DME Solution Research Articles

Synthesis, Structure, and Bonding of d0/fn Metallacarboranes Incorporating the η7-Carboranyl Ligand

Treatment of 1,2-(C6H5CH2)2-1,2-C2B10H10 with excess Na or Li metal in THF followed by reaction with MCl3 in the presence of excess alkali metal gave novel 13-vertex closo-metallacarboranes {[(C6H5CH2)2C2B10H10]M(THF)}2{Na(THF)3}2·2THF (M = Dy (1), Y (2), Er (3)) or [{(C6H5CH2)2C2B10H10}M(THF)]2[Li(THF)4]2(M = Y (5), Er (6)) in moderate to good yield, respectively. Recrystallization of 3 from a DME solution afforded DME-coordinated metallacarborane {[(C6H5CH2)2C2B10H10]Er(DME)}2{Na(DME)2}2 (4). 2 and 5 are the first examples of d0 metallacarboranes incorporating a η7-carboranyl ligand. All of these complexes have been fully characterized by various spectroscopic date, elemental analyses, and X-ray diffraction studies. Molecular orbital calculations indicate that the metal−carborane bonding is well delocalized and can be described as the orbital interactions between the metal's five d orbitals and the cage's five symmetry-adapted frontier orbitals. It is anticipated that only the d0/fn transition metal ion...

Variety of naphthalene coordination modes in the polynuclear (pentamethylcyclopentadienyl) lutetium naphthalene complex [(C5Me5Lu)3(C10H8)(C10H7)(H)][(Na(THF)3]2C10H8

The reaction of C5Me5LuCl2 with sodium naphthalenide in DME solution affords the mononuclear complex C5Me5LuC10H8(DME) (1) in 48% yield besides naphthalene and NaCl. The same reaction in THF solution gives a series of products: (C5Me5)Lu(C10H8)2Na(THF)x (2), [(C5Me5Lu)3(C10H8)(C10H7)(H)][Na(THF)3]2C10H8 (3) and [(C5Me5)LuH(THF)]3(C10H7) (4). The polynuclear complex 3 with several modes of Luȁnaphthalene interaction has been isolated in low yield in a monocrystalline form. An X-ray diffraction study has shown that complex 3 consists of three C5Me5Lu units joined by two non-planar bridging C10H8 and C10H7 ligands via different kinds of naphthalene coordination mode. The third planar C10H8 group is not involved in coordination sphere of the Lu atoms, and is on an inversion centre in the crystal structure. The Na atom in 3 is bonded to three THF molecules and η3-bonded to the bridging C10H7 group.

High Resolution ESR Spectra as Obtained by FT-ESR Spectroscopy

Abstract Superhyperfine couplings due to K+ in K+/ duroquinone− ion-pair system in DME solution were clearly observed by use of FT-ESR spectroscopy. The superhyperfine coupling constant obtained at room temperature suggested that the population of the unpaired electron on the 39K+ 4s orbital was as small as 0.14%.

Wechselwirkungen in Kristallen, 63 [1, 2] Kristallisation und Strukturbestimmung von 1,2-Dimesitoylbenzol und von Bis(hydrogen-1,2-dimesitoylbenzol)-dinatrium-bis(ethylendiamin)/Interactions in Crystals, 63 [1, 2] Crystallization and Structure Determination of 1,2-Dimesitoylbenzene and of Bis(hydrogen-1,2-dimesitoylbenzene)-disodium-bis(ethylendiamine)

Chelate complexes of 1,2-dimesitoylbenzene radical anion with alkali metal cations exhibit in aprotic solution extremely large ESR /ENDOR metal coupling constants. For rationalization, structures of both the neutral molecule (H3C)3H2C6 - CO - C6H4 - CO - C6H2(CH3)3, in which the two carbonyl groups are twisted out of the benzene ring plane by dihedral angles of ± 3̄7̄°, and a sodium contact ion quadruple have been determined. One of the dimers [dimesitoylbenzeneH⊖ (Na⊕H2N H2C - CH2NH2)]2, although generated by Na metal mirror reduction of 1,2-dimesitoylbenzene in aprotic DME solution with added ethylendiamine for better electron transfer, surprisingly contains two 245 pm short (!) hydrogen bridges ⊖O ··· (H)O and in addition two solvation bridges e ⊖O ··· Na⊕(H2NH2C - CH2NH2) ··· O⊖. Results of MNDO calculations based on the experimental coordinates support the proposed concept.

