Lewis Basic Ionic Liquid Research Articles

Electrochemical Behavior of Silver Halogenocomplexes in an Amide-Type Ionic Liquid

Silver halides, AgX (X = Cl–, Br–, and I–), are known to be typical poorly soluble salts in aqueous solution. AgX is also almost insoluble in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonly)amide (BMPTFSA). However, AgX has been known to dissolve in the media in the presence of X– by forming halogenocomplexes, [AgX n ](n–1)–. Dissolution of AgCl has been reported in basic chloroaluminate ionic liquids[1] and deep eutectic solvents containing Cl–. In these reports, however, electrochemical behavior of [AgX n ](n–1)– has not been studied in detail. We have already reported that some metal chlorides are soluble in BMPTFSA in the presence of Cl– and that electrodeposition of the metals is possible[2,3]. In the present study, dissolution of AgX has been investigated in BMPTFSA with addition of BMPX. Furthermore, electrodeposition of Ag and electrochemical preparation of Ag nanoparticles have been examined in the Lewis basic ionic liquids. AgX was found to dissolve in BMPTFSA containing 0.5 M BMPX. The dissolved species was determined to be [AgX3]2– by potentiometric technique. The deposition and dissolution of Ag were observed in cyclic voltammetry. The redox potential of [AgX3]2–/Ag was more negative than that of [Ag(TFSA)3]–/Ag and dependent on the kind of halide. The diffusion coefficient of [AgX3]2– was determined by chlonoamperometry. The initial stage of electrodeposition of Ag on a glassy carbon electrode was regarded as progressive. Potentiostatic cathodic reduction of [AgX3]2– resulted in deposition of Ag. The morphology of Ag deposits depended on the reduction potential. Formation of Ag nanoparticles dispersed in the ionic liquid was confirmed after potentiostatic cathodic reduction at a negative potential using transmission electron microscopy[2].

Copper Dissolution in Chloroaluminate Ionic Liquids

The anodic dissolution of metal substrates under convective mass-transport conditions can often lead to considerable improvement of the surface roughness of the substrate through a process known as electropolishing. Electropolishing processes, which are a cornerstone of metal surface finishing, are most commonly carried out in aqueous electrolyte solutions, especially mixtures of concentrated sulfuric and/or phosphoric acids, or in the single acids. However, depending on the metal and conditions used, anodic dissolution in aqueous solutions sometimes results in the formation of unwanted passive films of insoluble salts and/or metal oxides, which limit the efficacy of the electropolishing process. In some circumstances, ionic liquids or room-temperature molten salts may be suitable replacement electrolytes for the aqueous acids commonly used for electropolishing. Among these ionic liquids are the organic salt-based chloroaluminates, such as AlCl3-1-ethyl-3-methylimidazolium chloride (EtMeImCl). Because of their adjustable Lewis acidity, chloroaluminate ionic liquids offer a unique solvation environment for many metals. The Lewis basic AlCl3-EtMeImCl ionic liquids, which contain unbound chloride ion, provide a solvation environment that is not unlike aqueous NaCl, except without the H2O. On the other hand, the AlCl3-rich Lewis acidic ionic liquids are a very different story because there are no “hard” ligands available to form isolable anionic complexes. Nevertheless, many metal ions are very soluble in these ionic liquids. In this investigation, we have focused on the anodic dissolution of copper, not only to assess the utility of acidic and basic chloroaluminates as electrolytes for electropolishing metals, but to understand the kinetics of the electrodissolution of metals in these versatile solvents. As is well known, copper is vitally important in the electronics industry, especially with regard to the preparation of interconnects for computer chips by electrodeposition. As with all electrochemical deposition processes, anode dissolution must be considered in the overall cell reaction. There is also an extensive body of information about the kinetics and mechanism of the anodic dissolution of copper and its alloys under simulated marine conditions, i.e., in aqueous NaCl solutions. Thus, another goal of this investigation is to compare the dissolution of copper in the chloride-rich ionic liquids with dissolution in aqueous chloride solutions. In this presentation, we will describe a kinetic analysis of the anodic dissolution of copper in the Lewis acidic and basic compositions of the AlCl3-EtMeImCl ionic liquid. An example of our research results is given in the figures below. Figure 1 shows current density-time transits recorded at a copper RDE in the Lewis acidic ionic liquid at different potentials and at a fixed rotation rate. Clearly, the current density, j, is potential dependent, but independent of time. Plots of j versus the square root of electrode rotation rate, w1/2, which were constructed from data resulting from a series of experiments similar to those used to produce Fig. 1, are shown in Fig. 2. According to the Levich equation, for a mass transport-limited process, j should show a linear dependence on w1/2 with the line passing through the origin of the plot. This is obviously not the case here, indicating that the dissolution process probably proceeds under mixed control. Figure 3 shows plots of 1/j versus 1/w1/2 based on the Koutecky-Levich equation for a one-electron reaction, 1/j=1/j k + kc /k a [1.61(FD 2/3)-1 ν1/6 ] ω-1/2. These plots clearly show a potential-dependent intercept, indicating a kinetic step in the dissolution process. The interpretation of this data, as well as that resulting from similar experiments conducted in Lewis basic ionic liquids, will be discussed in this presentation. This work was funded by the Strategic Environmental Research and Development Program (SERDP) through contract DE-AC05-00OR22725 to ORNL with subcontract to the University of Mississippi. Figure 1

