale design protocols towards energy, electronic, catalysis…