Naked metal nanoparticles from metal carbonyls in ionic liquids: Easy synthesis and stabilization

An overview with more than 160 references on the synthesis and stabilization of metal nanoparticles (M-NPs) from metal carbonyls, metal salts in ionic liquids (ILs) and in particular from metal carbonyls in ionic liquids is given. The synthesis of M-NPs can proceed by chemical reduction, thermolysis, photochemical decomposition, electroreduction, microwave and sonochemical irradiation. Commercially available metal carbonyls M_x(CO)_y are elegant precursors as they contain the metal atoms already in the zero-valent oxidation state needed for M-NPs. No extra reducing agent is necessary. The side product CO is largely given off to the gas phase and removed from the dispersion. The microwave induced thermal decomposition of metal carbonyls M_x(CO)_y in ILs provides an especially rapid and energy-saving access to M-NPs because of the ILs significant absorption efficiency for microwave energy due to their high ionic charge, high polarity and high dielectric constant. The electrostatic and steric properties of ionic liquids allow for the stabilization of M-NPs without the need of additional stabilizers, surfactants or capping ligands and are highlighted by pointing to the DLVO (Derjaugin–Landau–Verwey–Overbeek) and extra-DLVO theory. Examples for the direct use of M-NP/IL dispersions in hydrogenation catalysis of cyclohexene and benzene are given.     

A green procedure for the protection of carbonyl compounds catalyzed by iodine in ionic liquid

Aldehydes and ketones are protected with ethylene glycol in the presence of a catalytic amount of iodine in PEG ionic liquid (IL 400) under mild conditions to afford the corresponding ketals in good yields. The recovery of iodine is facilitated by the ionic liquid. The recovered catalyst was reused six times with consistent activity.     

Zur Kenntnis der sogenannten «Erdalkalicarbonyle»

The alkaline earth metals in liquid ammonia react with carbon monoxide to form the so-called ‘alkaline earth metal carbonyls’. These products which according to older literature are formulated as M(CO)₂(M = Ca, Sr, Ba) contain only 65–70% of the expected amount of carbon monoxide. As can be seen from the nitrogen content of the compounds the solvent ammonia participates in the reaction. By hydrolysis leading to a variety of compounds it is demonstrated that the ‘alkaline earth metal carbonyls’ are mixtures of substances such as metal acetylenediolates, metal methoxides, and ammonium carbonate. These mixtures are different from the ‘alkali carbonyls’ as for instance can be seen from the low acetylenediolate content of the ‘alkaline earth metal carbonyls’.     

Imidazolium-based phosphinite ionic liquid (IL-OPPh2) as Pd ligand and solvent for selective dehalogenation or homocoupling of aryl halides

The use of an imidazolium-based phosphinite ionic liquid (IL-OPPh₂) as ligand for Pd offers an efficient reagent system for the selective dehalogenation or homocoupling of aryl halides in the presence of NaOPrⁱ or Et₃N, respectively. This ionic liquid plays a dual role as both the reaction media and also as the potential complexing agent with Pd via its phosphinite carrying group. The ionic liquid containing its corresponding Pd complex can be easily recovered and reused in several runs.     

Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

A new low‐energy pathway is reported for the electrochemical reduction of CO₂ to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P₆₆₆₁₄][124Triz] is able to chemisorb CO₂ through equimolar binding of CO₂ with the 1,2,4‐triazole anion. This chemisorbed CO₂ can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO₂ within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P₆₆₆₁₄][NTf₂]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.     

Ceric ammonium nitrate (CAN) as oxidizing or nitrating reagent for organic reactions in ionic liquids

The reaction of ceric ammonium nitrate, (NH₄)₂[Ce(NO₃)₆] or CAN, with naphthalene and 2-methylnaphthalene in the ionic liquid 1-ethyl-3-methylimidazolium triflate showed that the reaction products are strongly dependent on the water content of the ionic liquid and that cerium(IV) in the ionic liquid can electrochemically be regenerated.     

A mild,efficient and improved protocol for the friedländer synthesis of quinolines using lewis acidic ionic liquid

Lewis acidic ionic liquid is shown to be for the first time an excellent medium and efficient catalyst for the synthesis of quinolines at room temperature from o‐amino aromatic carbonyls and ketones containing active methylene group.     

