Cleavage and polymerization with the same catalyst: The catalyst system named in title, which cleaves polyethylene polypropylene under a hydrogen atmosphere, is also capable of polymerizing ethylene or propylene. This shows close relationship between olefin insertion β-alkyl elimination [Eq. (a), (P)=polymer chain(P)].

The catalytic cleavage under hydrogen of the C-H and C-C bonds alkanes with conventional catalysts requires high temperatures. Room-temperature hydrogenolysis simple is possible on a well-defined well-characterized zirconium hydride supported silica obtained by surface organometallic chemistry. structure resulting from (≡SiO)Zr(Np) 3 (Np, neopentyl) was determined extended x-ray absorption fine (EXAFS) 1 H 29 Si solid-state nuclear magnetic resonance infrared (IR) spectra. A mechanism for...

Catalytic materials bearing multiple sulfonic acid functional groups and positioned at varying distances from one another on the surface of mesoporous solids are prepared to explore effects that spatial arrangement active sites have catalytic activity selectivity. A series organosiloxane precursors containing either disulfide or sulfonate ester functionalities (synthons eventual groups) synthesized. From these molecular precursors, a variety organic-inorganic hybrid, mesostructured SBA-15...

Three azaphosphatranes were used as organocatalysts for the synthesis of cyclic carbonates from CO2 and epoxides. They proved to be efficient single-component, metal-free catalysts reaction simple or activated epoxides (styrene oxide, epichlorohydrin, glycidyl methyl ether) with under mild conditions, displaying high stability productivity over several days reaction. Substitution patterns on catalyst shown affect activity stability. Kinetic analysis allowed investigation mechanism.

The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, alumina surfaces have been carried out careful identification the resulting surface organometallic complexes in order to probe relationship between catalyst structure polymerization activity. characterization supported has achieved most cases by situ infrared spectroscopy, microanalysis, qualitative quantitative analysis evolved gases during labeled surface, solid state (1)H...

It is shown that the introduction of sterically demanding ligands in lanthanoid metal complexes can depend more on precise composition precursor than size new ligand. Thus, tris(r-butyl)methanol (“rmojt-H”) does not react with amides Ln[N(SiMe 3 ) 2 ] “late” (small) metals. However, fast and clean reactions occur less derivatives Ln[N(SiHMe , homoleptic Ln(tritox) (Ln = Y, Nd) being formed practically all metals this group elements. The molecular crystal structures some alkoxides are described.

Heterogeneous palladium catalysts ([Pd(NH3)4]2+/NaY and [Pd]/SBA-15) were applied to the synthesis of 2-functionalised indoles, giving generally high conversions selectivities (>89% yield) using only 1 mol % [Pd]-catalyst under standard reaction conditions (polar solvent, 80 °C). For 2,3-functionalised indoles by cross-coupling arylation, [Pd]/SBA-15 catalyst was found be particularly interesting, producing expected compound with =35% yield after 12 days reaction, which is comparable...

Ordered mesoporous silicas functionalized with alkylsulfonic acid and thiol group pairs have been shown to catalyze the synthesis of bisphenols from condensation phenol various ketones, activity selectivity highly dependent on distance between thiol. Here, a new route thiol/sulfonic paired catalysts is reported. A bis-silane precursor molecule containing both disulfide sulfonate ester bond grafted onto surface ordered silica, SBA-15, followed by simultaneous reduction hydrolysis. The...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSurface Organometallic Chemistry of Inorganic Oxides: The Synthesis and Characterization (.tplbond.SiO)Ta(:CHC(CH3)3)(CH2C(CH3)3)2 (.tplbond.SiO)2Ta(:CHC(CH3)3)(CH2C(CH3)3)Veronique Dufaud, Gerald P. Niccolai, Jean Thivolle-Cazat, Jean-Marie BassetCite this: J. Am. Chem. Soc. 1995, 117, 15, 4288–4294Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April...

Abstract The Suzuki–Miyaura reactions using mesoporous‐supported aryldicyclohexylphosphine as ligand have been investigated. catalysts were based on SBA‐15 type mesoporous silica which was transformed in a four‐step synthesis leading to phosphine‐containing hybrid material most productive catalytic system studied generated situ from this and the homogeneous palladium complex, Pd(OAc) 2 . Other systems for comparison [homogeneous cataysts, “preformed” catalyst obtained by reaction of PdCl...