Synthese und Kristallstrukturen von Diazadien-Komplexen der Erdalkalimetalle / Syntheses and Crystal Structures of Diazadiene Complexes of the Alkaline Earth Metals

(DME)2] 1 (R = C6H4-4-CH3; DME = dimethoxyethane) was prepared by reaction of calcium with NR=CPh-CPh=NR in DME solution. The compound forms orange, moisture sensitive crystals, which were characterized by an X-ray structure determination [space group orthorhombic, P212121, Z = 4, 4634 observed unique reflections, R = 0.046; lattice dimensions at –70 °C: a = 1340.2(3), b = 1528.1(3), c = 1609.1(3) pm]. The calcium atom is coordinated by the four oxygen atoms of two chelating DME molecules and two nitrogen atoms of the diazadiene ligand, bonded in its enediamide form. [Ba2(DME)3(NPh–CPh=CPh–NPh)2 · DME] 3 was obtained from barium metal and NPh=CPh-CPh=NPh in DME solution as red crystals [space group monoclinic, P2l/c, Z = 4, 4000 observed unique reflections, R = 0.166; lattice dimensions at -70 °C: a = 1704.5(3), b = 1786.1(4), c = 2177.4(4) pm, β = 105.98(3)°]. The two barium atoms are bridged by two differently bonded diazadiene ligands (μ2-Ν,Ν′;μ-Ν, σ-Ν′). Additionally, one of the barium atoms is coordinated to two DME molecules and the other one to only one of the ether molecules. A further DME molecule is a constituent of the crystal lattice.

Elektronentransfer und Ionenpaar-Bildung, 34 [1 - 3] Einkristallstruktur des Solvens-separierten Radikalionenpaares [9,9′-Bianthryle·⊖][Na⊕(DME)3] / Electron Transfer and Ion Pair Formation, 34 [1-3] Single Crystal Structure of the Solvent-Separated Ion Pair [9,9′-Bianthryle·⊖][Na⊕(DME)3

Abstract The one-electron transfer to large π-delocalized hydrocarbons provides an interesting possibility to crystallize solvent-separated ion-pair salts containing optimally solvated cations. Accordingly, the reduction of 9.9′-bianthryl in aprotic 1.2-dimethoxyethane (DME) solution at a sodium metal mirror allows to grow dark blue, brick-like crystals of its radical anion and threefold DME-solvated sodium cation. The structure of the radical anion is very similar to that recently published for the neutral molecule. According to AM 1 enthalpy hypersurface calculations based on the structural data, the torsion angle between 60° and 120° is determined by the lattice packing and the negative charge is -π-delocalized predominantly within only one anthracene subunit. The counter cation [Na⊕(DME)3], reported only three times so far, shows a sixfold propeller-like coordination of approximate D3 skeletal symmetry with contact distances Na⊕···O between 232 and 243 pm and angles ≮ONa⊕O varying between 69° and 159°. Due to the small repulsion between the chelating DME molecules, the isodesmically calculated Na⊕ solvation enthalpy is more negative than that of the analogous tetrahydrofuran complex [Na⊕(THF)6] - as confirmed by the laboratory experience that salts of less stable anions are preferentially crystallized from a strongly cation solvating DME solution.

Study of Lithium Salts in Solvents with Low Dielectric Constant by Means of Ultrasonic Velocity and Absorption

Abstract Ultrasonic velocity at 1.92 MHz has been measured precisely in 1,2-dimethoxyethane (DME), acetonitrile (AN), and propylene carbonate (PC) solutions of lithium tetrafluoroborate (LiBF4) and in DME solution of lithium hexafluoroarsenate (LiAsF6) at 25 °C. The molar relative sound velocity for the LiBF4 solution has been found to show a clear inflection in the DME solution at 0.01 mol dm−3 and in the AN one at 0.02 mol dm−3 concentration though such an inflection has not been found in PC solution. The inflection for DME solution of LiAsF6 is found near 0.0013 mol dm−3. These sound velocity inflection points are believed to be due to formation of triple ions or dimers (quadrupoles) in solvents of low dielectric constants. Ultrasonic absorption coefficients in DME solutions of LiAsF6 and LiBF4 have been measured in the frequency range from 8.5 to 220 MHz by a pulse method as a function of their concentration. A single relaxational absorption has been observed in both solutions. In DME solution of LiBF4, the observed relaxational absorption mechanism has been attributed to the dimerization reaction, as reported by Maaser et al. (J. Phys. Chem., 88, 5100 (1984)). Our determination of the rate and thermodynamic constants, however, has taken into account the presence of triple ions. The results in LiAsF6 solutions are compared to those reported by Farber et al. (J. Phys. Chem., 87, 3515 (1983)) in the concentration range higher than 0.1 mol dm−3. At concentrations lower than that, however, a phenomenon with a concentration dependent relaxation frequency has been found. From a consideration of various reaction models, it has been concluded that the relaxation is associated with formation of triple ions in solution. The rate and thermodynamic parameters have been determined from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength.

