Amide Salts Research Articles

Synthesis and Characterization of Pyrazolyl‐Functionalized Imidazolium‐Based Ionic Liquids and Hemilabile (Carbene)palladium(II) Complex Catalyzed Heck Reaction

AbstractNeat reactions of 1‐(pyrazolylmethyl)imidazole with an excess of alkyl or polyfluoroalkyl halides at 100 °C followed by subsequent metathetical reactions with LiN(SO2CF3)2 or KPF6 at 25 °C gave rise to a series of monoquaternary salts 3a–3k. These salts can be also prepared through treatment of 1‐alkylimidazole with 1‐(chloromethyl)pyrazole hydrochloride in the presence of base, followed by anion exchange with LiN(SO2CF3)2 or KPF6. Their phase‐transition temperature, thermal stability, density and solubility in common solvents have been investigated. Most of the bis(trifluoromethanesulfon)amide salts are room‐temperature ionic liquids. The effect of anions and of alkyl substituents bonded to the imidazolium cation on the physicochemical properties was examined. Using 3‐butyl‐1‐(pyrazolylmethyl)imidazolium chloride (2d), the precursor of 3‐butyl‐1‐(pyrazolylmethyl)imidazolium bis(trifluoromethanesulfon)amide (3d), as a reactant, a hemilabile (N‐heterocyclic carbene)palladium(II) complex 4 was synthesized through a (carbene)silver(I) transfer reagent. It was characterized by single‐crystal X‐ray diffraction analysis. The catalytic activity and recyclability of 4 in 3d were preliminarily evaluated by consecutive Heck reactions using different substrates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Deactivation pathways of ethylene polymerization catalysts derived from titanium and zirconium 1,3-bis(furyl)-1,1,3,3-tetramethyldisilazide complexes

The stoichiometric reaction between the previously described lithium amide salts, LiN(SiMe2R)2 [Li{i}, R = furyl, Li{ii}, R = 2-methylfuryl] and titanium(iv)chloride at low temperature afforded the mono-amide compounds Ti{i}Cl3 (1a) and Ti{ii}Cl3 (1b). The analogous zirconium derivatives Zr{i}Cl3 (3a) and Zr{ii}Cl3 (3b) were accessed via the reaction of excess trimethylsilylchloride with the mixed tetra-amide species, Zr{i}(NMe2)3 (2a) and Zr{ii}(NMe2)3 (2b). The bis-amide complexes Ti{ii}2Cl2 (4b), Zr{i}2Cl2 (5a) and Zr{ii}2Cl2 (5b) were synthesized in a straightforward salt metathesis reaction employing two equivalents of Li{i} or Li{ii} with the metal salts, MCl4(THF)2. The reactivity of the halide compounds 1 and 3-5 with a variety of alkylating agents was studied, with ligand transfer from the transition-element to the main group metal-alkyl reagent being the predominant reaction pathway. The reaction of 4b with MeLi was, however, partially successful affording the titanium(III) complex, Ti{ii}2X (X = Cl/Me, 6b'); this compound was subsequently made as the pure chloride from the reaction of two equivalents of Li{iii} with TiCl3(THF)3. The targeted dialkyl species, Ti{ii}Me2 (7b), was successfully isolated from the reaction between the dichloride 4b and dimethylmagnesium. The molecular structures of 1a, 1b, [3a]2 [3b]2, 4b, 5b and 6b have been solved using single-crystal X-ray diffraction techniques, indicating varying nuclearity of the complexes and hapticities for the amide ligands in the solid-state. The catalytic activity of selected complexes in the polymerization of ethylene is reported.

Ionic Liquids Can Be Distilled After All

The widely held assumption that low-melting-point salts, known as ionic liquids, cannot be distilled because they have no measurable vapor pressure has been shown to be unfounded. An international team of researchers led by Luis P. N. Rebelo, professor of chemical and biological technology at the New University of Lisbon, in Portugal, has shown that many ionic liquids can be distilled at low pressure without decomposition ( Nature 2006, 439, 831). The research team demonstrated that selected families of ionic liquids, such as bis[(trifluoromethyl) sulfonyl]amide salts, can be vaporized under vacuum at 200-300 °C and then recondensed at lower temperatures. At lower temperatures, the ionic liquids exert undetectable pressure in the gas phase and will therefore keep their environmentally friendly status because they do not pollute the atmosphere, Rebelo tells C&EN. The team also distilled binary mixtures of ionic liquids and demonstrated significant enrichment of one component in the distillate and the oth...

