Showing papers on "Halide published in 2002"
TL;DR: Epoxides dissolved in molten tetralkylammonium salts bearing halides as counterions are converted into cyclic carbonates under atmospheric pressure of carbon dioxide.
496 citations
TL;DR: In this paper, a series of low-cost ionic liquids containing methyl and ethyl-sulfate anions can be easily and efficiently prepared under ambient conditions by the reaction of 1-alkylimidazoles with dimethyl sulfate and diethyl sulfate.
493 citations
TL;DR: The metal-halide moiety emerges as a tunable functionality on the transition metal catalyst that can be used in the development of new catalytic systems in stoichiometric and catalytic transition metal processes.
Abstract: Among the most common ligands found on transition metal catalysts are halide ions. Of the commercially available catalysts or pre-catalysts, most are halo-metal complexes. In recent years, manipulation of this metal-halide functionality has revealed that this can be used as a highly valuable method of tuning the reactivity of the complex. Variation of the halide ligand will usually not alter the nature of the system to the extent that it becomes unreactive but will impart sufficiently large changes that differences in reactivity or selectivity occur. These differences are a product of the steric and electronic properties of the halide ligand which has the ability to donate electron density to the metal occurs in a predictable manner. Despite the common perception in asymmetric catalysis that halide ligands are of secondary importance compared to chiral ligands, halide ligands have been found to exert dramatic effects on the enantioselectivity of asymmetric transformations. While the mechanism of action is known for relatively few of the cases, many intriguing and potentially synthetically useful trends are apparent. This review discusses the physical properties of the halides and their effects on stoichiometric and catalytic transition metal processes. The metal-halide moiety thus emerges as a tunable functionality on the transition metal catalyst that can be used in the development of new catalytic systems.
404 citations
TL;DR: A mild and general method for the conversion of aryl, heteroaryl, and vinyl bromides into the corresponding iodides was developed utilizing a catalyst system comprising 5 mol% of CuI and 10 mol % of a 1,2- or 1,3-diamine ligand.
Abstract: A mild and general method for the conversion of aryl, heteroaryl, and vinyl bromides into the corresponding iodides was developed utilizing a catalyst system comprising 5 mol % of CuI and 10 mol % of a 1,2- or 1,3-diamine ligand. A variety of polar functional groups are tolerated, and even N−H containing substrates such as sulfonamides, amides, and indoles are compatible with the reaction conditions. Both the reaction rate and the equilibrium conversion of the aryl bromide depend on the choice of the halide salt and the solvent. The best results were obtained using NaI as the halide salt and dioxane, n-butanol, or n-pentanol as the solvents.
378 citations
Patent•
03 Oct 2002TL;DR: In this article, an ionic liquid is used for cellulose regeneration without the use of harmful or volatile organic solvents, with small cations and halide or pseudohalide anions favoring solution.
Abstract: Cellulose is dissolved in an ionic liquid without derivatization, and is regenerated in a range of structural forms without requiring the use of harmful or volatile organic solvents. Cellulose solubility and the solution properties can be controlled by the selection of the ionic liquid constituents, with small cations and halide or pseudohalide anions favoring solution.
280 citations
TL;DR: In this paper, a spin-coating technique was used to construct thin films of microcrystalline CH3NH3PbX3 and their mixed-halide crystals, and their optical properties were investigated.
Abstract: Thin films of microcrystalline CH3NH3PbX3 (X = halogen) as well as their mixed-halide crystals were fabricated by the spin-coating technique, and their optical properties were investigated. X-ray diffraction investigation revealed that CH3NH3PbBr3 − x
Cl
x
(x = 0–3) were successfully formed on glass substrate self-assembly and oriented with the a-axis. Owing to due to their large exciton binding energy, these materials showed clear exciton absorption and free-exciton emission in the visible region at room temperature. Replacing Br with CI made it possible to control the band structure of these materials. As a result, the peak position of the exciton band shifted continuously towards blue region with increasing the CI content in the films.