Amino acid stimulation of Na, K‐ATPase activity in rat proximal tubule after high‐protein diet

Ouabain-sensitive (OS) O2 consumption was determined in proximal tubular cells from weanling rats fed 21% (normal-protein, NP) or 50% (high-protein, HP) protein diet for 4 days. Butyric acid 10(-3)M was added as a substrate for mitochondrial respiration and the ionophore amphotericin B (10 micrograms ml-1) was used to sodium-load the cells. OS respiration was higher in HP than in NP cells in both DME and amino acid-free electrolyte solution (ES). Amphotericin B significantly increased OS respiration in both NP and HP cells, implying that the Na-K pump was activated by increased intracellular Na. In cells incubated in ES, addition of amino acids stimulated OS respiration significantly in HP cells (16.9 +/- 1.4 vs 21.2 +/- 1.1 nmol min-1 mg-1 protein) and in NP cells (13.9 +/- 0.3 vs 14.9 +/- 0.6 nmol min-1 mg-1 protein). Stimulation was significantly higher in HP cells (26 +/- 4%) than in NP cells (7 +/- 4%) (P less than 0.001). The amino acids did not stimulate ouabain-insensitive respiration. The results indicate that an HP diet to weanling rats will increase proximal tubule cell Na, K-ATPase-dependent respiration by enhancing Na entry via the Na-amino acid symports.

Chemically desodiated thiochromites as cathode materials in secondary lithium cells

The chemical desodiation of non-doped and vanadium-doped sodium thiochromites has been studied. The changes in the chemical composition and X-ray diffraction patterns during desodiation of the stoichiometric compound reveal that the vanadium-doped thiochromite can be more effectively desodiated. The presence of vanadium in the disulfide layers enhances the covalency of the MS bond; this probably facilitates a first order phase transition of the vanadium-doped material during deintercalation of both Na + and Li +. The electrochemical performance of cathodes prepared from the chemically desodiated, vanadium-doped thiochromite is assessed by cycling in a 1 M LiClO 4/PC + DME solution at a 3 h rate between 1.8 and 3.4 V. The volumetric energy density of the pressed cathodes is 0.51 W h cm −3 at the 100th cycle and drops to 0.35 W h cm −3 after 500 cycles.

ChemInform Abstract: Alkali Metal Hydrogen Tetraphosphides, M(I)HP4 ‐ the First Salts of Bicyclo(1.1.0)tetraphosphanes ‐

Abstractare obtainable by reduction of P4 with naphthalene lithium or naphthalene sodium/potassium in DME solution.

Syntheses of transition metal-graphite-organic molecule ternary compounds

Ternary graphite intercalation compounds of transition metal and organic molecule were synthesized by the reaction between KC8 and transition metal chloride in an organic solvent. The first-stage graphite intercalation compounds of either Co or Fe and tetrahydro- furan (THF) had the identity period lc of 8.9 A. The second-stage compound with lc = 12.6 A was also obtained. The compound of Co-graphite-dimethoxyethane (DME) with lc = 12.2 A was synthesized in DME solution. All of these compounds were attracted by a magnet through the glass wall of flask. The magnetic residue compound which was stable in air was prepared from the ternary intercalation compounds by washing repeatedly with water and then heating to 100 °C under evacuation. From the experimental results — large content of Co up to 33 wt % and no aggregation of Co under XMA, magnetic properties (saturation magnetization of about 6.6 emu/g and attracted by making their basal plane parallel to the magnetic field) and exfoliated above 200 °C — it was concluted to be a ternary residue compound which contains an effective amount of cobalt and THF between the graphite layer planes.