Pyrazolyl-functionalized 2-methylimidazolium-based ionic liquids and their palladium(ii) complexes as recyclable catalysts

A series of pyrazolyl- and 3,5-dimethylpyrazolyl-functionalized 2-methylimidazolium-based salts have been prepared through neat reactions of 1-pyrazolylmethylene-2-methylimidazole and 1-(3,5-dimethylpyrazolylmethylene)-2-methylimidazole with alkyl or polyfluoroalkyl iodides or 1-bromohexane, followed by anion exchange with LiN(SO2CF3)2 or KPF6. Their thermal properties were determined by DSC and TGA. Most of the bis(trifluoromethanesulfonyl)amide salts are room temperature ionic liquids. The influence of anions and of the structural variation in the 2-methylimidazolium-based cations on the physicochemical properties is discussed. These salts reacted easily with palladium(II) chloride to generate mononuclear palladium ionic liquid complexes. The catalytic activity and recyclability of the palladium complexes in the corresponding ionic liquids were preliminarily examined using Heck, Suzuki and Sonogashira cross-coupling reactions in the absence of phosphine ligands.

Phosphazene-based ionic liquids: synthesis, temperature-dependent viscosity, and effect as additives in water lubrication of silicon nitride ceramics.

Phosphazene rings with (dimethylamino)ethoxy (1, 2), pyridylmethoxy (3), or (dimethylamino)propoxy (4) chains were synthesized and quaternized at the substitutent nitrogen by treatment with methyl iodide at 35 degrees C over 3-6 h to give polyiodo salts, 5-8. Subsequent metathesis with LiN(SO(2)CF(3))(2) or NaBF(4) gave the respective ionic salts, 9-13. The amide salts, 9-12, were viscous liquids with pour points at 55-100 degrees C, and the tetrafluoroborate salt, 13, was a solid, mp 168 degrees C. The compositions of 2 and 5-13 were confirmed by elemental analysis and spectroscopic methods. Compounds 1, 2, and 4 were viscous liquids (d(25) = 1.67 g cm(-3); eta(25) = 0.76-1.56 mPa s(-1) ) with pour points at approximately 15 degrees C. The solid polyquaternary salts, 5-8, melted at 130-194 degrees C. The ionic liquids, 9-12, had an average density of approximately 1.73 g cm(-3) at 25 degrees C, and viscosities (25 degrees C) ranged between 68.3 and 139.2 mPa s(-1). A plot of the viscosities of 9-12 vs temperature revealed an almost linear correlation between 55 and 120 degrees C. Friction and wear properties of water with 0.25 wt % of 9-12 as boundary lubricant additives were evaluated on Si(3)N(4)/Si(3)N(4) ceramic interfaces. The most significant observation is that they caused a decrease in the running-in period.

Quaternary salts containing the pentafluorosulfanyl (SF5) group.

The first quaternary salts of pyridine (2), N-methyl imidazole (3), N-propyl triazole (4), and pyridazine (5) that contain the pentafluorosulfanyl (SF(5)) group were prepared and characterized. Neat reactions of the aromatic nitrogen compounds with SF(5)(CF(2))(n)(CH(2))(m)I (n = 2 or 4, m = 2 or 4) gave quaternary iodides 6a-c, 7a-c, 8a, and 9a,b, which were metathesized with LiN(SO(2)CF(3))(2) to form the bis(trifluoromethylsulfonyl)amides 10a-c, 11a-c, 12a, and 13a,b, in high yields. With the exception of the pyridine bis(trifluoromethylsulfonyl)amide salts, the compounds melted or exhibited a T(g) at <0 degrees C. The methylimidazolium, pyridinium, and pyridazinium salts exhibited densities of approximately 2 g/cm(3). Particularly striking was the density of CF(3)(CF(2))(5)(CH(2))(2)-pyridazinium N(CF(3)SO(2))(2) measured at 2.13 g/cm(3); however, an atypically high density for the 1-CF(3)(CF(2))(5)(CH(2))(2)-3-methyl imidazolium amide (14) was also observed at 1.77 g/cm(3). All quaternary salts were characterized via IR, (19)F, (1)H, and (13)C NMR spectra and elemental analyses.

