Crestina S. Consorti

Water-induced accelerated ion diffusion: voltammetric studies in 1-methyl-3-[2,6-(S)-dimethylocten-2-yl]imidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ionic liquids

The electrochemical properties of the room temperature ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM+BF4−), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6−) and 1-methyl-3-[2,6-(S)-dimethylocten-2-yl]imidazolium tetrafluoroborate (MDIM+BF4−) as solvents have been studied using micro-samples, with a volume of 10 μL, of the ionic liquids under vacuum conditions and under conditions with controlled gas and moisture supplies. The impact of water—absorbed into the ionic liquid in a controlled manner from the gas phase—on the voltammetry of dissolved redox systems and on the accessible potential window of the ionic liquids was investigated. The diffusion coefficients for three representative redox systems, the oxidation of neutral N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), the reduction of cationic methyl viologen (MV2+) and reduction of anionic hexacyanoferrate(III), Fe(CN)63−, have been determined as a function of the water content of the ionic liquids. Water is shown to have a much more dramatic acceleration effect on the diffusion of the ionic compounds compared to its effect on neutral species in ionic liquids. A model based on nanoscale structural features of wet ionic liquid materials is proposed. The novel methodology, which employs redox-active compounds dissolved or partitioned in microdroplets of ionic liquid, uses conditions suitable for the study of ionic liquids for applications in electrochemical gas phase reactors and gas sensor systems.

Room temperature molten salts: neoteric "green" solvents for chemical reactions and processes

Liquidos ionicos, em particular aqueles de rivados do cation 1,3-dialquilimidazolio, que possuem uma ampla faixa de temperatura em suas fases liquidas, pressoes de vapores muito pequenas, baixas viscosidades e elevada estabilidade termica e quimica vem emergindo como uma nova classe de solventes “verdes” para processos de extracao e separacao, sintese orgânica e catalise. Os principais resultados obtidos com estes liquidos em Quimica Limpa nos ultimos dois anos sao objeto deste artigo de revisao. Ionic liquids, especially those based on the 1,3-dialkylimidazolium cation, with a large range of liquid phase, negligible vapour pressure, low viscosity and high thermal and chemical stability are emerging as a new class of ‘green’ solvents for extraction and separation processes, organic synthesis and catalysis. The main milestones reached in the last two years, on the use of ionic liquids in green technologies, are reviewed.

Ionic liquid modified electrodes. Unusual partitioning and diffusion effects of Fe(CN)64−/3− in droplet and thin layer deposits of 1-methyl-3-(2,6-(S)-dimethylocten-2-yl)-imidazolium tetrafluoroborate

Room temperature ionic liquids exhibit unusual and, for electrochemical applications, promising properties such as ionic conductivity and non-volatility. Microdroplet and thin film deposits of an ionic liquid, 1-methyl-3-(2,6-(S)-dimethylocten-2-yl)-imidazolium tetrafluoroborate (MDIM+BF4−) on electrode surfaces are studied in order to assess the ability of aqueous ions to partition into the ionic liquid. Two complementary methodologies, deposition of ionic liquid onto a 4.9 mm diameter basal plane pyrolytic graphite electrode followed by voltammetric analysis and casting of an ionic liquid film onto a random array of 7 μm diameter carbon microelectrodes (RAMTM electrode) followed by chronoamperometry, are employed. The ability of hydrophilic ions to partition from the water phase into the ionic liquid phase is unexpected and is shown to depend strongly on (i) the type of ion, (ii) specific interaction of the ion with the ionic liquid, and (iii) the concentration of the supporting electrolyte. Voltammetric responses obtained for the reduction of Fe(CN)63− partitioned into microdroplet and thin film deposits of MDIM+BF4− indicate selective uptake of ferricyanide into the ionic liquid phase. Chronoamperometric experiments at RAMTM electrodes are used to quantify both the concentration of Fe(CN)63− in the ionic liquid and the diffusion coefficient.

Carbonylation of alkynols catalyzed by Pd(II)/2-PyPPh2 dissolved in organic solvents and in ionic liquids: a facile entry to α-methylene γ- and δ-lactones

Abstract The carbonylation of terminal 3-alkyn-1-ols and 1-alkyn-4-ols by Pd(OAc) 2 associated with 2-(diphenylphosphino)pyridine (2-PyPPh 2 ) dissolved in organic solvents or in 1- n -butyl-3-methyl imidazolium ionic liquids affords quantitatively and selectively exo -α-methylene γ- and δ-lactones, respectively. In the case of the reactions performed in ionic liquids (biphasic conditions), the lactones were isolated by simple distillation and the ionic catalyst solution can be reused.

