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Silver Salt (silver + salt)
Selected AbstractsEfficient Activation of 2-Iminomethylpyridine/Cobalt-Based Alkyne [2+2+2],Cycloaddition Catalyst by Addition of a Silver SaltADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2007Avijit Goswami Abstract The addition of silver triflate (AgOTf) or silver hexafluoroantimonate (AgSbF6) significantly increased the activity of the 2-(arylimino)methylpyridine/cobalt(II) chloride hexahydrate (CoCl2,6,H2O)/zinc catalyst in alkyne cyclotrimerizations thereby accelerating the reaction and enabling the use of unactivated, simple internal alkynes as the monoyne substrate: The rate of reaction was found to be highly dependent on the nature of the counter anion (X,) and the ligand (L) in the postulated cationic cobalt(I) complex [LCo(I)]+X,. [source] ChemInform Abstract: Efficient Synthesis of ,-Oxoalkyl Carbamates from Carbon Dioxide, Internal Propargylic Alcohols, and Secondary Amines Catalyzed by Silver Salts and DBU.CHEMINFORM, Issue 35 2010Chaorong Qi Abstract The cooperation between AgOAc and DBU is a key factor in activating the transformation. [source] ChemInform Abstract: Cyclization of Allenyne-1,6-diols Catalyzed by Gold and Silver Salts: An Efficient Selective Synthesis of Dihydrofuran and Furan Derivatives.CHEMINFORM, Issue 27 2008Sundae Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Conversion of Alkyl Halides into Alcohols via Formyloxylation Reaction with DMF Catalyzed by Silver Salts.CHEMINFORM, Issue 16 2006Antonio Abad Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Selective extraction of polyunsaturated triacylglycerols using a novel ionic liquid precursor immobilized on a mesoporous complexing adsorbentBIOTECHNOLOGY PROGRESS, Issue 5 2009Patrisha J. Pham Abstract Mesoporous silica (SBA-15) synthesized by using Pluronic123 as the structure-directing template was functionalized by imidazolium-based ionic liquid precursors. Silver salts were then immobilized onto the supported ionic liquids using the incipient wetness impregnation technique. The separation of unsaturated species was achieved through the reversible and specific interaction between silver ions and carbon,carbon double bonds. This adsorbent was examined for the selective separation of polyunsaturated triacylglycerols (PUTAG) using High Pressure Liquid Chromatography (HPLC) with Evaporative Light Scattering Detection (ELSD) as the quantification methodology. AgBF4/SBA15·HPSiOEtIM·PF6 showed an adsorption capacity for linolenin of about 217 mg adsorbed/gram of sorbent. This adsorbent had good selectivity and a high capacity for the most highly unsaturated triacylglycerol when applied to a mixture of triacylglycerols with varying degrees of unsaturation. Consequently, a stepwise methodology was also developed to increase the recovery of the adsorbed components. This adsorbent retained its selectivity and capacity when recycled up to five times. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Alkyne Hydroarylations with Chelating Dicarbene Palladium(II) Complex Catalysts: Improved and Unexpected Reactivity Patterns Disclosed Upon Additive Screening,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Andrea Biffis Abstract Palladium(II) complexes with a ligand set made from a chelating N-heterocyclic dicarbene ligand and two weakly coordinating anions (generally introduced in situ upon addition of 2 equiv. of a suitable silver salt) were found to be very active and selective catalysts for the room-temperature hydroarylation of alkynes at low catalyst loading (0.1 mol-%). Moreover, the screening of various strong acids as reaction promoters revealed that both the strength of the acid and the coordinating ability of its conjugated base influence the catalytic performance. Most remarkably, the use of HBF4 together with a dicarbene Pd complex catalyst provides a dramatic change in the selectivity of the reaction, with the prevalent formation of a product stemming from the insertion of two molecules of alkyne into the aromatic C,H bond. The results presented herein highlight the fact that the dicarbene ligand, apart from stabilising the catalyst, is also able to enhance catalytic activity and, most notably, to steer the reaction selectivity towards novel products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Pattern Formation of Silver Nanoparticles in 1-, 2-, and 3D Microstructures Fabricated by a Photo- and Thermal Reduction MethodADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Jong-Jin Park Abstract One-, two-, and three-dimensional microstructures with dispersed silver nanoparticles are fabricated by a combination of photopatterning and thermal treatment from a silver salt containing photosensitive epoxy resin. Ultraviolet photo-irradiation and subsequent thermal treatment are combined to control the rate of silver salt reduction, the size and the arrangement of nanoparticles, as well as the reticulation of the epoxy resin. This approach allows the creation of high resolution 1-, 2-, and 3D patterns containing silver nanoparticles, with a homogeneous distribution of nanoparticles regardless of the irradiated area. [source] Cationic Ruthenium-Cyclopentadienyl-Diphosphine Complexes as Catalysts for the Allylation of Phenols with Allyl Alcohol; Relation between Structure and Catalytic Performance in O - vs.