A new family of ionic liquids based on the 1-alkyl-2-methyl pyrrolinium cation

Five new salts based on 1-alkyl-2-methyl pyrrolinium ion are reported, two involving the iodide ion and three involving the bis(trifluoromethanesulfonyl) amide ion. The iodide salts have melting points around 100 °C, while the amide salts have melting points around room temperature. Two of the amide salts can be easily quenched into the glassy state and exhibit glass transition temperatures around −70 °C. The 2-methyl pyrrolinium cation bears structural similarities to the aromatic imidazolium cations on one hand and the cyclic ammonium cation family based on the pyrrolidinium cation on the other. The properties of the salts reported here are compared within these two related families of salts.

The effect of anion fluorination in ionic liquids—physical properties of a range of bis(methanesulfonyl)amide salts

The bis(trifluoromethanesulfonyl)amide, TFSA, anion is widely used in the genesis of room temperature ionic liquids as it is non-spherical, fluorinated and has a particularly diffuse charge. However, the extent to which each of these structural features is responsible for the low melting point, fluidity and excellent stability of the resultant ionic liquids has yet to be described. We present the synthesis and analysis of a range of analogous, non-fluorinated species containing the bis(methanesulfonyl)amide, NMes2−, ligand. Utilisation of this anion produces ionic liquids that are hydrophilic and extremely low melting, but with decreased thermal and electrical stability and significantly increased viscosity. The crystal structures of the dimethyl pyrrolidinium bis(methanesulfonyl)amide and TFSA species are compared, and the number of close contacts within each is assessed. Comparison of these structural and physical properties provides new insight into the effect of anion fluorination on these ionic liquids.

Microstructural and molecular level characterisation of plastic crystal phases of pyrrolidinium trifluoromethanesulfonyl salts

Ambient temperature conductive plastic crystal phases of alkylmethylpyrrolidinium trifluoromethanesulfonyl amide (TFSA) salts are studied using positron annihilation lifetime spectroscopy (PALS) to examine the role of vacancy size and concentration in conductivity. The ethyl methylpyrrolidinium TFSA salt (P 12 TFSA) has larger vacancies and a greater concentration of vacancies than the dimethylpyrrolidinium TFSA salt (P 11 TFSA) over the temperature range investigated. The relative vacancy size and concentration vary with temperature and reflect the solid–solid transitions as measured by differential scanning calorimetry (DSC). P 12 TFSA has greater conductivity than P 11 TFSA and has furthermore been observed to exhibit slip planes at room temperature. P 12 TFSA has greater entropy changes associated with solid–solid phase transitions below the melting point than P 11 TFSA possibly indicating greater rotational freedom in P 12 TFSA. These results support the notion that the diffusion, conduction, and plastic flow properties of the pyrrolidinium TFSA salts are derived from the lattice vacancies.

Synthesis and Late Transition Metal Complexes of the Heterofunctional Phosphaneo-Ph2PNHC6H4P(S)Ph2