275 citations
TL;DR: An ultrasound-assisted preparation of a series of ambient-temperature ionic liquids, 1-alkyl-3-methylimidazolium (AMIM) halides, which proceeds via efficient reaction of 1-methyl imidazole with alkyl halides/terminal dihalides under solvent-free conditions is described.
191 citations
TL;DR: The activation parameters DeltaH(), DeltaS(), and DeltaG() have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.
Abstract: In this work, the nucleophilicities of chloride, bromide, and iodide have been determined in the ionic liquids [bmim][N(Tf)2], [bm2im][N(Tf)2], and [bmpy][N(Tf)2] (where bmim = 1-butyl-3-methylimidazolium, bm2im = 1-butyl-2,3-dimethylimidazolium, bmpy = 1-butyl-1-methylpyrrolidinium, and N(Tf)2 = bis(trifluoromethylsulfonyl)imide). It was found that in the [bmim]+ ionic liquid, chloride was the least nucleophilic halide, but that changing the cation of the ionic liquid affected the relative nucleophilicities of the halides. The activation parameters ΔH⧧, ΔS⧧, and ΔG⧧ have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.
181 citations
TL;DR: Stoichiometric HfO2 films were atomic layer deposited from HfI4 and HfCl4 at 300 °C on p-Si(1 − 0 − 0) substrates as discussed by the authors.
174 citations
TL;DR: In this article, the structure, spectra, and electronic properties of the hydrated fluoride, chloride, bromide, and iodide systems were compared using an enlarged conformational ensemble.
Abstract: Various structures of halide-water pentamers and hexamers have been investigated using extensive ab initio calculations. Then, we compare the structures, spectra, and electronic properties of the hydrated fluoride, chloride, bromide, and iodide systems. Although some of the fluoride and iodide systems have been investigated earlier, we have carried out more accurate calculations on an enlarged conformational ensemble. The chloride-, bromide-, and iodide-water pentamers and hexamers behave somewhat similarly, but differently from the fluoride-water pentamer and hexamer. Fluoride-water clusters show semisurface (or semi-internal) structures, while chloride-, bromide-, and iodide-water clusters show surface structures. We substantiate our findings by evaluating various electronic properties such as ionization potentials, natural bond orbital charges, dipole moments, and charge-transfer-to-solvent energies, as well as vibrational frequencies of the low-energy halide-water pentamers and hexamers.
130 citations
TL;DR: Metathesis of these polyfluoroalkyl-substituted triazolium halides with other salts led to the formation of quaternary compounds, some of which comprise ionic liquids, namely, [R(R(f))-Taz](+)Y(-) (Y = NTf(2), BF(4), PF(6), and OTf), in good isolated yields without the need for further purification.
Abstract: 1,2,4-Triazole was alkylated (alkyl = methyl, butyl, heptyl, decyl) at N-1 in >90% isolated yields. The resulting 1-alkyl triazoles were quaternized at N-4 in >98% isolated yields using fluorinated alkyl halides with >98% isolated yields, under neat reaction conditions at 100−120 °C to form N1-CH3-N4-(CH2)2CmF2m + 1-triazolium (Taz) iodide (m = 1, 6), N1-C4H9-N4-(CH2)2CmF2m + 1-Taz iodide (m = 1, 4, 6), N1-C7H15-N4-(CH2)2CmF2m + 1-Taz iodide (m = 1, 4, 6), N1-C10H21-N4-(CH2)2CmF2m + 1-Taz iodide (m = 1, 4), and N1-CnH2n + 1-N4-(CH2)2F-Taz bromide (n = 4, 7, 10). Single-crystal X-ray analyses confirmed the structure of [1-CH3-4-CH2CH2CF3-Taz]+I-. It crystallized in the orthorhombic space group Pccn, and the unit cell dimensions were a = 13.8289(9) A, b = 17.3603(11) A, c = 9.0587(6) A (α = β = γ = 90°). Metathesis of these polyfluoroalkyl-substituted triazolium halides with other salts led to the formation of quaternary compounds, some of which comprise ionic liquids, namely, [R(Rf)-Taz]+Y- (Y = NTf2, BF4,...
