Nuclear magnetic resonance studies on the rotational and translational motions of ionic liquids composed of 1-ethyl-3-methylimidazolium cation and bis(trifluoromethanesulfonyl)amide and bis(fluorosulfonyl)amide anions and their binary systems including lithium salts

Room temperature ionic liquids (ILs) are stable liquids composed of anions and cations. 1-ethyl-3-methyl-imidazolium (EMIm, EMI) is a popular and important cation that produces thermally stable ILs with various anions. In this study two amide-type anions, bis(trifluoro-methanesulfonyl)amide [N(SO(2)CF(3))(2), TFSA, TFSI, NTf(2), or Tf(2)N] and bis(fluorosulfonyl)amide [(N(SO(2)F)(2), FSA, or FSI] were investigated by multinuclear NMR spectroscopy. In addition to EMIm-TFSA and EMIm-FSA, lithium-salt-doped binary systems were prepared (EMIm-TFSA-Li and EMIm-FSA-Li). The spin-lattice relaxation times (T(1)) were measured by (1)H, (19)F, and (7)Li NMR spectroscopy and the correlation times of (1)H NMR, τ(c)(EMIm) (8 × 10(-10) to 3 × 10(-11) s) for the librational molecular motion of EMIm and those of (7)Li NMR, τ(c)(Li) (5 × 10(-9) to 2 × 10(-10) s) for a lithium jump were evaluated in the temperature range between 253 and 353 K. We found that the bulk viscosity (η) versus τ(c)(EMIm) and cation diffusion coefficient D(EMIm) versus the rate 1/τ(c)(EMIm) have good relationships. Similarly, linear relations were obtained for the η versus τ(c)(Li) and the lithium diffusion coefficient D(Li) versus the rate 1∕τ(c)(Li). The mean one-jump distances of Li were calculated from τ(c)(Li) and D(Li). The experimental values for the diffusion coefficients, ionic conductivity, viscosity, and density in our previous paper were analyzed by the Stokes-Einstein, Nernst-Einstein, and Stokes-Einstein-Debye equations for the neat and binary ILs to clarify the physicochemical properties and mobility of individual ions. The deviations from the classical equations are discussed.     

Unexpected decomposition of the bis (trifluoromethylsulfonyl) amide anion during electrochemical copper oxidation in an ionic liquid

In this letter we report on the decomposition of the bis (trifluoromethylsulfonyl) amide (TFSA) anion under quite mild electrochemical conditions. The results show clearly that the TFSA anion can easily be decomposed during anodic oxidation of copper in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) amide [BMP] TFSA at 70 °C leading to the formation of CuF₂. At room temperature, however, no significant decomposition was obtained. Therefore, one has to be very careful in applying ionic liquids based on TFSA anions under anodic conditions at elevated temperature as the TFSA anion might decompose, depending on the anode material.     

Preparation, properties, and crystal structures of organometallic ionic liquids comprising 1-ferrocenyl-3-alkylimidazolium-based salts of bis(trifluoromethanesulfonyl)amide and hexafluorophosphate

Bis(trifluoromethanesulfonyl)amide (TFSA), hexafluorophosphate (PF(6)(-)), and iodide salts of 1-ferrocenyl-3-alkylimidazolium were prepared and their thermal and physical properties, including the dependence on alkyl chain length (methyl-hexadecyl), were investigated. The TFSA salts were highly viscous ionic liquids with melting points around room temperature. 1-Ferrocenyl-4-methyltriazolium salts were also prepared for comparison. The ferrocenylimidazolium and ferrocenyltriazolium cations showed redox waves for both the ferrocenyl moiety and the azolium moiety and exhibited corresponding charge-transfer bands at around 330 nm, which were analyzed using the Marcus-Hush model. Crystal structure determinations at low temperature revealed that the PF(6) and iodide salts form layerlike structures composed of ionic layers of the charged moieties. The TFSA salt exhibited short hydrogen-bond-like intermolecular contacts between the hydrogen atoms of the cation and oxygen atoms of the anion.     

