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Imidazolium Salts (imidazolium + salt)
Selected AbstractsLiquid Crystal Imidazolium Salts: Towards Materials for Catalysis and Molecular ElectronicsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2007Jean-Moïse Suisse Abstract 1,3-Bis(4-alkyloxyphenyl)-3H -imidazol-1-ium trifluoromethanesulfonates, alkyl = CH3(CH2)n,1, n = 8, 10, 12, 14 and 16, can be derived from the analogous 4-alkyloxyphenylamines. These imidazolium salts exhibit a lamellar liquid-crystal mesophase between 99 °C and 191 °C. The smectic-A phase was fully characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. We report also the synthesis, lamellar crystal structure and catalytic activity of the PdII complex of the (deprotonated) carbene form of one of these salts. In addition, we measured the charged carrier mobilities in the mesophase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] ChemInform Abstract: Imidazolium Salts with a Free Carboxy Group as New Catalysts of the Biginelli Reaction.CHEMINFORM, Issue 41 2010F. Makaev No abstract is available for this article. [source] Imidazolium Salts as Specific Catalysts for Michael Addition to Nitroalkanes: A Structure,Catalyst Efficiency Relationship.CHEMINFORM, Issue 48 2007Electron A. Mistryukov 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] Unexpected Microwave Reaction of 1,3-Disubstituted Imidazolium Salts: A Novel Synthesis of 1,3-Disubstituted Imidazole-2-thiones.CHEMINFORM, Issue 26 2007Xiao-Le Tao 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] Preparation of Functionalized Imidazolium Salts under Microwave Irradiation.CHEMINFORM, Issue 46 2006Shih-Kang Fu 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] Dual-Functionalized Ionic Liquids: Synthesis and Characterization of Imidazolium Salts with a Nitrile-Functionalized Anion.CHEMINFORM, Issue 13 2005Dongbin Zhao Abstract For Abstract see ChemInform Abstract in Full Text. [source] Polymer-Supported Ionic Liquids: Imidazolium Salts as Catalysts for Nucleophilic Substitution Reactions Including Fluorinations.CHEMINFORM, Issue 20 2004Dong Wook Kim Abstract For Abstract see ChemInform Abstract in Full Text. [source] [(NHC)(NHCewg)RuCl2(CHPh)] Complexes with Modified NHCewg Ligands for Efficient Ring-Closing Metathesis Leading to Tetrasubstituted Olefins,CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2010Volodymyr Sashuk Abstract Imidazolium salts (NHCewg,HCl) with electronically variable substituents in the 4,5-position (H,H or Cl,Cl or H,NO2 or CN,CN) and sterically variable substituents in the 1,3-position (Me,Me or Et,Et or iPr,iPr or Me,iPr) were synthesized and converted into the respective [AgI(NHC)ewg] complexes. The reactions of [(NHC)RuCl2(CHPh)(py)2] with the [AgI(NHCewg)] complexes provide the respective [(NHC)(NHCewg)RuCl2(CHPh)] complexes in excellent yields. The catalytic activity of such complexes in ring-closing metathesis (RCM) reactions leading to tetrasubstituted olefins was studied. To obtain quantitative substrate conversion, catalyst loadings of 0.2,0.5,mol,% at 80,°C in toluene are sufficient. The complex with the best catalytic activity in such RCM reactions and the fastest initiation rate has an NHCewg group with 1,3-Me,iPr and 4,5-Cl,Cl substituents and can be synthesized in 95,% isolated yield from the ruthenium precursor. To learn which one of the two NHC ligands acts as the leaving group in olefin metathesis reactions two complexes, [(FL-NHC)(NHCewg)RuCl2(CHPh)] and [(FL-NHCewg)(NHC)RuCl2(CHPh)], with a dansyl fluorophore (FL)-tagged electron-rich NHC ligand (FL-NHC) and an electron-deficient NHC ligand (FL-NHCewg) were prepared. The fluorescence of the dansyl fluorophore is quenched as long as it is in close vicinity to ruthenium, but increases strongly upon dissociation of the respective fluorophore-tagged ligand. In this manner, it was shown for ring-opening metathesis ploymerization (ROMP) reactions at room temperature that the NHCewg ligand normally acts as the leaving group, whereas the other NHC ligand remains ligated to ruthenium. [source] Adducts