Electrochemical Behavior of Vitreous Glass Carbon and Platinum Electrodes in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Trifluoroacetate

The 1-n-butyl-3-methylimidazolium trifluoroacetate ionic liquid electrochemical windows have been investigated at vitreous carbon and platinum disc electrodes under static and dynamic conditions. The electrochemical window abruptly decreases by changing vitreous carbon (4.50 V) by platinum electrode (2.50 V). Electrode rotation and potential sweep rate did not affect the current-potential profiles but alter the current values of both anodic and cathodic peaks. The adsorption of imidazolium cation involved in the charge transfer process during the cathodic sweep rate was evidenced, mainly at low electrode rotation.

Tandem isomerisation-metathesis catalytic processes of linear olefins in ionic liquid biphasic system.

trans-3-Hexene is converted to heavier linear olefins by a tandem Ru-catalysed biphasic isomerisation/metathesis sequence. The difference in olefin metathesis and isomerisation rates is modulated by keeping the ionophilic metathesis catalyst in an ionic phase whilst the isomerisation catalyst is in another organic non-polar phase.

LÍQUIDOS IÔNICOS CONTENDO O CÁTION DIALQUILIMIDAZÓLIO: ESTRUTURA, PROPRIEDADES FÍSICO-QUÍMICAS E COMPORTAMENTO EM SOLUÇÃO

Ionic liquids, in specially those based on the 1,3-dialkylimidazolium cation, have been receiving special attention in differents areas due to their interesting physical-chemical properties. In this work, some aspects of their structure (in both solid and liquid state) and its relationships with their properties are reviewed.

Selective hydrogenation of 1,3-butadiene by transition metal compounds immobilized in 1-butyl-3-methyl imidazolium room temperature ionic liquids

Os complexos [Co(acac) 2 ], [Co(acac) 3 ], [Fe(acac) 3 ] e [Ni(acac) 2 ] (acac = acetilacetonato) dissolvidos em tetrafluoroborato de 1-butil-3-metilimidazonio (1), trifluorometanosulfonato de 1butil-3-metilimidazolio (2) ou hexafluorofosfato de 1-butil-3-metilimidazolio (3), catalisam a hidrogenacao de 1,3-butadieno em butenos em sistema catalitico tipicamente bifasico. A conversao do 1,3-butadieno, a seletividade e a frequencia de rotacao (TOF) sao fortemente dependentes do metal de transicao e do liquido ionico. Para [Co(acac) 2 ] dissolvido em 1, estudos cineticos sugerem que a reacao ocorre no meio liquido ionico, com uma energia aparente de ativacao de of 33.8 kJ mol -1 . A solucao ionica do catalisador pode ser recuperada e reutilizada varias vezes sem mudancas perceptiveis na atividade e seletividade da reacao. The compounds [Co(acac) 2 ], [Co(acac) 3 ], [Fe(acac) 3 ] and [Ni(acac) 2 ] (acac = acetylacetonate) dissolved in 1-butyl-3-methyl imidazolium tetrafluoroborate (1), trifluoromethanesulphonate (2) or hexafluorophosphate (3) catalyze the reduction of 1,3-butadiene into butenes in a typical two-phase catalytic reaction. The 1,3-butadiene conversion, the selectivity and turnover frequencies (TOF) are strongly dependent on the nature of the transition metal catalyst precursor and the ionic liquid. For [Co(acac) 2 ] dissolved in 1, kinetic studies strongly suggest that the reaction takes place in the ionic solution bulk, having an apparent activation energy for the overall process of 33.8 kJ mol -1 . The recovered ionic catalyst solution can be reused several times without any significant changes on activity and selectivity.

Palladium metal nanoparticles stabilized by ionophilic ligands in ionic liquids: synthesis and application in hydrogenation reactions

The reduction of [Pd(acac)(COD)]BF4 (acac = acetylacetonate; COD = 1,5-cyclooctadiene), dissolved in BMI·BF4, in the presence of P- or N-containing ionophilic ligands by H2 yields “soluble” and stable [Pd(0)]n nanoparticles (NPs). These ionic liquid soluble NPs are active and selective catalysts for the hydrogenation of 1,3-dienes and alkynes under mild reaction conditions. Selectivities up to 87% to cis-2-pentene and 95% conversion were obtained using Pd NPs modified with 1-(3-(diphenylphosphino)propyl)-2,3-dimethyl-1H-imidazol-3-ium N-bis(trifluoromethylsulfonyl)imide in 1-n-butyl-3-methylimidazolium tetrafluoroborate.

A palladium complex containing a new C2-symmetric bidentate non-racemic oxalamidine ligand: synthesis and catalytic properties

Abstract Non-racemic (S,S,S,S)-(-)-2,2′-bis-(4,5-diphenyl-1, 3-imidazoline) 1 has been prepared in good yields from the reaction of (S,S)-(-)1,2-diphenylethylenediamine with diethyl oxalimidate. The reaction of 1 with sodium tetrachloropalladate yields [ PdCl 2 ( 1 )] complex 2, whose structure has been ascertained by means of X-ray diffraction analysis. Complex 2 catalyzes the hydro-arylation of norbornene in good catalytic activity but with poor enantioselectivity.