TL;DR: In this paper, the authors examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds.
Abstract: Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade, and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes, and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.
TL;DR: This study for the first time presents transient kinetic measurements of the reactivity of its competent redox intermediate compound I with halides and thiocyanate, using the sequential stopped-flow technique.
Abstract: Lactoperoxidase (LPO) is found in mucosal surfaces and exocrine secretions, including milk, tears, and saliva, and has physiological significance in antimicrobial defense which involves (pseudo-) halide oxidation. This study for the first time presents transient kinetic measurements of the reactivity of its competent redox intermediate compound I with halides and thiocyanate, using the sequential stopped-flow technique. Compound I was produced with either H2O2 [(1.1 ± 0.1) × 107 M-1 s-1] or hypochlorous acid [(3.2 ± 0.1) × 107 M-1 s-1]. At pH 7 and 15 °C, the two-electron reduction of compound I to native LPO by bromide and iodide has a second-order rate constant of (4.1 ± 0.1) × 104 M-1 s-1 and (1.2 ± 0.04) × 108 M-1 s-1, respectively. With thiocyanate the reaction is extremely fast (2.0 × 108 M-1 s-1), whereas chloride cannot function as electron donor. The results are discussed with respect to known kinetic data of homologous mammalian peroxidases and to the physiological role of LPO in antimicrobial d...
TL;DR: In this article, the results of impedance measurements on the corrosion behavior of pure Al, (Al+6%Cu) and (Al +6%Si) alloys in Na 2 SO 4 solutions in the absence and presence of NaCl, NaBr and NaI under the influence of various experimental variables at the open circuit potential (OCP).
TL;DR: In this paper, the authors measured impedance spectra on Au(111) electrode in aqueous perchlorate solutions containing specifically adsorbing anions (SO42−, Cl−, Br− and I−) at potentials where the dominant electrode process is the adsorption of the above anions.
TL;DR: The Suzuki cross-coupling of aries boronic acids with aryl halides, including aries chlorides, proceeds in the phosphonium salt ionic liquid tetradecyltrihexylphosphonium chloride under mild conditions.
TL;DR: In this paper, the melting points of polyhydrates vary insignificantly for different halides, and the highest melting hydrate of tetraisoamylammonium bromide melts at a slightly higher temperature than chloride hydrates, indicating a hydrophilic effect of the anion on clathrate formation.
Abstract: Clathrate formation was considered for two series of systems: (C4H9)4NG–H2O and i‐C5H11)4NG–H2O G = F-, Cl-, Br-, I-). Clathrate hydrates of tetraisoamylammonium halides were shown to melt at higher temperatures than those of the butyl series. In passing from fluoride to bromide, the stability of compounds of the butyl series falls significantly and tetrabutylammonium iodide does not produce polyhydrates. In the isoamyl series, the melting points of polyhydrates vary insignificantly for different halides. In addition, the highest melting hydrate of tetraisoamylammonium bromide melts at a slightly higher temperature than chloride hydrates, indicating not only a hydrophilic effect of the anion on clathrate formation.
Patent•
14 Feb 2002
TL;DR: In this article, a method of treating a coal combustion flue gas, which includes injecting a molecular halogen or thermolabile molecular halogens precursor, such as calcium hypochlorite, is described.
Abstract: A method of treating a coal combustion flue gas, which includes injecting a molecular halogen or thermolabile molecular halogen precursor, such as calcium hypochlorite, able to decompose to form molecular halogen at flue gas temperature. The molecular halogen converts elemental mercury to mercuric halide, which is adsorbable by alkaline solids such as subbituminous or lignite coal ash, alkali fused bituminous coal ash, and dry flue gas desulphurization solids, capturable in whole or part by electrostatic precipitators (ESPs), baghouses (BHs), and fabric filters (FFs), with or without subsequent adsorption by a liquid such as a flue gas desulphurization scrubbing liquor.