of Aluminum and Gallium Trichloride with a N -Heterocyclic Carbene and an Adduct of Aluminum Trichloride with a ThioneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004Andreas Stasch Abstract The reactions of AlCl3 and GaCl3 with 1,3,4,5-tetramethylimidazole-2-ylidene in toluene at room temperature affords the 1:1 adducts 5 and 6, respectively. The use of a bulky N -heterocyclic carbene (NHC) in toluene/THF and AlCl3 results in the formation of an imidazolium salt 7 with the tetrachloroaluminate anion. A 1:1 adduct 8 of 1,3,4,5-tetramethylimidazole-2(3H)-thione with AlCl3 is obtained in toluene. The crystal structures of 5·0.5C7H8, 7·THF and 8 were determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] TEMPO and Carboxylic Acid Functionalized Imidazolium Salts/Sodium Nitrite: An Efficient, Reusable, Transition Metal-Free Catalytic System for Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Cheng-Xia Miao Abstract An effective catalytic system comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) functionalized imidazolium salt ([Imim-TEMPO]+,X,), a carboxylic acid substituted imidazolium salt ([Imim-COOH]+,X,), and sodium nitrite (NaNO2) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to >99%, even at ambient conditions. Notably, the catalyst system could preferentially oxidize a primary alcohol to the aldehyde rather than a secondary alcohol to the ketone. Moreover, the reaction rate is greatly enhanced when a proper amount of water is present. And a high turnover number (TON 5000) is achieved in the present transition metal-free aerobic catalytic system. Additionally, the functionalized imidazolium salts are successfully reused at least four times. This process thus represents a greener pathway for the aerobic oxidation of alcohols into carbonyl compounds by using the present task-specific ionic liquids in place of the toxic and volatile additive, such as hydrogen bromide, bromine, or hydrogen chloride (HBr, Br2 or HCl), which is commonly required for the transition metal-free aerobic oxidation of alcohols. [source] A Straightforward Procedure for the [2+2+2],Cycloaddition of EnediynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Anaïs Geny Abstract Enediynes undergo intramolecular [2+2+2],cycloaddition in the presence of cobalt(II) iodide (CoI2), manganese and an N-heterocyclic carbene (IPr) generated in situ from the corresponding imidazolium salt and butyllithium (BuLi). Polycyclic cyclohexadienes are obtained selectively. This new method represents an interesting alternative to those employing air-sensitive cyclopentadienylcobalt [CpCoL2 (L=CO, C2H4)] catalysts. Moreover, the N-heterocyclic carbene can be used catalytically, which is a significant improvement compared to the corresponding phosphine-based system which requires an excess of ligand. [source] Ring-opening metathesis polymerization of functionalized cyclooctene by a ruthenium-based catalyst in ionic liquidJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007Huijing Han Abstract This paper describes the synthesis of a novel monomer of 5-substituted cyclooctene with the pendant of imidazolium salt (7) and the ring-opening metathesis polymerization of the functionalized cyclooctenes (4 and 7) in CH2Cl2 and ionic liquid [bmim][PF6] by a ruthenium-based catalyst RuCl2(PCy3)(SIMes)(CHPh) (2). The polymerization, which was carried out in ionic liquid, afforded improved control over the molecular weight (Mn) and polydispersity of the resultant products (PDI <1.4). Furthermore, to facilitate the GPC measurement for molecular weight of polymers, the charged polymers (poly- 7) were hydrolyzed to give uncharged polymers (poly- 4*) by removing the imidazolium pendant from the polymer chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3986,3993, 2007 [source] Imidazolium based ionic liquid crystals: structure, photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1)CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008A. Getsis Abstract The long chain imidazolium halides [Cnmim]Br·xH2O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X-ray