Thermal analysis of kerosene with 1,2-methyl ethyl 1-methyl pyrrolidinium bis(trifluoromethanesulfonyl) amide as an additive

This paper reports the thermal characterization of kerosene fuel-doped ionic liquid (1, 2-methylethyl 1-methyl pyrrolidinium bis(trifluoromethanesulfonyl) amide) (MEMP TFSA), an antistatic additive used in jet fuel engines. The ionic liquids (ILs) samples are prepared with the mass of 5, 10 and 15% in the kerosene fuel. These fuel samples are subjected to thermal decomposition studies at different scanning rates of 5, 10 and 15 °C min^?1 using the differential scanning calorimetry (DSC) method. The onset temperatures of exothermic reactions of kerosene-doped ILs are increased from 360–465 °C, when the mass percentage of ILs increased in the kerosene fuel. The boiling point of the kerosene-doped ILs was displaced to the higher temperature when compared to the pure kerosene. This showed that the doping of antistatic additives of ILs with kerosene increased its thermal stability property than the pure kerosene fuel. The thermo-kinetic studies are also carried out using Ozawa’s Kinetic method to determine the activation energy (E_a) and pre-exponential factor (A). The FTIR analysis showed that the kerosene-doped ionic liquid forms a homogenous mixture rather than prevailing separately.

     

Triethylammonium bis(tetrafluoromethylsulfonyl)amide protic ionic liquid as an electrolyte for electrical double-layer capacitors

This study describes the preparation, characterization and application of [Et(3)NH][TFSA], either neat or mixed with acetonitrile, as an electrolyte for supercapacitors. Thermal and transport properties were evaluated for the neat [Et(3)NH][TFSA], and the temperature dependence of viscosity and conductivity can be described by the VTF equation. The evolution of conductivity with the addition of acetonitrile rendered it possible to determine the optimal mixture at 25 °C, with a weight fraction of acetonitrile of 0.5. This mixture was also evaluated for transport properties, and showed a Newtonian behavior, as the neat PIL. An electrochemical study demonstrated, at first, a passivation on Al after the second cyclic voltammogram. Subsequently, the electrochemical window was estimated using a three-electrode cell to 4 V on a platinum electrode, and to 2.5 V on activated carbon. Finally, the neat PIL was found to exhibit good performances as promising electrolyte for supercapacitor applications.     

7Li NMR studies on complexation reactions of lithium ion with cryptand C211 in ionic liquids: comparison with corresponding reactions in nonaqueous solvents

(7)Li NMR spectra of DEME-TFSA [DEME=N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium; TFSA=bis(trifluoromethanesulfonyl)amide], EMI-TFSA (EMI=1-ethyl-3-methylimidazolium), MPP-TFSA (MPP = N-methyl-N-propylpyridinium), DEME-PFSA [PFSA=bis(pentafluoroethanesulfonyl)amide], and DEME-HFSA [HFSA=bis(heptafluoropropanesulfonyl)amide] ionic liquid (IL) solutions containing LiX (X=TFSA, PFSA, or HFSA) and C211 (4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane) were measured at various temperatures. As a result, it was found that the uncomplexed Li(I) species existing as [Li(X)(2)](-) in the present ILs exchange with the complexed Li(I) ([Li·C211](+)) and that the exchange reactions proceed through the bimolecular mechanism, [Li·C211](+) + [*Li(X)(2)](-)=[*Li·C211](+) + [Li(X)(2)](-). Kinetic parameters [k(s)/(kg m(-1) s(-1)) at 25 °C, ΔH(++)/(kJ mol(-1)), ΔS(++)/(J K(-1) mol(-1))] are as follows: 5.57×10(-2), 69.8 ± 0.4, and -34.9 ± 1.0 for the DEME-TFSA system; 5.77×10(-2), 70.6 ± 0.2, and -31.9 ± 0.6 for the EMI-TFSA system, 6.13×10(-2), 69.0 ± 0.3, and -36.7 ± 0.7 for the MPP-TFSA system; 1.35 × 10(-1), 65.2 ± 0.5, and -43.1 ± 1.4 for the DEME-PFSA system; 1.14×10(-1), 64.4 ± 0.3, and -47.1 ± 0.6 for the DEME-HFSA system. To compare these kinetic data with those in conventional nonaqueous solvents, the exchange reactions of Li(I) between [Li·C211](+) and solvated Li(I) in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were also examined. These Li(I) exchange reactions were found to be independent of the concentrations of the solvated Li(I) and hence proposed to proceed through the dissociative mechanism. Kinetic parameters [k(s)/s(-1) at 25 °C, ΔH(++)/(kJ mol(-1)), ΔS(++)/(J K(-1) mol(-1))] are as follows: 1.10 × 10(-2), 68.9 ± 0.2, and -51.3 ± 0.4 for the DMF system; 1.13×10(-2), 76.3 ± 0.3, and -26.3 ± 0.8 for the DMSO system. The differences in reactivities between ILs and nonaqueous solvents were proposed to be attributed to those in the chemical forms of the uncomplexed Li(I) species, i.e., the negatively charged species ([Li(X)(2)](-)) in ILs, and the positively charged ones ([Li(solvent)(n)](+)) in nonaqueous solvents.     