TL;DR: In this paper, the role of TBAB on the catalyst stability was discussed, and it was shown that when recovered and reused, the catalyst did not show a significant decrease of activity.
TL;DR: The reaction of tin enolates with alpha-chloro- or bromoketones gave gamma-diketones catalyzed by zinc halides as discussed by the authors, and the reaction with even chlorides was inert to the zinc-catalyzed coupling.
Abstract: The reaction of tin enolates 1 with alpha-chloro- or bromoketones 2 gave gamma-diketones (1,4-diketones) 3 catalyzed by zinc halides. In contrast to the exclusive formation of 1,4-diketones 3 under catalytic conditions, uncatalyzed reaction of 1 with 2 gave aldol-type products 4 through carbonyl attack. NMR study indicates that the catalyzed reaction includes precondensation between tin enolates and alpha-haloketones providing an aldol-type species and their rearrangement of the oxoalkyl group with leaving halogen to produce 1,4-diketones. The catalyst, zinc halides, plays an important role in each step. The carbonyl attack for precondensation is accelerated by the catalyst as Lewis acid and the intermediate zincate promotes the rearrangement by releasing oxygen and bonding with halogen. Various types of tin enolates and alpha-chloro- and bromoketones were applied to the zinc-catalyzed cross-coupling. On the other hand, the allylic halides, which have no carbonyl moiety, were inert to the zinc-catalyzed coupling with tin enolates. The copper halides showed high catalytic activity for the coupling between tin enolates 1 and organic halides 7 to give gamma,delta-unsaturated ketones 8 and/or 9. The reaction with even chlorides proceeded effectively by the catalytic system.
Patent•
08 Nov 2002TL;DR: A series of noble metal organometallic complexes of the general formula (I): MLaXb(FBC)c, wherein M is a noble metal such as iridium, ruthenium or osmium, and L is a neutral ligand such as carbonyl, alkene or diene, X is an anionic ligand, such as chloride, bromide, iodide and trifluoroacetate group, and FBC is a fluorinated bidentate chelate ligand as discussed by the authors.
Abstract: A series of noble metal organometallic complexes of the general formula (I): MLaXb(FBC)c, wherein M is a noble metal such as iridium, ruthenium or osmium, and L is a neutral ligand such as carbonyl, alkene or diene; X is an anionic ligand such as chloride, bromide, iodide and trifluoroacetate group; and FBC is a fluorinated bidentate chelate ligand such as beta diketonate, beta-ketoiminate, amino-alcoholate and amino-alcoholate ligand, wherein a is an integer of from zero (0) to three (3), b is an integer of from zero (0) to one (1) and c is an 10 integer of from one (1) to three (3). The resulting noble metal complexes possess enhanced volatility and thermal stability characteristics, and are suitable for chemical vapor deposition(CVD) applications. The corresponding noble metal complex is formed by treatment of the FBC ligand with a less volatile metal halide. Also disclosed are CVD methods for using the noble metal complexes as source reagents for deposition of noble metal-containing films such as Ir, Ru and Os, or even metal oxide film materials IrO2, OsO2 and RuO2.
TL;DR: In this paper, a cross-coupling reaction of phenylmagnesium bromide with heteroaryl halides, in the presence of a catalytic amount of iron salts, is reported.
TL;DR: In this paper, the crystal structure of the fluoride-containing cage is presented and compared to the previously reported structures of the chloride and bromide-containing cages, in which the silver atoms are held together by a combination of bridging alkynyl groups and Ag⋯Ag metallophilic interactions.
Patent•
20 Dec 2002TL;DR: In this paper, a metal halide film is grown which is then reduced to the metal film rather than growing the metal material directly on the substrate surface, which is the case in this paper.