structure analyses of the monohydrates ([C12mim]Br·H2O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, , = 81.89(5)°, , = 83.76(5)°, , = 78.102(5)°, 3523 unique reflections with Io > 2,(Io), R1 = 0.0263, wR2 = 0.0652, GooF = 1.037, T = 263(2) K; [C14mim]Br,H2O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, , = 94.86(2)°, , = 94.39(2)°, , = 101.83(2)°, 2063 unique reflections with Io > 2,(Io), R1 = 0.0429, wR2 = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (1,,1,*) and long lived (1,,3,*) transitions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Simple Building-Block Route to (Phosphanyl-carbene)palladium Complexes via Intermolecular Addition of Functionalised Phosphanes to IsocyanidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2009Michael R. Eberhard Abstract We present a straightforward protocol for making (phosphanyl-carbene)PdII complexes. These complexes have bidentate ligands containing an acyclic diamino- or aminooxy-carbene and a phosphane. The synthesis gives good yields (typically 70,90,%) for a variety of complexes (22 compounds). Moreover, it does not require the synthesis of imidazolium salts nor the a priori generation of free carbenes. Three of the new complexes were tested as catalysts for Sonogashira and Hay coupling reactions, with good yields and selectivities. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Liquid Crystal Imidazolium Salts: Towards Materials for Catalysis and Molecular ElectronicsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2007Jean-Moïse Suisse Abstract 1,3-Bis(4-alkyloxyphenyl)-3H -imidazol-1-ium trifluoromethanesulfonates, alkyl = CH3(CH2)n,1, n = 8, 10, 12, 14 and 16, can be derived from the analogous 4-alkyloxyphenylamines. These imidazolium salts exhibit a lamellar liquid-crystal mesophase between 99 °C and 191 °C. The smectic-A phase was fully characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. We report also the synthesis, lamellar crystal structure and catalytic activity of the PdII complex of the (deprotonated) carbene form of one of these salts. In addition, we measured the charged carrier mobilities in the mesophase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Designing Ionic Liquids: 1-Butyl-3-Methylimidazolium Cations with Substituted Tetraphenylborate CounterionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2003Joep van den Broeke Abstract The hydrophobic, low melting, 1-butyl-3-methylimidazolium (BMIm) salts [BMIm][BPh4] (1), [BMIm][B(C6H4Me-4)4] (2), [BMIm][B{C6H4(CF3)-4}4] (3), [BMIm][B{C6H3(CF3)2 -3,5}4] (4), [BMIm][B{C6H4(C6F13)-4}4] (5), [BMIm][B{C6H4(SiMe3)-4}4] (6), [BMIm][B(C6H4{SiMe2(CH2CH2CF3)}-4)4] (7), [BMIm][B{C6H4(SiMe2C8H17}-4}4] (8) and [BMIm][B(C6H4{SiMe2(CH2CH2C6F13)}-4)4] (9) have been prepared. Systematic variation of the substituents on the tetraphenylborate anion allowed an assessment of their influence on the physical properties of the imidazolium salts. Structural investigations using NMR and IR spectroscopy, combined with single crystal X-ray structure determinations for 2, 3, 5 and 6, revealed hydrogen-bonding interactions between the imidazolium ring protons and the borate anion, both in the solid state and in solution. These interactions are weakened upon the introduction of electron-withdrawing substituents in the anion and follow the order 3,5-(CF3)2 < ,C6F13 < ,CF3 < ,SiMe2CH2CH2C6F13 < ,SiMe2CH2CH2CF3 < ,H < ,Me < ,SiMe3. The melting points of the salts depend primarily on the bulk of the lipophilic substituents, and decrease with increasing size. Bulky lipophilic substituents dramatically enhance the solubility of the imidazolium borates 8 and 9 in hexane and reduce their relative polarity. These unique properties make imidazolium borates 8 and 9 interesting as amphiphilic ionic liquids with low polarity. Attempts to crystallise 7 resulted in decomposition. A single-crystal X-ray structure determination of the product, isolated in 6% yield, showed that a carbene,tris[4-{dimethyl(3,3,3-trifluoropropyl)silyl}phenyl]borane adduct was formed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] TEMPO