Ionic liquids based on diethylmethyl(2-methoxyethyl)ammonium cations and bis(perfluoroalkanesulfonyl)amide anions: influence of anion structure on liquid properties

A series of diethylmethyl(2-methoxyethyl)ammonium (DEME)-based ionic liquids were prepared using bis(perfluoroalkanesulfonyl)amide (C(n)F(2n+1)SO(2))(2)N anions with different perfluoroalkyl chain lengths (n = 0, 1, 2, 3, and 4), and the influence of the structural variation on their thermal, ion-diffusive (ionic conductivity and viscosity), ion-concentration (molar concentration and ion association), and solvatochromic (polarity and hydrogen-bond acceptor ability) properties was investigated. The elongation of the perfluoroalkyl chain causes the pronounced suppression of ionic conductivity, fluidity, and polarity. According to the crystallographic study of the corresponding (C(n)F(2n+1)SO(2))(2)N salts formed with high-symmetrical tetramethylammonium cations, the decreased ion diffusivity must be a consequence of the increased contribution of the interionic van der Waals interactions of FF type and hydrogen-bonding interactions of C-HF type in addition to C-HO type. The Kamlet-Taft π*-scale (polarity) is under the control of the ion concentration, associated with the perfluoroalkyl chain length in the anions. The larger Kamlet-Taft β-scale (hydrogen-bond acceptor ability) of DEME-based ionic liquids with a longer perfluoroalkyl chain appears to be responsible for the larger degree of ion association of oppositely charged ions, which was manifested in the Walden rule deviation.     

Effects of polyethylene spacer length in polymeric electrolytes on gelation of ionic liquids and ionogel properties

Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH₂)_m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 249–255     

Effect of water and organic solvents on the ionic dissociation of ionic liquids

The effect of water and several organic solvents on the density, viscosity, and conductivity of ionic liquids (ILs) 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and 1-n-butyl-3-methylimidazolium trifluoroacetate ([bmim][CF3CO2]) was studied at 298.15 K in wide composition ranges. The density, viscosity, and conductivity of the three neat ILs were also determined at various temperatures. Upon the basis of the molar conductivity of the mixtures and that of the neat ILs of the same viscosity, the degree of dissociation of ILs in the solutions was investigated. It can be deduced that the organic solvents enhance the ionic association of the ILs, the effect depending on the solvent dielectric constant, while water promotes dissociation significantly due to its high dielectric constant and its ability to form strong hydrogen bonds with the anions of the ILs.     

Corrosion of Ni in 1-butyl-1-methyl-pyrrolidinium bis (trifluoromethylsulfonyl) amide room-temperature ionic liquid: an in situ X-ray imaging and spectromicroscopy study

This paper reports a pioneering application of soft X-ray scanning transmission microscopy (STXM), combined with micro-spot X-ray absorption spectroscopy (XAS) and X-ray fluorescence spectroscopy (XRF), for the investigation of the corrosion of metal electrodes in contact with room-temperature ionic liquids (RTIL). Using an open electrochemical cell in vacuo we explore some fundamental aspects of the aggressiveness of the 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP][TFSA]) RTIL towards Ni under in situ electrochemical polarisation. The possibility of imaging electrochemically-induced morphological features in conjunction with micro-XAS and XRF spectroscopies has provided unprecedented details regarding the space distribution and chemical state of corrosion products.     

Ionic liquids and oligomer electrolytes based on the B(CN)4(-) anion; ion association, physical and electrochemical properties

The role of B(CN)(4)(-) (Bison) as a component of battery electrolytes is addressed by investigating the ionic conductivity and phase behaviour of ionic liquids (ILs), ion association mechanisms, and the electrochemical stability and cycling properties of LiBison based electrochemical cells. For C(4)mpyrBison and C(2)mimBison ILs, and mixtures thereof, high ionic conductivities (3.4 ≤σ(ion)≤ 18 mS cm(-1)) are measured, which together with the glass transition temperatures (-80 ≤T(g)≤-76 °C) are found to shift systematically for most compositions. Unfortunately, poor solubility of LiBison in these ILs hinders their use as solvents for lithium salts, although good NaBison solubility offers an alternative application in Na(+) conducting electrolytes. The poor IL solubility of LiBison is predicted to be a result of a preferred monodentate ion association, according to first principles modelling, supported by Raman spectroscopy. The solubility is much improved in strongly Li(+) coordinating oligomers, for example polyethylene glycol dimethyl ether (PEGDME), with the practical performance tested in electrochemical cells. The electrolyte is found to be stable in Li/LiFePO(4) coin cells up to 4 V vs. Li and shows promising cycling performance, with a capacity retention of 99% over 22 cycles.     