ChemInform Abstract: Lewis Basic Ionic Liquid as an Efficient and Facile Catalyst for Acetylation of Alcohols, Phenols, and Amines under Solvent‐Free Conditions.

AbstractThe ionic liquid can easily be recovered and used to catalyze further acetylation reactions with excellent yields.

Lewis basic ionic liquid as an efficient and facile catalyst for acetylation of alcohols, phenols, and amines under solvent-free conditions

The Lewis basic ionic liquid 1,8-diazabicyclo[5.4.0]undec-7-en-8-ium acetate was employed for the acetylation of various phenols, alcohols, and amines in good-to-excellent yields at 50 °C under solvent-free conditions in a short time. Compared with existing methods based on conventional catalysts and toxic solvents, the reported method is simple, mild and environmentally viable. Furthermore, the ionic liquid was conveniently separated from the products and easily recycled to catalyze other acetylation reactions with excellent yields. .

Highly efficient SO2 absorption/activation and subsequent utilization by polyethylene glycol-functionalized Lewis basic ionic liquids

Up to now, flue-gas desulfurization (FGD) is one of the most effective techniques to control SO(2) emission from the combustion of fossil fuels. The conventional technology for FGD poses serious inherent drawbacks such as formation of byproducts and volatilization of solvents. In this work, polyethylene glycol (PEG)-functionalized Lewis basic ionic liquids (ILs) derived from DABCO were proved to be highly efficient absorbents for FGD due to its specific features such as high thermal stability, negligible vapor pressure, high loading capacity. Notably, PEG(150)MeDABCONTf(2) gave an extremely high SO(2) capacity (4.38 mol mol(-1) IL), even under 0.1 bar SO(2) partial pressure (1.01 mol mol(-1) IL), presumably owing to the strong SO(2)-philic characterization of the PEG chain. Furthermore, the absorbed SO(2) could be easy to release by just bubbling N(2) at room temperature, greatly reducing energy requirement for SO(2) desorption. In addition, SO(2)/CO(2) selectivity (110) of PEG(150)MeDABCONTf(2) is two times larger than the non-functionalized imidazolium IL (45). On the other hand, through activation of SO(2) with the tertiary nitrogen in the cation, Lewis basic ILs such as PEG(150)MeDABCOBr proved to be efficient catalysts for the conversion of SO(2) to some value-added chemicals such as cyclic sulfites without utilization of any organic solvent or additive. Thus, this protocol would pave the way for the development of technological innovation towards efficient and low energy demanded practical process for SO(2) absorption and subsequent transformation.

ChemInform Abstract: Lewis Basic Ionic Liquid Catalyzed Synthesis of 5‐Aryl‐2‐oxazolidinones from Aziridines and CO2 under Solvent‐Free Conditions.

AbstractTitle agents like [C4DABCO]Br are able to catalyze the cycloaddition of carbon dioxide to aziridines (I) under solvent‐free conditions without any additives.