and Carboxylic Acid Functionalized Imidazolium Salts/Sodium Nitrite: An Efficient, Reusable, Transition Metal-Free Catalytic System for Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Cheng-Xia Miao Abstract An effective catalytic system comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) functionalized imidazolium salt ([Imim-TEMPO]+,X,), a carboxylic acid substituted imidazolium salt ([Imim-COOH]+,X,), and sodium nitrite (NaNO2) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to >99%, even at ambient conditions. Notably, the catalyst system could preferentially oxidize a primary alcohol to the aldehyde rather than a secondary alcohol to the ketone. Moreover, the reaction rate is greatly enhanced when a proper amount of water is present. And a high turnover number (TON 5000) is achieved in the present transition metal-free aerobic catalytic system. Additionally, the functionalized imidazolium salts are successfully reused at least four times. This process thus represents a greener pathway for the aerobic oxidation of alcohols into carbonyl compounds by using the present task-specific ionic liquids in place of the toxic and volatile additive, such as hydrogen bromide, bromine, or hydrogen chloride (HBr, Br2 or HCl), which is commonly required for the transition metal-free aerobic oxidation of alcohols. [source] Supramolecular encapsulation of 1,3-bis(1-adamantyl)imidazolium chloride by ,-cyclodextrins: towards inhibition of C(2)-H/D exchangeJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2009Loïc Leclercq Abstract The study of the hydrogen/deuterium exchange reactions of the C(2)-proton for different carbene precursors has been carried out in the absence and presence of ,-cyclodextrin in D2O at 25°C. Formation of the inclusion complexes of imidazolium salts with the native ,-cyclodextrin and the ,-dimethylcyclodextrin is demonstrated by 1D and 2D 1H NMR, ESI/HRMS and a molecular modelling study. Formation of the inclusion complexes of imidazolium salts with the native ,-cyclodextrin and the ,-dimethylcyclodextrin is a simple and efficient method to modify the acidity of the imidazolium H(2) and to modify its environment. Encapsulation of 1,3-disubstituted imidazolium chloride by ,-cyclodextrins results in the inhibition of the H(2)/D exchange in the complex. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effect of hydrophobic side-chains on the solvation of imidazolium saltsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2005Allan D. Headley Abstract The chemical shifts of the aromatic hydrogens of 12 symmetrical imidazolium salts were determined in different deuterated solvents. Based on the magnitude of the chemical shift change for the hydrogens of the imidazolium ion in the various solvents, relationships were developed to determine the relative solute/solvent interactions for these compounds. Owing to different degrees of interactions involving the aromatic hydrogens of the imidazolium cations and anions, there is a variation in the interaction of the hydrogens with the solvent molecules. The intimate interaction that exists between the hydrogens of the imidazolium cation and the BF anion results in the BF salts being less solvated compared with salts containing BF and SbF anions. For imidazolium salts that contain C2H5, C4H9 and C8H17 side-chains bonded in the 1 and 3 positions, the interaction between H2 and the solvents was observed to be greater than for imidazolium salts with C16H33 substituents. On the other hand, for imidazolium salts that have C16H33 substituents the interaction between H2 and the solvents is similar to that for H4 and H5. Copyright © 2005 John Wiley & Sons, Ltd. [source] ChemInform Abstract: Rational Exploration of N-Heterocyclic Carbene (NHC) Palladacycle Diversity: A Highly Active and Versatile Precatalyst for Suzuki,Miyaura Coupling Reactions of Deactivated Aryl and Alkyl Substrates.CHEMINFORM, Issue 39 2010Guang-Rong Peh Abstract A small library of NHC-palladacycles is prepared by heating readily available palladacycle acetates with imidazolium salts. [source] | |||||||||||||