The difunctional ligand o-Ph2PNHC6H4P(S)Ph2 (PS) has been prepared by treatment of the lithium amide salt of 2-(diphenylthiophosphanyl)aniline {2-[Ph2P(S)]C6H4NH2} with Ph2PCl. The new ligand was oxidised to give the mixed chalcogen species Ph2P(E)NHC6H4P(S)Ph2, by treatment with H2O2 (where E = O) or aerial oxidation by recrystallisation from MeOH, and by reaction with Se8 (where E = Se) in warm toluene. The complexes [MCl(η3-C3H5)(PS)] (M = Pt or Pd), cis-[PtCl2(PS)(PMe2Ph)], [(AuCl)(PS)], cis-[MCl2(PS)2] (M = Pt or Pd), cis-[PtMe2(PS)2] and trans-[PtMeCl(PS)2] have been synthesised by reaction of either [Pt(μ-Cl)(μ-η2:η1-C3H5)]4, [Pd(μ-Cl)(η3-C3H5)]2, [{PtCl(μ-Cl)(PMe2Ph)}2], [AuCl(tht)] (tht = tetrahydrothiophene), [PdCl2(cod)] or [PtX2(cod)] (X = Me or Cl; cod = cycloocta-1,5-diene) with (PS). In all these complexes the ligand (PS) is monodentate P-bound. Chloride abstraction from [MCl(η3-C3H5)(PS)] (M = Pt or Pd), cis-[PtCl2(PS)(PMe2Ph)], cis-[PtCl2(PS)2] and trans-[PtMeCl(PS)2], using Ag[ClO4], gave the monocationic [M(η3-C3H5)(PS)][ClO4] (M = Pt or Pd), cis-[PtCl(PS)(PMe2Ph)][ClO4], trans-[PtMe(PS)2][ClO4] or dicationic [Pt(PS)2][ClO4]2 compounds in which the ligand (PS) is κ2-P,S-bound. All compounds described here have been characterised by a combination of 31P{1H} and 1H NMR spectroscopy, microanalyses, FAB mass spectrometry and IR spectroscopy. The molecular structures of [AuCl(Ph2PNHC6H4P(S)Ph2-P)] in which there is an intramolecular hydrogen-bonding interaction between the amine proton and the sulfur atom of the thiophosphoryl group and trans-[Pt(Ph2PNHC6H4P(S)Ph2-κ2-P,S)2][ClO4]2·CH2Cl2·2H2O in which the perchlorate counterions are associated by hydrogen-bonding interactions to the amine protons of the κ2-P,S ligands have been determined by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Methanesulfonate and p-toluenesulfonate salts of the N-methyl-N-alkylpyrrolidinium and quaternary ammonium cations: novel low cost ionic liquids

The preparation and characterization of a series of novel salts, based on the N-methyl-N-alkylpyrrolidinium or quaternary ammonium organic cations coupled with sulfonate type anions, namely the mesylate (CH3SO3−) and tosylate (CH3C6H4SO3−) anions are reported. These salts are analogues of the previously described organic cation bis(trifluoromethanesulfonyl)amide (TFSA) salts that form useful ionic liquids of interest in “Green” synthesis. Several of the salts are liquid below 50 °C, e.g. tributylhexylammonium tosylate and ethylmethylpyrrolidinium mesylate and one is liquid at and below room temperature (tributylhexylammonium mesylate). These new salts have a cost advantage over salts of the TFSA−, PF6− and CF3SO3− anions. Electrochemical and thermal properties have been investigated. The salts are stable to beyond 100 °C and exhibit electrochemical potential windows of at least ±2 V vs. Ag/Ag+. Some of the salts exhibit multiple crystalline phases below their melting points, potentially indicative of plastic crystal behaviour, whilst others showed more simple solid–liquid behaviour. Many of the salts were found to be glass forming.

Formation of Heterodimer Complexes between Analogous Chiral Lithium Amides: NMR Spectroscopic and Computational Studies

Mixing two analogous lithium amide salts from methyl(1-phenyl-2-(pyrrolidin-1-yl)ethyl)[15N]amine (1) and (2-methoxy-1-phenylethyl)methylamine (2) in a 1:1 ratio in diethyl ether resulted in a form...

Two approaches to α,α-bis-Mannich salts of N-monosubstituted amides

Two generally applicable syntheses of 2-bis-(dimethylaminomethyl)acetamides 9 are described. The first one involves reaction of N-mono substituted acetamides 3 with dimethyl(methylene)ammonium chloride in the presence of phosphorus oxychloride using diethyl ether as a solvent. Starting from ketoximes, the amines 9 are obtained under the same reaction conditions via Beckmann rearrangement. C-Aminomethylation observed in all cases may be the result of the formation of imidoyl chlorides 5 as intermediates.

Efficient transformation of nitrile into amide under mild condition

Transformation of various kinds of nitriles into the corresponding amides or amide salts was performed in good yields by the addition of two equiv of chlorotrimethylsilane and two equiv of water at 0°C to 25°C. Graphic

Synthesis and Structure of the Bis(amido)sodate Salt Na[Na{N(SiMe3)2AlMe3}2]: An Na+ Ion Complexed Solely by Na+- - -H3C− Interactions

The synthesis and structural characterization of the sodium amide salt Na[Na{N(SiMe3)2AlMe3}2] are described. The structure is composed of an infinite array of bis(amido)sodate [Na{N(SiMe3)2AlMe3}2...

Reduction of Secondary Carboxamides to Imines.