High temperature separation of carbon dioxide/hydrogen mixtures using facilitated supported ionic liquid membranes

Efficiently separating CO₂ from H₂ is one of the key steps in the environmentally responsible uses of fossil fuel for energy production. A wide variety of resources, including petroleum coke, coal, and even biomass, can be gasified to produce syngas (a mixture of CO and H₂). This gas stream can be further reacted with water to produce CO₂ and more H₂. Once separated, the CO₂ can be stored in a variety of geological formations or sequestered by other means. The H₂ can be combusted to operate a turbine, producing electricity, or used to power hydrogen fuel cells. In both cases, only water is produced as waste. An amine-functionalized ionic liquid encapsulated in a supported ionic liquid membrane (SILM) can separate CO₂ from H₂ with a higher permeability and selectivity than any known membrane system. This separation is accomplished at elevated temperatures using facilitated transport supported ionic liquid membranes.     

α-Alkylthio-nitriles via cyanation of thio-acetals and ketals

The reaction of thio-acetals or ketals with cyanotrimethylsilane in the presence of SnCl₄ affords α-alkylthio-nitriles, which can be converted into a variety of other functional groups.     

温和条件下液态醇催化氧化制醛、酮

本文对温和条件下液态醇催化氧化制醛或酮的研究进展进行了全面评述,介绍了均相催化剂、液固多相催化剂、有机相-水相两相催化剂、氟两相催化剂和离子液相催化剂,着重讨论了以O_2为氧源的催化体系.     

Brønsted Acidic Ionic Liquid: An Efficient and Reusable Catalyst for the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones

A novel ionic liquid, 3‐carboxymethyl‐1‐methylimidazolium bisulfate (CMImHSO₄), was synthesized and used as a recyclable catalyst for the Biginelli reaction under solvent‐free conditions. High yields of various substituted 3,4‐dihydropyrimidin‐2(1H)‐ones (or thiones) were obtained. The ionic liquid can be recovered and recycled easily without loss of activity.     

Immobilization of Pd（Ⅱ）Catalysts for Cyclopropanation in Ionic Liquid

Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(Ⅱ） in ionic liquid [omim][BF4] was investigated.Palladium catalysts can be effectively immobilized in ionic liquid.The catalysts PdCl2 and cyclopalladated complex 2 contained in ionic liquid could be recycled for 6 and 7 times,respectively,without losing the efficiency.     

Direct electroreduction of solid cuprous chloride to copper powder in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Direct electroreduction of solid cuprous chloride to prepare copper powder in a “neutral” ambient-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (BMIMBF₄) was investigated. Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid. Chronoamperometry of the salt powder filled Mo-cavity electrode (current collector) in the ionic liquid further demonstrated the conversion of chloride-to metal inside the cavity, as confirmed by scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction spectra.     

离子液体催化剂用于煤焦化苯深度脱硫制无硫苯

从扩大有机合成用苯的需求出发,采用研制的离子液体催化剂考察了煤焦化苯深度脱硫制无硫苯的过程。结果表明：N-甲基咪唑硫酸氢盐[Hmim][HSO₄]离子液体催化剂脱噻吩效果与其酸函数值有关。本文采用Hammett指示剂测定离子液体的酸函数H₀,并得出：在-4至-12的范围,离子液体催化剂可以使煤焦化苯噻吩脱至0. 5mg/L以下。与固体酸催化机理相似,酸量和酸强度一定的离子液体催化剂通过Friedel-Crafts反应形成烷基噻吩等,与苯的物性拉开距离,对苯的分离精制是必不可少的,但是过多、过强的[Hmim][HSO₄]酸值也更有利于苯-噻吩-烯烃共聚合等副反应的发生,从而影响离子液体催化剂重复使用的寿命。本研究利用煤焦化苯脱硫反应形成的噻吩衍生物作为提供电荷流通的聚合物,将反复使用后性能不佳的离子液体成分等作为“受电子型”和“给电子型”的掺杂剂,进行导电（抗静电）材料的制备。结果显示：对煤焦化苯脱硫形成的噻吩衍生物等可以用于掺杂导电材料的试制。     

Solubilization of an Ionic Liquid,l-Butyl-3-methylimidazolium Hexafluorophosphate,in a Surfactant-Water System