Introduction of an Ionic Liquid into the Micropores of a Metal–Organic Framework and Its Anomalous Phase Behavior

Controlling the dynamics of ionic liquids (ILs) is a significant issue for widespread use. Metal–organic frameworks (MOFs) are ideal host materials for ILs because of their small micropores and tunable host–guest interactions. Herein, we demonstrate the first example of an IL incorporated within the micropores of a MOF. The system studied consisted of EMI‐TFSA (1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF‐8 (composed of Zn(MeIM)₂; H(MeIM)=2‐methylimidazole) as the IL and MOF, respectively. Construction of the EMI‐TFSA in ZIF‐8 was confirmed by X‐ray powder diffraction, nitrogen gas adsorption, and infrared absorption spectroscopy. Differential scanning calorimetry and solid‐state NMR measurements showed that the EMI‐TFSA inside the micropores demonstrated no freezing transition down to 123 K, whereas bulk EMI‐TFSA froze at 231 K. Such anomalous phase behavior originates from the nanosize effect of the MOF on the IL. This result provides a novel strategy for stabilizing the liquid phase of the ILs down to a lower temperature region.     

Li+ cation environment, transport, and mechanical properties of the LiTFSI doped N-methyl-N-alkylpyrrolidinium+TFSI- ionic liquids

Molecular dynamics (MD) simulations have been performed on N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (mppy(+)TFSI(-)) and N,N-dimethyl- pyrrolidinium bis(trifluoromethanesulfonyl)imide (mmpy(+)TFSI(+)) ionic liquids (ILs) doped with 0.25 mol fraction LiTFSI salt at 303-500 K. The liquid density, ion self-diffusion coefficients, and conductivity predicted by MD simulations were found to be in good agreement with experimental data, where available. MD simulations reveal that the Li(+) environment is similar in mppy(+)TFSI(-) and mmpy(+)TFSI(+) ILs doped with LiTFSI. The Li(+) cations were found to be coordinated on average by slightly less than four oxygen atoms with each oxygen atom being contributed by a different TFSI(-) anion. Significant lithium aggregation by sharing up to three TFSI(-) anions bridging two lithiums was observed, particularly at lower temperatures where the lithium aggregates were found to be stable for tens of nanoseconds. Polarization of TFSI(-) anions is largely responsible for the formation of such lithium aggregates. Li(+) transport was found to occur primarily by exchange of TFSI(-) anions in the first coordination shell with a smaller (approximately 30%) contribution also due to Li(+) cations diffusing together with their first coordination shell. In both ILs, ion self-diffusion coefficients followed the order Li(+) < TFSI(-) < mmpy(+) or mppy(+) with all ion diffusion in mmpy(+)TFSI(-) being systematically slower than that in mppy(+)TFSI(-). Conductivity due to the Li(+) cation in LiTFSI doped mppy(+)TFSI(-) IL was found to be greater than that for a model poly(ethylene oxide)(PEO)/LiTFSI polymer electrolyte but significantly lower than that for an ethylene carbonate/LiTFSI liquid electrolyte. Finally, the time-dependent shear modulus for the LiTFSI doped ILs was found to be similar to that for a model poly(ethylene oxide)(PEO)/LiTFSI polymer electrolyte on the subnanosecond time scale.     

