Philipp Eiden

An Experimental and Theoretical Study of the Aluminium Species Present in Mixtures of AlCl3 with the Ionic Liquids [BMP]Tf2N and [EMIm]Tf2N

It is known that nano- or microcrystalline aluminium may be electrodeposited from mixtures of AlCl(3) and the ionic liquids 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP]Tf(2)N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf(2)N), and that two phases form with higher formal concentrations of AlCl(3) (at 1.6 mol L(-1) (x(Al)=0.33) and 2.5 mol L(-1) (x(Al)=0.39), respectively). This account analyzes the hitherto unknown molecular nature of these mixtures by a detailed experimental (multinuclear NMR and Raman spectroscopies) and theoretical study (BP86/TZVP DFT calculations, including COSMO solvation energies). The addition of AlCl(3) to the two liquids first leads to complexation with [Tf(2)N](-) and then disproportionation of the initial [AlCl(x)(Tf(2)N)(y)](-) complexes give Al(Tf(2)N)(3) and [AlCl(4)](-). At high concentrations of AlCl(3), the lower phase consists almost completely of Al(Tf(2)N)(3), whereas in the upper phase [AlCl(4)](-) is the dominant species. Electrodeposition of aluminium in the upper phase occurs from mixed AlCl(x)(Tf(2)N)(y) species, most likely from [AlCl(2)(Tf(2)N)(2)](-) formed in small concentrations at the phase boundary between the [AlCl(4)](-) and the Al(Tf(2)N)(3) layers. All the findings are supported by DFT calculations as well as an X-ray crystal structure determination of Al(Tf(2)N)(3). The latter was separated from the mixture by sublimation on a preparative scale. It was independently prepared from AlEt(3) and HNTf(2) and fully characterized. Moreover, the ionic liquids [BMP]AlCl(4) (m.p. 74 degrees C) and [EMIm]AlCl(4) (m.p. -7 degrees C), which mainly form the upper layer in the biphasic regime, were independently prepared and also fully characterized.

Temperature Dependence of the Viscosity and Conductivity of Mildly Functionalized and Non‐Functionalized [Tf2N]− Ionic Liquids

A series of bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) with classical as well as mildly functionalized cations was prepared and their viscosities and conductivities were determined as a function of the temperature. Both were analyzed with respect to Arrhenius, Litovitz and Vogel-Fulcher-Tammann (VFT) behaviors, as well as in the context of their molecular volume (V(m)). Their viscosity and conductivity are highly correlated with V(m)/T or related expressions (R(2) ≥0.94). With the knowledge of V(m) of new cations, these correlations allow the temperature-dependent prediction of the viscosity and conductivity of hitherto unknown, non- or mildly functionalized ILs with low error bars (0.05 and 0.04 log units, respectively). The influence of the cation structure and mild functionalization on the physical properties was studied with systematically altered cations, in which V(m) remained similar. The T(o) parameter obtained from the VFT fits was compared to the experimental glass temperature (T(g)) and the T(g)/T(o) ratio for each IL was calculated using both experimental values and Angells relationship. With Walden plots we investigated the IL ionicity and interpreted it in relation to the cation effects on the physical IL properties. We checked the validity of these V(m)/T relations by also including the recently published variable temperature viscosity and conductivity data of the [Al(OR(F))(4)](-) ILs with R(F) =C(H)(CF(3))(2) (error bars for the prediction: 0.09 and 0.10 log units, respectively).

In Silico Predictions of the Temperature-Dependent Viscosities and Electrical Conductivities of Functionalized and Nonfunctionalized Ionic Liquids

The viscosity (η) and electrical conductivity (κ) of ionic liquids are, next to the melting point, the two key properties of general interest. The knowledge of temperature-dependent η and κ data before their first synthesis would permit a much more target-oriented development of ionic liquids. We present in this work a novel approach to predict the viscosity and electrical conductivity of an ionic liquid without further input of experimental data. For the viscosity, only some basic physical observables like the Gibbs solvation energy (ΔG(solv)(*,∞)), which was calculated at the affordable DFT-level (RI-)BP86/TZVP/COSMO, the molecular radius, calculated from the molecular volume V(m) of the ion volumes, and the symmetry number (σ), according to group theory, are necessary as input. The temperature dependency (253-373 K) of the viscosity (4-19000 mPa s) was modeled by an Arrhenius approach. An alternative way, which avoids the deficits of the Arrhenius relation by a series expansion in the exponential term, is also presented. On the basis of their close connection, the same set of parameters is suitable to describe the electrical conductivity as well (238-468 K, 0.003-193 mS/cm). Nevertheless, more elegant alternatives like the usage of the Stokes-Einstein/Nernst-Einstein relation or the Walden rule are highlighted in this work. During this investigation, we additionally found an approach to predict the dielectric constant ε* of an ionic liquid at 298 K by using V(m) and ΔG(solv)(*,∞) between ε* = 9 and 43.