Lewis Basic Ionic Liquids‐Catalyzed Conversion of Carbon Dioxide to Cyclic Carbonates

AbstractA series of easily prepared Lewis basic ionic liquids were developed for cyclic carbonate synthesis from epoxide and carbon dioxide at low pressure without utilization of any organic solvents or additives. Notably, quantitative yields together with excellent selectivity were attained when 1,8‐diazabicyclo[5.4.0]undec‐7‐enium chloride ([HDBU]Cl) was used as a catalyst. Furthermore, the catalyst could be recycled over five times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of epoxides producing the corresponding cyclic carbonates in high yields and selectivity. Therefore, this solvent‐free process thus represents an environmentally friendly example for the catalytic conversion of carbon dioxide into value‐added chemicals by employing Lewis basic ionic liquids as catalyst. A possible catalytic cycle for the hydrogen bond‐assisted ring‐opening of epoxide and activation of carbon dioxide induced by the nucleophilic tertiary nitrogen of the ionic liquid was also proposed.

Lewis basic ionic liquids-catalyzed synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 under solvent-free conditions

A series of easily prepared Lewis basic ionic liquids were developed as recyclable and efficient catalysts for selective synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 without utilization of any organic solvent or additive. Notably, high conversion, chemo- and regio-selectivity were attained when 1-butyl-4-aza-1-azaniabicyclo[2.2.2]octane bromide ([C4DABCO]Br) was used as the catalyst. Furthermore, the catalyst could be recycled over four times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of aziridines producing the corresponding 5-aryl-2-oxazolidinones in good yields and excellent regioselectivities. Therefore, this solvent-free process thus represents an environmentally friendly process for ionic liquid-catalyzed conversion of CO2 into value-added chemicals. A possible catalytic cycle for CO2 activation induced by nucleophilic tertiary nitrogen of the ionic liquid was proposed, based on studies using in situ FT-IR spectroscopy under CO2 pressure.

Reversible Bromide−Chloride Exchange in Zirconium Cluster Compounds: Synthesis by Means of Ionic Liquids, Structures, and Some Spectral Data of (EMIm)4[(Zr6Z)Br18] Cluster Phases (Z = Be, Fe)

The solid-state precursor cluster chlorides Na(4)[(Zr(6)Be)Cl(16)] and K[(Zr(6)Fe)Cl(15)] readily dissolve in Lewis-basic ionic liquids consisting of mixtures of EMIm-Br and AlBr(3) (EMIm: 1-ethyl-3-methyl-imidazolium) to give dark colored solutions. From these solutions, the cluster phases (EMIm)(4)[(Zr(6)Fe)Br(18)] (1) and (EMIm)(4)[(Zr(6)Be)Br(18)] (2) were obtained in acceptable yields. Crystallographic data of the isostructural phases are the following: monoclinic, P2(1)/c, Z = 2. The data for 1 follow: a = 10.5746(4) Angstrom, b = 22.6567(9) Angstrom, and c = 13.0260(5) Angstrom, beta = 111.279(2) degrees. The data for 2 follow: a = 10.574(2) Angstrom, b = 22.681(4) Angstrom, and c = 13.041(2) Angstrom, beta = 111.31(2) degrees. Compound 1 is the first detailed structurally characterized molecular Fe-centered zirconium bromide cluster phase. In the bromide based ionic liquid, a complete exchange of all the outer and inner chlorides by bromide takes place. Since the inverse reaction, the exchange of all bromides by chlorides, was reported before, this complete ligand exchange can be considered as reversible, with the equilibrium being largely determined by the free ligand concentration. The electronic spectra of a chloride supported cluster precursor in different ionic liquids were measured and analyzed.

Electrochemistry of Iron(III) and Titanium(IV) in the Basic AlBr3 ‐ 1 ‐ Methyl ‐ 3 ‐ ethylimidazolium Bromide Ionic Liquid

Iron(III) and titanium(IV) appear to be complexed as and , respectively, in the Lewis basic ionic liquid. Both species exhibit one electron reversible reduction at a glassy carbon electrode with voltammetric half‐wave potentials of ca. −0.09 and −0.30V, respectively, vs. Al in the 66.7/33.3 mole percent ionic liquid. The half‐wave potentials for both the and systems are very close to values that were measured for the corresponding chloride redox systems in the ionic liquid. The Stokes‐Einstein products for and are , respectively, and are in good agreement with literature values for the corresponding chloride complexes. The introduction of oxide ion into solutions containing by dissolution of appears to produce an oxide bromide complex, possibly, with a voltammetric reduction peak potential of approximately −0.56V, but titanium (IV) appears to react very slowly with oxide that is already present in the melt.