The amphiphilic association structures were determined in the system; water, Laureth 4 (approximately C₁₂(EO) ₄), and the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate ([bmim[PF₆]), using visual observation and small angle x-ray diffraction. The system showed a lamellar liquid crystal solubilizing the ionic liquid ([bmim[PF₆]) to a maximum of 15%, an isotropic surfactant solution dissolving the ionic liquid to a maximum of 39%, an isotropic ionic liquid solution with less than 0.5% of water and surfactant and finally, an aqueous solution with only traces of surfactant and ionic liquid. The small angle x-ray diffraction results showed the ionic liquid to be solubilized into the lamellar liquid crystal without changing the dimensions of the amphiphile layer or the interlayer spacing dependence on the water content.     

Thermal,three-carbon + two-atom cycloaddition of cyclopropenone ketals with carbon-heteroatom double bonds: Butenolide,furan, and γ-keto ester preparation.

A preliminary study of the thermal reaction of cyclopropenone ketals with carbon-heteroatom double bonds is detailed. The reaction with aldehyde and keto carbonyls provide butenolide ortho esters, the product of a formal three-carbon + two-atom cycloaddition of the cyclopropenone ketal across the carbon-oxygen double bond.     

An ionic liquid-tagged second generation Hoveyda-Grubbs ruthenium carbene complex as highly reactive and recyclable catalyst for ring-closing metathesis of di-, tri- and tetrasubstituted dienes

A second generation Hoveyda-Grubbs ruthenium carbene complex bearing an ionic liquid tag was prepared and shown to be a highly reactive catalyst for the ring-closing metathesis of di-, tri- and tetrasubstituted diene and enyne substrates in minimally ionic solvent systems ([Bmim]PF₆/CH₂Cl₂, 1:9-1:1 v/v). Both the catalyst and the ionic liquid can be conveniently recycled and repeatedly reused (up to 17 cycles) with only a very slight loss of activity. The ionic liquid tag is crucial to the high level of recyclability of the catalyst since the original second generation Grubbs and Hoveyda-Grubbs catalysts rapidly lose their activity when recycled in the ionic liquid layer.     

磷钼杂多酸离子液体催化氧化脱硫

 合成了新型的磷钼杂多酸离子液体 [hmim]3PMo12O40, 并将其用于室温离子液体 1-甲基咪唑四氟硼酸盐 ([hmim]BF4) 为溶剂的模拟油品氧化脱硫反应. 结果表明, 在温和的反应条件下, 过氧化氢与硫摩尔比为 4:1 时, 二苯并噻吩脱硫率为 90%, 二苯硫醚、苯甲硫醚和二乙硫醚的脱除率可达 100%. 离子液体催化体系循环使用 4 次后, 脱硫率没有明显下降.     

[Bmim]Cl/FeCl3离子液体催化α-生育酚与β-D-五乙酰葡萄糖的糖基化反应

以[Bmim]Cl/FeCl₃(三氯化铁/氯化丁基甲基咪唑)离子液体作为反应介质和催化剂, 考察了离子液体的酸度、反应温度及反应时间对α-生育酚与β-D-五乙酰吡喃型葡萄糖糖基化反应的影响. 结果表明, 离子液体的催化活性与其酸强度密切相关, 离子液体的酸性越强, 其对此糖基化反应催化活性越高. 在FeCl₃与[Bmim]Cl物质的量比为2的[Bmim]Cl/FeCl₃离子液中, α-生育酚与β-D-五乙酰吡喃型葡萄糖在45 ℃下反应3 h, 可以得到较高的转化率, α-生育酚的转化率最高可达70.2%. 同有机溶剂作为反应介质相比, 反应条件温和, 反应时间短, 室温离子液体具有更好的催化活性, 所得产物与离子液体不溶, 便于分离, 催化体系可循环使用, 且对环境友好.     

Microwave-promoted one-pot conversion of alcohols to oximes using 1-methylimidazolium nitrate, [Hmim][NO3], as a green promoter and medium

A wide variety of oximes were prepared from different types of alcohols with hydroxylamine hydrochloride using 1-methylimidaziloum nitrate, [Hmim][NO₃], ionic liquid as a reaction medium and promoter under microwave irradiation. This protocol provides a one-pot oxime synthesis with high yields that is facile, eco-friendly and the ionic liquid can be recovered and reused.