Metallosupramolecular chemistry with bis(benzene-o-dithiolato) ligands

The bis(benzene-o-dithiol) ligands H(4)-1, H(4)-2, and H(4)-3 react with [Ti(OC(2)H(5))(4)] to give dinuclear triple-stranded helicates [Ti(2)L(3)](4)(-) (L = 1(4)(-), 2(4)(-), 3(4)(-)). NMR spectroscopic investigations revealed that the complex anions possess C(3) symmetry in solution. A crystal structure analysis for (PNP)(4)[Ti(2)(2)(3)] ((PNP)(4)[14]) confirmed the C(3) symmetry for the complex anion in the solid state. The complex anion in Li(PNP)(3)[Ti(2)(1)(3)] (Li(PNP)(3)[13]) does not exhibit C(3) symmetry in the solid state due to the formation of polymeric chains of lithium bridged complex anions. Complexes [13](4)(-) and [14](4)(-) were obtained as racemic mixtures of the Delta,Delta and Lambda,Lambda isomers. In contrast to that, complex (PNP)(4)[Ti(2)(3)(3)] ((PNP)(4)[15]) with the enantiomerically pure chiral ligand 3(4)(-) shows a strong Cotton effect in the CD spectrum, indicating that the chirality of the ligands leads to the formation of chiral metal centers. The o-phenylene diamine bridged bis(benzene-o-dithiol) ligand H(4)-4 reacts with Ti(4+) to give the dinuclear double-stranded complex Li(2)[Ti(2)(4)(2)(mu-OCH(3))(2)] containing two bridging methoxy ligands between the metal centers. The crystal structure analysis and the (1)H NMR spectrum of (Ph(4)As)(2)[Ti(2)(4)(2)(mu-OCH(3))(2)] ((Ph(4)As)(2)[(16]) reveal C(2) symmetry for the anion [Ti(2)(4)(2)(mu-OCH(3))(2)](2)(-). For a comparative study the dicatechol ligand H(4)-5, containing the same o-phenylene diamine bridging group as the bis(benzene-o-dithiol) ligands H(4)-4, was prepared and reacted with [TiO(acac)(2)] to give the dinuclear complex anion [Ti(2)(5)(2)(mu-OCH(3))(2)](2)(-). The molecular structure of (PNP)(2)[Ti(2)(5)(2)(mu-OCH(3))(2)] ((PNP)(2)[17]) contains a complex anion which is similar to [16](2)(-), with the exception that strong N-H...O hydrogen bonds are formed in complex anion [17](2)(-), while N-H...S hydrogen bonds are absent in complex anion [16](2)(-).     

Oxidative-stability enhancement and charge transport mechanism in glyme-lithium salt equimolar complexes

The oxidative stability of glyme molecules is enhanced by the complex formation with alkali metal cations. Clear liquid can be obtained by simply mixing glyme (triglyme or tetraglyme) with lithium bis(trifluoromethylsulfonyl)amide (Li[TFSA]) in a molar ratio of 1:1. The equimolar complex [Li(triglyme or tetraglyme)(1)][TFSA] maintains a stable liquid state over a wide temperature range and can be regarded as a room-temperature ionic liquid consisting of a [Li(glyme)(1)](+) complex cation and a [TFSA](-) anion, exhibiting high self-dissociativity (ionicity) at room temperature. The electrochemical oxidation of [Li(glyme)(1)][TFSA] takes place at the electrode potential of ~5 V vs Li/Li(+), while the oxidation of solutions containing excess glyme molecules ([Li(glyme)(x)][TFSA], x > 1) occurs at around 4 V vs Li/Li(+). This enhancement of oxidative stability is due to the donation of lone pairs of ether oxygen atoms to the Li(+) cation, resulting in the highest occupied molecular orbital (HOMO) energy level lowering of a glyme molecule, which is confirmed by ab initio molecular orbital calculations. The solvation state of a Li(+) cation and ion conduction mechanism in the [Li(glyme)(x)][TFSA] solutions is elucidated by means of nuclear magnetic resonance (NMR) and electrochemical methods. The experimental results strongly suggest that Li(+) cation conduction in the equimolar complex takes place by the migration of [Li(glyme)(1)](+) cations, whereas the ligand exchange mechanism is overlapped when interfacial electrochemical reactions of [Li(glyme)(1)](+) cations occur. The ligand exchange conduction mode is typically seen in a lithium battery with a configuration of [Li anode|[Li(glyme)(1)][TFSA]|LiCoO(2) cathode] when the discharge reaction of a LiCoO(2) cathode, that is, desolvation of [Li(glyme)(1)](+) and insertion of the resultant Li(+) into the cathode, occurs at the electrode-electrolyte interface. The battery can be operated for more than 200 charge-discharge cycles in the cell voltage range of 3.0-4.2 V, regardless of the use of ether-based electrolyte, because the ligand exchange rate is much faster than the electrode reaction rate.     