Abstract: In the present invention, a metal halide film is grown which is then reduced to the metal film rather than growing the metal film directly on the substrate surface. In certain embodiments, a metal halide film is grown from at two precursors: a halogen-containing precursor and a metal-containing precursor. The metal halide film is then exposed to a reducing agent to form the metal film. In certain preferred embodiments, the metal halide film is exposed to the reducing agent prior to the completion of the growing step.
TL;DR: Rapid, direct transition metal-catalyzed C-P(III) cross-coupling reactions were performed by microwave dielectric heating, employing diphenylphosphine and aryl halides/triflates as substrates, with highest yields obtained utilizing heterogeneous or homogeneous Pd or Ni catalysts in DMF or NMP in the presence of KOAc or DABCO as a base.
Patent•
19 Dec 2002TL;DR: In this paper, a metal halide discharge lamp is described, which essentially permits disusing mercury by using a refractory and transparent hermetic vessel, a pair of electrodes fixed to the hermetic vessels, and a discharge medium sealed in the hermetric vessel.
Abstract: Disclosed is a metal halide discharge lamp which essentially permits disusing mercury. The metal halide discharge lamp comprises a refractory and transparent hermetic vessel, a pair of electrodes fixed to the hermetic vessel, and a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide and a rare gas, the first halide being a halide of a metal which achieves a desired light emission, the second halide having a relatively high vapor pressure, being at least one halide of a metal which is unlikely to emit a visible light compared with the metal of the first halide, and acting as a buffer gas.
Patent•
13 May 2002
TL;DR: In this paper, a method of growing single-crystals of a cubic (zinc blende) form of gallium nitride was proposed, which is a method comprising the steps of: placing into a reaction tube or acid resistant vessel a gallium source, anhydrous ammonia, an acid mineralizer and a metal halide salt selected from the group consisting of alkali metal halides, copper halides and tin halides.
Abstract: A method of growing single-crystals of a cubic (zinc blende) form of gallium nitride, the method comprising the steps of: placing into a reaction tube or acid resistant vessel a gallium source, anhydrous ammonia, an acid mineralizer and a metal halide salt selected from the group consisting of alkali metal halides, copper halides, tin halides, lanthanide halides and combinations thereof; closing said reaction tube or vessel; heating said reaction tube; cooling said reaction tube or vessel; and collecting single-crystals of cubic (zinc blende) form of GaN; wherein said reaction tube or vessel has a temperature gradient with a hot zone of at least 250° C., wherein said reaction tube or vessel has a temperature gradient with a cool zone of at least 150° C., and wherein said acid mineralizer has a sufficient concentration to permit chemical transport of GaN in said reaction tube or vessel from said hot zone to said cool zone due to said temperature gradient within said reaction tube or vessel.
TL;DR: In this article, the authors used a coated-wall, low-pressure flow tube coupled to a quadrupole mass spectrometer to study the reaction of HOBr with ice surfaces formed by freezing sodium halide solutions.
Abstract: The heterogeneous reactions of HOBr with ice surfaces formed by freezing sodium halide solutions were studied using a coated-wall, low-pressure flow tube coupled to a quadrupole mass spectrometer. Experiments were conducted at 233 and 248 K with films containing bromide, chloride, or a mixture of the two, and with HOBr gas-phase concentrations of about 1012 molecules/cm3. Gas−surface uptake coefficients and product yields are presented for a range of halide and hydrogen ion concentrations. Compared to analogous reactions with HOCl, HOBr reactions were slower than expected with a maximum uptake coefficient of approximately 0.01. At both 233 and 248 K, gas-phase Br2 was formed exclusively from bromide-only films and only BrCl was formed from chloride films. When both ions were present, BrCl was the sole gas-phase product observed at 233 K, while both gas-phase Br2 and BrCl were formed at 248 K. The relative yields of the gas-phase products depend on the temperature, composition, and acidity of halide-ice su...
TL;DR: In this paper, the condensation of trifluoromethyl -o-phenylenediamines and aromatic aldehydes under microwave irradiation on metal halide supported alumina resulted exclusively triffluoromethsyl-2-aryl benzimidazoles.