Search results for "Catalyst"
showing 10 items of 516 documents
Proximity Effect using a Nanocage Structure: Polyhedral Oligomeric Silsesquioxane-Imidazolium Tetrachloro- palladate Salt as a Precatalyst for the Su…
2016
A polyhedral oligomeric silsesquioxane-imidazolium tetrachloropalladate salt (POSS-Imi-PdCl4) was prepared by the reaction of a polyhedral oligomeric silsesquioxane-imidazolium chloride salt (POSS-Imi-Cl) with PdCl2 and used as a pre-catalyst for the Suzuki-Miyaura reaction in water at 100 °C at a low loading (0.08-0.16 mol %). Biphenyl compounds were isolated in high to excellent yields. A comparison of the POSS-based catalyst with the corresponding catalyst without the nanocage structure (i.e., 1-butyl-3-methylimidazolium tetrachloropalladate) highlighted the role of the POSS structure to reach higher yields in the Suzuki-Miyaura reaction. This result is ascribed to a proximity effect of …
Applications and stereoselective syntheses of P-chirogenic phosphorus compounds.
2016
International audience; Phosphorus compounds bearing chirality on the P-center are usually qualified as P-chirogenic or P-stereogenic. This chemical class concerns natural products, agrochemistry, molecular materials, biology and pharmacy, although it is certainly in coordination chemistry and in asymmetric catalysis using chiral transition metal complexes that P-chirogenic phosphorus compounds are the most used. The chiral phosphine ligands and their uses in asymmetric metal-catalyzed reactions have been widely reviewed in literature. However, an overview covering the applications as well as the stereoselective syntheses of all classes of phosphorus compounds has not yet been provided. Thi…
Studies of structural composition distribution heterogeneity in ethylene/1-hexene copolymers using thermal fractionation technique (SSA): Effect of c…
2005
Investigations into the compositional heterogeneity of ethylene/1-hexene copolymers obtained with various zirconocene/MAO catalysts, either homogeneous or supported on inorganic carriers such as a complex of magnesium chloride with tetrahydrofuran or methyl alcohol, were conducted. The dependence between metallocene structure, as well as catalyst immobilization, and the compositional heterogeneity of the related products was investigated. It was found that the heterogeneity of copolymers is determined by the metallocene catalyst structure. The amount of peaks on the DSC thermograms of copolymers and their division increase with the increase of bulkiness of the ligand in the catalytic system…
Increased conformational rigidity of humic substances by oxidative biomimetic catalysis
2005
A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed …
Electrocatalytic properties of manganese and cobalt polyporphine films toward oxygen reduction reaction
2018
International audience; Novel member of polymetalloporphines, namely manganese polymetalloporphine of type I (pMnP-I) obtained by ion exchange from magnesium polyporphine of type I (pMgP-I) is reported for the first time and compared to its cobalt analogue (pCoP-I). Both polymer films have been obtained via two-step procedure: demetaladon of the pMgP-I electrode film via its exposure to trifluoroacetic acid solution, resulting in formation of the metal-free polyporphine of type I (pH(2)P-I) followed by electrochemically induced incorporation of Co or Mn ions from the acetonitrile solution of cobalt and manganese perchlorates. A further oxidative transformation of pCoP-I, polymer films has l…
Struktura i właściwości kopolimerów etylenu z norbornenem otrzymanych wobec katalizatora wanadocenowego
2018
Kopolimery etylenu z norbornenem ze względu na swoje wyjątkowe właściwości pozwalają na ich potencjalnie szerokie zastosowanie. Jednak w zależności od warunków prowadzenia syntezy, a przede wszystkim od zastosowanego katalizatora, właściwości takiego kopolimeru mogą się zmieniać w szerokim zakresie. W prezentowanej pracy zbadano właściwości wybranych kopolimerów etylenu (E) z norbornenem (NB) otrzymanych przy wykorzystaniu homogenicznego katalizatora wanadocenowego Cp2VCl2 aktywowanego tradycyjnym związkiem glinoorganicznym AlEt2Cl. Określono zależność pomiędzy stopniem wbudowania komonomeru w łańcuch kopolimeru a mikrostrukturą, masą molową, rozkładem mas molowych, temperaturą zeszklenia i…
Application of Silsesquioxanes in the Preparation of Polyolefin-Based Materials
2023
This paper is a review of studies on the use of the polyhedral oligomeric silsesquioxanes (POSS) of various structures in the synthesis of polyolefins and the modification of their properties, namely: (1) components of organometallic catalytic systems for the polymerization of olefins, (2) comonomers in the copolymerization with ethylene, and (3) fillers in composites based on polyolefins. In addition, studies on the use of new silicon compounds, i.e., siloxane–silsesquioxane resins, as fillers for composites based on polyolefins are presented. The authors dedicate this paper to Professor Bogdan Marciniec on the occasion of his jubilee.
Wpływ wybranych parametrów na efektywność katalizowanej wanadocenem kopolimeryzacji etylenu z norbornenem i właściwości otrzymanych produktów
2019
W pracy zbadano wpływ parametrów reakcji na kopolimeryzację etylenu z norbornenem wobec katalizatora wanadocenowego (Cp2VCl2) w obecności trichloroctanu etylu (ETA). Przeprowadzono serię reakcji kopolimeryzacji, zmieniając w każdej z nich jeden z parametrów reakcji: temperaturę lub ciśnienie etylenu. Następnie zbadano temperaturę zeszklenia, stopień wbudowania norbornenu i mikrostrukturę otrzymanych kopolimerów, poddając je analizie DSC oraz spektroskopii 13C NMR. Wykazano wpływ badanych parametrów na aktywność katalizatora oraz ilość i sposób wbudowania jednostek norbornenu w łańcuch polimerowy, jak również wartość temperatury zeszklenia produktu. Stwierdzono, że właściwości otrzymanego ko…
Copolymerization of Ethylene with Selected Vinyl Monomers Catalyzed by Group 4 Metal and Vanadium Complexes with Multidentate Ligands: A Short Review
2021
This paper gives a short overview of homogeneous post-metallocene catalysts based on group 4 metal and vanadium complexes bearing multidentate ligands. It summarizes the catalytic behavior of those catalysts in copolymerization of ethylene with 1-olefins, with styrenic monomers and with α,ω-alkenols. The review is focused on finding correlations between the structure of a complex, its catalyst activity and comonomer incorporation ability, as well as the microstructure of the copolymer chains.
1-(1-Benzyl-2,5-dimethyl-4-phenyl-1H-pyrrol-3-yl)ethanone
2017
In the title compound, C21H21NO, the dihedral angles between the planes of the phenyl and pyrrole rings are 47.04 (5) and 79.27 (3)°. In the crystal, centrosymmetrically related molecules are linked into dimers by pairs of C—H...O hydrogen bonds, forming rings of graph-set motifR22(16).