The Reaction of White Phosphorus with NO+/NO2+[Al(ORF)4]−: The [P4NO]+ Cluster Formed by an Unexpected Nitrosonium Insertion†

Despite decades of intense research into polyphosphorus chemistry, our knowledge of homoleptic polyphosphorus cations is still limited to the results of mass spectrometry and quantum chemical calculations. In general, the diamagnetic cage cations with an odd number of phosphorus atoms are more stable, with P9 , composed of two C2v symmetric P5 cages joined by a common phosphonium atom having special stability. This cage was found in one of the few types of simple inorganic phosphorus cluster cations that are known, that is, [P5R2] + (R = Cl, Br, I, Ph, DippN(Cl)NDipp (Dipp = 2,6-diisopropylphenyl)). Those P5 cages are formed by the formal insertion of carbene-analogous PR2 + fragments into the P P bond of P4 (see Ref. [9, 10] for Reviews on P4 activation). Stable carbenes also interact with P4, leading to compounds including P1 up to P12 moieties, depending on the electronic nature of the carbene. Larger cationic P7 cages were recently prepared, but all preparative approaches to true Pn + ions remained futile. However, we expected that an appropriate one-electron oxidant should be able to oxidize P4 (ionization energy (IE) 9.34 eV) and lead to phosphorus cluster cations Pn . Herein we give an account of the reaction of P4 with the salts [NO] [Al(OC(CF3)3)4] [13] (1; IE NO = 9.26 eV) and [NO2] [Al(OC(CF3)3)4] (2 ; IE NO2 = 9.59 eV. At least 2 was expected to be a strong enough oxidant to yield Pn + cations. The novel salt 2 was synthesized in 94 % yield from NO2[BF4] and Li[Al(OC(CF3)3)4] in SO2 solution with precipitation of insoluble Li[BF4]; it was fully characterized by X-ray diffraction and vibrational and NMR spectroscopy (for details, see the Supporting Information). Unexpectedly, the reactions of 1 and 2 with P4 in CH2Cl2 show an analogous process, regardless of the ratios of phosphorus to oxidant employed (between 3P:1 NOx + and 9P:1 NOx ). They form a red intermediate and yield the same yellow final product ([P4NO] [Al(OC(CF3)3)4] (3 ; Scheme 1). Compound 3 may be viewed as the insertion

Establishing consistent van der Waals volumes of polyatomic ions from crystal structures.

Based on temperature (T) dependent crystal structure data of seven organic salts, a radii-based scheme for the calculation of the van der Waals volume (V(vdw)) is analyzed. The obtained volumes (V(vdw,r), r=radius-based) are nearly T independent. An ion volume partitioning scheme is proposed by fixing the anion volumes of [Cl](-), [Br](-), [I](-), [BF(4)](-), [PF(6)](-), [OTf](-) and [NTf(2)](-). The van der Waals volumes (V(vdw,r) (+/-)) of 48 ions are established, with low standard deviations (0.2-3.6 Å(3), 0.1-4.5 % of V(vdw,r) (+/-)). The ion volumes are independent of the counterion and one crystal structure already suffices for their derivation. Correlations of the viscosity with V(vdw,r) via a Litovitz ansatz and our recently derived Arrhenius-type approach prove that these volumes are suitable for the volume-based description and prediction of IL properties. The corresponding correlation coefficient for the latter is R(2)=0.86 for 40 ILs (354 data points) in the T range of 253-373 K.

Modeling the influence of salts on the critical micelle concentration of ionic surfactants

We show for the first time that a phenomenological, augmented volume-based thermodynamics (aVBT) model is capable to predict the critical micelle concentrations of ionic surfactants, including ionic liquids, with added salts. The model also adjusts for the type of salt added by including its molecular volume, which might form a connection to the Hofmeister effect. The other physico-chemically relevant quantities included in the model include surface area and solvation enthalpies.

Li[B(OCH2CF3)4]: Synthesis, Characterization and Electrochemical Application as a Conducting Salt for LiSB Batteries

A new Li salt with views to success in electrolytes is synthesized in excellent yields from lithium borohydride with excess 2,2,2-trifluorethanol (HOTfe) in toluene and at least two equivalents of 1,2-dimethoxyethane (DME). The salt Li[B(OTfe)4 ] is obtained in multigram scale without impurities, as long as DME is present during the reaction. It is characterized by heteronuclear magnetic resonance and vibrational spectroscopy (IR and Raman), has high thermal stability (Tdecomposition >271 °C, DSC) and shows long-term stability in water. The concentration-dependent electrical conductivity of Li[B(OTfe)4 ] is measured in water, acetone, EC/DMC, EC/DMC/DME, ethyl acetate and THF at RT In DME (0.8 mol L(-1) ) it is 3.9 mS cm(-1) , which is satisfactory for the use in lithium-sulfur batteries (LiSB). Cyclic voltammetry confirms the electrochemical stability of Li[B(OTfe)4 ] in a potential range of 0 to 4.8 V vs. Li/Li(+) . The performance of Li[B(OTfe)4 ] as conducting salt in a 0.2 mol L(-1) solution in 1:1 wt % DME/DOL is investigated in LiSB test cells. After the 40th cycle, 86 % of the capacity remains, with a coulombic efficiency of around 97 % for each cycle. This indicates a considerable performance improvement for LiSB, if compared to the standard Li[NTf2 ]/DOL/DME electrolyte system.