This article reports in detail on the discovery that zirconium(IV) salts of secondary amides and lactams are transformed by Cp(2)ZrHCl to N-substituted imines in one step. The method represents the first controlled reduction of amides and lactams to the corresponding imines, a transformation that is otherwise very difficult to achieve because imines are reduced more rapidly than carboxamides by most metal hydride reagents. No products of reductive cleavage of the carboxamides are observed. Efforts to replace 2 mol equiv of Cp(2)ZrHCl with simpler, less costly alternatives led to the finding that a diisobutylaluminum enolate can be substituted for the initial zirconium enolate. Such aluminum amides are smoothly reduced to the corresponding imine using Cp(2)ZrHCl in good yield. Moreover, aluminum amides are also reduced to imines using either low-valent titanium species or triethylsilane. In these alternative procedures, use of Cp(2)ZrHCl is eliminated altogether in the title transformation.

What Do Ab Initio Calculations Predict for the Structure of Lithiated Azaenolates of Peptides?

AbstractStructures and conformations of the azaenolate lithium salts of amides (formamide, acetamide, and N‐methylacetamide) and of the dipeptide model N‐formylalaninamide were investigated by means of ab initio MO theory. Four possible structures of the lithiated C‐enolates of acetamide were also included in the study. All structures were calculated at the HF/6‐31+G(d) and MP2(fc)/6‐31 + G(d)/HF/6‐31 + G(d) levels; the lithiated azaenolates of formamide were also investigated at higher theoretical levels (up to MP4(fc)/6‐311 + G(d,p)/MP2(fc)/6‐311 + G(d,p)). For the lithiated azaenolates of all amides investigated, the most stable structure contains a four‐membered ring in which the lithium ion is complexed by the oxygen and nitrogen atoms; the substituents attached to the carbon and nitrogen atoms of the azaenolate are in a cis arrangement. The lithiated azaenolates of acetamide are predicted to be more stable than the corresponding C‐enolates. To simulate solvation, calculations on complexes of the lithiated azaenolates of formamide with up to three molecules dimethyl ether were also performed, and all azaenolates of amides were also reoptimized by ab initio reaction‐field calculations. Both solvation models reduce the preference for lithium‐chelated cis structures. The Ramachandran maps of the dilithiated bis(azaenolate) of N‐formylalaninamide (having cis or trans arrangements of the azaenolate substituents) were scanned by MNDO calculations for conformational accessible regions. Thirteen stable structures were subsequently optimized at the HF/6‐31 + G(d) ab initio level. The global minimum resembles a peptide in C7 conformation, but other conformations, not known for peptides, are close in energy. The structures of dimers of the lithiated azaenolates of N‐methylacetamide and of glycinaldehyde were also calculated. The NMR chemical shielding of carbon, nitrogen, and oxygen atoms in all structures were predicted ab initio by using the gauge‐including atomic orbital (GIAO) method.

Comparison of an Amide and Amine Salt as Friction Modifiers for a Magnetic Thin Film Medium©

The frictional properties of a novel lubricant on a thin film magnetic medium are presented. The novel carboxylic amine salt has better frictional characteristics than the corresponding amide. The microscopic coverage of the lubricant film on the magnetic medium also is investigated by means of FTIR. Coverage does not change during reciprocating motion for the amine salt, which tightly anchors to the surface, since the friction coefficient is low and steady. The friction coefficient of the amine salt decreases with increasing lubricant on the surfaces. In contrast for the amide, the rubbing contact process breaks the lubricant film and results in high friction coefficient, since the amide has weak interaction with the surfaces. The friction coefficient is almost independent of the amount of the lubricant for the amide.

Facile nucleophilic displacement on a 4-triazolylpyrimidine deoxynucleoside: single-step synthesis of N-acylated 5-methyldeoxycytidines

A 4-triazolyl substituted pyrimidine nucleoside undergoes nucleophilic displacement with the sodium salts of amides and thiols at room temperature in 1,4-dioxane exclusively at the 4-position to provide a simple and efficient preparation of 4-N-acylated and 4-thiolated analogues, respectively.

Reductive deoxygenation by Cp 2ZrHCl: Selective formation of imines via zirconation/hydrozirconation of amides

A general new process is described by which zirconium (IV) salts of secondary amides and lactams are transformed by Cp 2ZrHCl directly into N-substituted imines in one step.