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009C -Allylation Abstract A new catalytic method has been investigated to obtain either O - or C -allylated phenolic products using allyl alcohol or diallyl ether as the allyl donor. With the use of new cationic ruthenium(II) complexes as catalyst, both reactions can be performed with good selectivity. Active cationic Ru(II) complexes, having cyclopentadienyl and bidentate phosphine ligands are generated from the corresponding Ru(II) chloride complexes with a silver salt. The structures of three novel (diphosphine)Ru(II)CpCl catalyst precursor complexes are reported. It appears that the structure of the bidentate ligand has a major influence on catalytic activity as well as chemoselectivity. In addition, a strong cocatalytic effect of small amounts of acid is revealed. Model experiments are described that have been used to build a reaction network that explains the origin and evolution in time of both O -allylated and C -allylated phenolic products. Some mechanistic implications of the observed structure vs. performance relation of the [(diphosphine)RuCp]+ complexes and the cocatalytic role of added protons are discussed. [source] Heterogenization of a Modified Grubbs,Hoveyda Catalyst on a ROMP-Derived Monolithic SupportMACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2003Jens O. Krause Abstract A ring-opening metathesis polymerization- (ROMP-) based monolith was synthesized using a Grubbs' first generation catalyst. The living termini were used for surface grafting of norborn-5-ene-2-ylmethyl hexafluoroglutarate. The free carboxylic acid groups of the graft polymer were converted into the corresponding silver salt and reacted with the Grubbs,Hoveyda catalyst [RuCl2(CH(2- iPrO)C6H4)(IMesH2)] (IMesH2,=,1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) to yield a stable heterogeneous version of this catalyst for use in ring-closing metathesis (RCM) under continuous flow conditions. The monolith-supported Grubbs,Hoveyda catalyst. [source] Nanocomposites of silver nanoparticle and dinonylnaphthalene disulfonic acid-doped thermoreversible polyaniline gelPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Ashesh Garai Silver/polyaniline-dinonylnaphthalene disulfonic acid (PANI-DNNDSA) gel nanocomposites are prepared from the reduction of silver salt by polyaniline in formic acid medium. Scanning electron micrographs (SEM) indicate the presence of three-dimensional fibrillar network structure and the silver nanoparticles remain dispersed within the PANI-DNNDSA fibrillar network. Differential scanning calorimetric (DSC) study shows reversible first-order phase transition characterizing the composite to behave as a thermoreversible gel. Transmission electron micrographs (TEM) show a decrease of nanoparticle size with increasing AgNO3 concentration. Wide angle X-ray scattering (WAXS) patterns show lamellar structure in the gel as well as in the gel metal nanocomposites (GMNCs) and the two melting peaks in the DSC patterns correspond to the melting of monolayer and bilayer crystals produced from the interdigitation of DNNDSA tails anchored from PANI chains within the PANI lamella. The above melting points are greater in the GMNCs than that of pure gel indicating the formation of complex melting thermogram with crystallites produced from the anchored surfactants tails at the surface of Ag nanoparticles. The GMNCs show a higher thermal stability than that of pure PANI-DNNDSA gel. PANI-DNNDSA gel has an emission peak at 354 nm but fluorescence quenching occurs in the GMNCs and the emission peak becomes red shifted. Also in the UV,vis spectra the , band-polaron band transition peak shows a red shift and the DC conductivity increases with increasing Ag nanoparticle concentration in the GMNCs. The current (I),voltage (V) characteristic curves indicate Ohmic nature of conductivity of the gel and the current at the same voltage increases appreciably with increasing Ag nanoparticle concentration. These GMNCs are easily processible due to its thermoreversible nature. So, an easily processible, thermally stable and highly conducting DNNDSA-doped PANI-Ag gel nanocomposite with interesting photoluminescent property has been successfully developed suitable for optoelectronic applications. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] [(NHC)AuI]-Catalyzed Formation of Conjugated Enones and Enals: An Experimental and Computational StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2007Nicolas Marion Abstract The [(NHC)AuI]-catalyzed (NHC = N-heterocyclic carbene) formation of ,,,-unsaturated carbonyl compounds (enones and enals) from propargylic acetates is described. The reactions occur at 60,°C in 8,h in the presence of an equimolar mixture of [(NHC)AuCl] and AgSbF6 and produce conjugated enones and enals in high yields. Optimization studies revealed that the reaction is sensitive to the solvent, the NHC, and, to a lesser extent, to the silver salt employed, leading to the use of [(ItBu)AuCl]/AgSbF6 in THF as an efficient catalytic system. This transformation proved to have a broad scope, enabling the stereoselective formation of (E)-enones and -enals with great structural diversity. The effect of substitution at the propargylic and acetylenic positions has been investigated, as well as the effect of aryl substitution on the formation of cinnamyl ketones. The presence or absence of water in the reaction mixture was found to be crucial. From the same phenylpropargyl acetates, anhydrous conditions led to the formation of indene