The synthesis and characterization of heterogeneous catalysts containing surfaces functionalized with discrete pairs sulfonic acid thiol groups are reported. A catalyst having separated by three carbon atoms is ca. 3 times more active than a material randomly distributed in the condensation acetone phenol to bisphenol 14 cyclohexanone Z. Increasing acid/thiol distance paired materials decreases both activity selectivity. This work clearly reveals importance nanoscale organization two...

Combining tetraalkyl-ammonium halides and cavitand hosts as catalysts, we achieved the carboxylation of styrene oxide to produce cyclic carbonate from CO2 in good excellent yields. In a first approach presence chloride/tetraphosphonate catalytic systems, an enhanced activity reaction was observed depending on host–guest association. second set experiments, using tetramethylammonium halide/tetraphosphonate complexes obtained corresponding high yields, whereas used alone, salts are inactive...

The endohedral functionalization of a molecular cage by an azaphosphatrane unit has allowed for the creation highly engineered catalytic cavities efficient conversion CO2 into cyclic carbonates. Strong structure/activity/stability correlations have been demonstrated careful adjustment size, shape, and electronic properties hemicryptophane host.

Non-heme iron, vanadium, and copper complexes bearing hemicryptophane cavities were evaluated in the oxidation of methane water by hydrogen peroxide. According to 1H nuclear magnetic resonance studies, a hydrophobic cage accommodates molecule proximity oxidizing site, leading an improvement efficiency selectivity for CH3OH CH3OOH compared those analogous devoid cage. While showed low catalytic efficiency, their vanadium iron counterparts exhibited higher turnover numbers, ≤13.2 ≤9.2,...

Porous ionic liquids simultaneously absorb carbon dioxide and catalyse its reaction with epoxides to form cyclic carbonates under mild conditions.

Participation of the oxygen atoms siloxane framework ligand 1, and not only terminal hydroxyl groups, may be required for coordinative saturation a metal center. This surprising conclusion was drawn from X-ray structure analysis first rare earth complex with this type ligand. Compound 1 serves as molecular model SiO2 supports transition catalysts.

Abstract A new ligand‐ and salt‐free procedure using heterogeneous palladium catalysts for the Larock indole benzofuran synthesis is reported. After optimisation of reaction conditions, good to high isolated yields have been achieved a variety structures. Recycling studies shown that can be readily recovered reused. Reactions recovery carried out in presence air, without any particular precaution.

Abstract The behaviour of several organophosphino‐palladium complexes immobilized on mesoporous silica during the palladium‐catalyzed synthesis propynone by carbonylative Sonogashira coupling was studied, particularly concerning leaching/redeposition phenomena. results demonstrated that this cross‐coupling reaction is catalyzed soluble species. Furthermore, it shown palladium leaching not initiated oxidative addition step but rather palladium‐decoordination from grafted ligand. Despite...

1,2-Addition of the surface silanol groups on SiO2 to nitridomolybdenum fragment title compound and subsequent α-elimination neopentane forms catalytically active species I. This is first case in which an alkylated complex converted into a heterogeneous catalyst well-defined way. The immobilized significantly more ring-opening metathesis polymerization than molecular precursor.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBimetallic activation in homogeneous catalysis. 3. Mechanistic study of the methoxycarbonylation tricarbonyl(chlorobenzene)chromium; isolation and reactivity possible reaction intermediatesVeronique Dufaud, Jean Thivolle-Cazat, Marie Basset, Rene Mathieu, Joel Jaud, Jacqueline WaissermannCite this: Organometallics 1991, 10, 12, 4005–4015Publication Date (Print):December 1, 1991Publication History Published online1 May 2002Published inissue 1...

This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects terms applications are presented according to nature final hybrid material: those based on non-structured silicas, mesostructured macrostructured silicas other oxides. In each part, points synthetic protocols highlighted structural features properties resultant nanocomposites discussed.

A promising route for the double carbonylation of aryl iodide derivatives with secondary and primary amines to produce α-ketoamides is described using covalently immobilized palladium complexes on SBA-15 silica. Adequate adjustments different reaction parameters (temperature, CO pressure, nature base, solvent, substrate…) achieve optimal catalyst performance were made PdCl2(PPh2)2@SBA-15 as catalytic system. High conversions (up 80%) excellent selectivities 96%) carbonylated α-ketoamide...

Hemicryptophanes are host molecules with many applications as supramolecular catalysts or in ion selective recognition. A very convenient and efficient modular approach for the synthesis of hemicryptophane-tren (tren, tris(2-aminoethyl)-amine) derivatives has been developed. For instance, hemicryptophane 1 was synthesized at gram scale four steps from vanillyl alcohol compared to previous seven-step procedure. The size, shape, functionalities molecular cavity were also easily modified.