Iron(II) cage complexes of N-heterocyclic amide and bis(trimethylsilyl)amide ligands: synthesis, structure, and magnetic properties

Metallation of hexahydropyrimidopyrimidine (hppH) by [Fe{N(SiMe(3))(2)}(2)] (1) produces the trimetallic iron(II) amide cage complex [{(Me(3)Si)(2)NFe}(2)(hpp)(4)Fe] (2), which contains three iron(II) centers, each of which resides in a distorted tetrahedral environment. An alternative, one-pot route that avoids use of the highly air-sensitive complex 1 is described for the synthesis of the iron(II)-lithium complex [{(Me(3)Si)(2)N}(2)Fe{Li(bta)}](2) (3) (where btaH = benzotriazole), in which both iron(II) centers reside in 3-coordinated pyramidal environments. The structure of 3 is also interpreted in terms of the ring laddering principle developed for alkali metal amides. Magnetic susceptibility measurements reveal that both compounds display very weak antiferromagnetic exchange between the iron(II) centers, and that the iron(II) centers in 2 and 3 possess large negative axial zero-field splittings.     

From the tetra(amino) phosphonium cation, [P(NHPh)4]+, to the tetra(imino) phosphate trianion, [P(NPh)4]3-, two-faced ligands that bind anions and cations

The tetraanilino phosphonium cation, [P(N(H)Ph)4]+, 1+, is sequentially deprotonated by Bu(n)Li in thf. The deprotonation reaction of the chloride derivative, Cl, was monitored by (31)P NMR, which revealed the successive formation of the neutral [P(N(H)Ph)3(NPh)], 2, the monoanionic [P(N(H)Ph)2(NPh)2]-, 3-, the dianionic [P(N(H)Ph)(NPh)3]2-, 4(2-), and finally the trianionic species [P(NPh)(4)](3-), (3-). Considering the isoelectronic relationship of oxo, =O, and imino groups, =NR, as well as hydroxy, -OH, and amino groups, -N(H)R, the neutral complex corresponds to phosphoric acid, H3PO4, whereas the anions 3-, 4(2-) and 5(3-) are analogues of dihydrogen phosphate, H2PO4-, monohydrogenphosphate, HPO4(2-), and orthophosphate ions, PO4(3-), respectively. Solid state structures were obtained of 1Cl, 2LiCl(thf)(2), 3Li(thf)(3.5), 3Li(2)Cl(thf)(4.25), 3Li(2)Cl(thf)(6) and 5Li(4)Cl(thf)(4). All systems provide two separate N-P-N chelation sites at opposite ligand faces, either consisting of the di(amino) arrangement P(NH)(2), acting as a double H-bond donor, the di(imino) arrangement PN(2), donating two electron pairs, or the mixed amino imino arrangement P(N)(NH), which supplies both electron pair and H-donor site. Interesting in this aspect is the mixed amino imino derivative 3- which has the ability to chelate a Lewis acid, such as a metal ion, at one face and a Lewis base, such as an anionic or neutral donor at the opposite ligand face. The formation of 1-D aggregates and the entrapment of lithium chloride are key characteristics of the supramolecular structures of the discussed complexes.     

Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene

A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).     

Cage lifetimes of ionic liquids as studied by the magnetic field effect probe

Magnetic field effects (MFEs) on the photoinduced hydrogen abstraction reaction of benzophenone with phenol were investigated in ionic liquids (ILs) with a short alkyl chain (N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide (TMPA TFSA)) and long alkyl chains ((N,N,N-trimethyl-N-octylammonium bis(trifluoromethanesulfonyl)amide (TMOA TFSA) and N-decyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl)amide (DTMA TFSA)) by a nanosecond laser flash photolysis technique. In each ionic liquid, escaped radical yield of a benzophenone ketyl radical rapidly increased with increasing magnetic field strength (B) of 0 T < B≤ 0.01 T. At 0.01 T < B≤ 0.4 T, the escaped radical yield almost saturated in TMPA TFSA or gradually increased in TMOA TFSA and DTMA TFSA. At much higher fields of 0.4 T < B≤ 30 T, the yield gradually decreased, resulting in 10-15% decrease at 30 T. The observed MFEs can be explained by the hyperfine coupling and Δg mechanisms together with the relaxation mechanism. On the time profiles of the transient absorption observed for the benzophenone ketyl radical, MFEs were generated in the time range of 0 < t < 0.6 μs. The cage lifetimes of TMOA TFSA and DTMA TFSA were estimated to be at least 120 ns.