compounds via a tandem [3,3] sigmatropic rearrangement/intramolecular hydroarylation process, whereas simply adding water to the reaction mixture produced enone derivatives cleanly. Several mechanistic hypotheses, including the hydrolysis of an allenol ester intermediate and SN2, addition of water, were examined to gain an insight into this transformation. Mechanistic investigations and computational studies support [(NHC)AuOH], produced in situ from [(NHC)AuSbF6] and H2O, instead of cationic [(NHC)AuSbF6] as the catalytically active species. Based on DFT calculations performed at the B3LYP level of theory, a full catalytic cycle featuring an unprecedented transfer of the OH moiety bound to the gold center to the CC bond leading to the formation of a gold,allenolate is proposed. Es descriu la reacció de formació de compostos de carbonil ,,, -insaturats (enones i enals) a partir d,acetats propargílics catalitzada per [(NHC)AuI] (NHC=carbè N-heterocíclic). Les reaccions tenen lloc a 60,°C en 8,h en presència d,una mescla equimolar de [(NHC)AuCl] i AgSbF6 i produeix rendiments alts d,enones i enals conjugats. Estudis d,optimització van mostrar que la reacció era sensible al solvent, el NHC, i, en menor grau, a la natura de la sal de plata emprada; això va portar a escollir [(ItBu)AuCl]/AgSbF6 en THF com a sistema catalític eficient. La transformació va mostrar posseir un ampli espectre, i es va aconseguir la formació estereoselectiva d,(E)-enones i -enals amb gran diversitat estructural. La influència de la substitució en les posicions propargílica i acetilènica va ser investigada, així com la substitució d,aril per donar lloc a la formació de cinamilcetones. La presència o absència d,aigua en el medi de reacció es va mostrar com a crucial. A partir dels mateixos fenilpropargilacetats, condicions anhidres van portar a la formació de compostos indènics mitjançant una reacció tàndem de reorganització sigmatròpica [3,3] i hidroarilació intramolecular, mentre que l,addició d,aigua a la reacció portava de manera neta a derivats del tipus enona. Diverses hipòtesis mecanístiques, entre elles la hidròlisi d,un intermedi del tipus al.lenol ester i l,addició SN2, d,aigua, han estat examinades per millorar la comprensió del procés. Les dades mecanístiques i els estudis computacionals suggereixen que l,espècie catalítica activa és [(NHC)AuOH], produït in situ a partir de [(NHC)AuSbF6] i H2O, i no el complex catiònic [(NHC)AuSbF6]. A partir d,estudis DFT realitzats al nivell B3LYP, es proposa un cicle catalític complet, que inclou un nou tipus d,etapa consistent en la transferència d,un grup OH des de l,or cap a l,enllaç CC per produir un complex or-al.lenolat. [source] Gold(I) Complexes of P,N Ligands and Their Catalytic ActivityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2010Chosu Khin Abstract Gold(I) complexes were readily prepared by reaction of the respective ligands with (Me2S)AuCl in CH2Cl2. Complexes of formula LAuCl {L = diphenyl(2-pyridyl)phosphane (PPh2Py), (R)-(+)-4-[(2)-(diphenylphosphanyl)-1-naphthyl]- N -[(R)-1-phenylethyl]-1-phthalazinamine (PINAP)} were obtained when a 1:1 molar ratio of ligand to starting gold precursor was used. When a 2:1 ratio of ligand to gold precursor was used with PPh2Py or MandyPhos as ligands, complexes of the type L2AuCl were obtained. All complexes were fully characterized, and single-crystal X-ray structures could be determined for four complexes. Chloride ions were removed by reaction with silver salts, such as AgNTf2, AgOTf and AgBF4, for the use of these complexes as catalysts. After the catalytic reaction with alkynes and alcohols in acetonitrile, a unique trinuclear gold(I) complex derived from [(PPh2Py)Au]BF4 could be characterized by X-ray structural analysis, showing a mode of catalyst deactivation. [source] Anion-Dependent Structural Diversity in Silver(I) Complexes of 4-Amino-3,5-diisopropyl-1,2,4-triazoleEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2007Guang Yang Abstract Reactions of silver salts with 4-amino-3,5-diisopropyl-1,2,4-triazole (L) afford dinuclear complex [Ag2L2(NO3)2(CH3CN)], triangular complex [Ag3L3](CF3SO3)3, and cyclic tetranuclear complexes [Ag4L6](BF4)4 and [Ag4L6](ClO4)4. On the basis of the X-ray analyses, anions are found to play an important role in determining the structures. Through coordination/noncoordination, anions can impart their influence on the coordination geometry of Ag atoms and the angles of N,Ag,N, which seems to be the main factor controlling the nuclearity of the reaction products in this system. 1H NMR and MS measurements suggest that these complexes probably retain their structural integrities in CH3CN solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Surface enhanced Raman scattering of trans-p-coumaric and syringic acidsJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009R. E. Clavijo Abstract The vibrational spectra of trans-p-coumaric acid (pCA) and syringic acid (SA) are discussed. The spectral fingerprints of the organic acids observed in the infrared and Raman spectra are assigned to fundamental vibrational wavenumbers supported by quantum chemical computations. The average surface-enhanced Raman scattering spectra of both acids have been obtained on silver colloidal solutions and the interpretation of the spectra is presented based on complementary Raman spectra and computational results for the silver salts. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||