Polymerization by alkaline earth metal compounds—II Polymerization of 2- and 4-vinylpyridine, styrene and butadiene by triphenylmethyl derivatives of calcium, strontium and barium

Investigations are reported on polymerizations of 2- and 4- vinylpyridine, styrene and butadiene by a series of related alkaline earth metal initiators, Ph 3CMX(THF) n (M = Ca, Ba, X = Cl, n = 2; M = Ca, X = Br, n = 4; M = Sr, X = Cl, n = 4; M = Sr, X = Br, n = 5) in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) at various temperatures and in the absence of solvent. The polymers have been examined by GPC and aspects of their microstructures determined by 13C and/or 1H NMR spectroscopy and, for polybutadiene, i.r. spectroscopy. Poly-2-vinylpyridine produced by Ph 3CMX(THF) n is rich in isotactic content; the isotacticity is higher for polymer formed in THF than DME solution, falls with change of initiator in the order M = Ca > Sr > Ba and, in DME, is greater when X = Br. The tacticities of poly-4-vinylpyridine and polystyrene are similar to those obtained from related organometallic initiators. The 1,4-content of polybutadiene decreases with initiator Ph 3CMX(THF) n in the order M = Ba > Sr > Ca; the trans-1,4 structure generally predominates except when M = Ba from which cis-1,4 links are formed in comparable amounts.

Reactions of pyrazine radical anions in solution. II. Oxidation reduction equilibrium between radical anions of pyrazine and anthracene

The relative electron affinity of pyrazine (pz) and anthracene (A) has been determined in 1,2-dimethoxyethane (dme) solution. Electron spin resonance and spectrophotometric methods were employed to study the equilibrium: (pz-,K+) + A ←→ pz + (A-,K+) The equilibrium constant for this reaction has been calculated, after consideration of other reactions of the pyrazine radical anions in the solution, and modified for the case of the equilibrium reaction of the unassociated radical anions. The resultant value has been used to calculate the relative solution electron affinity of pyrazine, which was determined to be of the order of 0.09 eV smaller than that of anthracene in dme. The free energies of solvation of the radical anions of pyrazine and anthracene have been estimated and a value of the gaseous electron affinity of pyrazine calculated.

An ESR and ENDOR study of the hexahelicene anion radical

Ten hyperfine coupling constants obtained from the ENDOR spectrum of the hexahelicene anion radical are reported. Since only eight are expected by symmetry, it is inferred that the radical exists as an ion pair in DME solution. The coupling constants are compared to those calculated from HMO theory.

ESR Study of the Ion Pairs of the Phthalonitrile Anion with Alkali Metals

Abstract From the ESR spectroscopic point of view, there are two distinct species of ion pairs of the phthalonitrile anion with the lithium ion in ethereal solvents. One corresponds to the locating of the cation in close proximity to a cyano group. Its ESR spectrum exhibits the loss of twofold symmetry in the spin distribution on the anion (spectrum I) or an alternating line width (spectrum II), depending on the transfer rate of the cation between the two cyano groups. The other species refers to the locating of the cation probably in the spacing between the two cyano groups. The appearance of its spectrum (spectrum III) is similar to that of the free anion. The DME or THF solution gives spectrum II; the ethyl ether solution, spectrum III, and the THP or MeTHF solution, the superposition of spectrum I or II upon III. A similar two species are found in the sodium ion pair. The negative spin density at the meta-carbon atom to the cyano group where the cation is located has been found. The solvent and the temperature effects on the alkali metal splittings, a semi-quantitative treatment of the alternating line width, and the variations in the proton and nitrogen coupling constants are also described.

Electron Spin Resonance of Semiquinones: Spin-Density Distribution and Carbonyl Sigma—Pi Parameters

The spin-density distributions in the 1,4-benzosemiquinone and 2,5-dioxy-1,4-benzosemiquinone ions have been estimated by measuring the proton and 13C splittings and using reasonable choices for the values of the sigma—pi parameters which relate the splittings to the spin densities for C–C and C–H bonds. The determination of the signs as well as the magnitudes of the 13C splittings was required to obtain the spin densities. With QCHH=−27.0 G in the relation aiH=QCHHρi π between proton splitting aiH and carbon-atom—pi-electron spin density ρiπ, the sigma—pi parameters for the 13C splitting at a carbonyl position were found to be QCOC=17.7 G and QOCC=−27.1 G. The values of QCOC and QOCC depend on the value assumed for QCHH. Contrary to earlier predictions made on the basis of molecular orbital calculations, the sign of the 13C splitting from the 2 position of the p-benzosemiquinone ion was found to be negative. This discrepancy results because the MO calculations were performed so as to reproduce proton splittings rather than the entire spin-density distribution, a procedure that is insensitive to the spin densities on the carbonyl carbon and oxygen atoms. New MO calculations were performed to fit the spin densities at all the positions in the radical. The results show that calculations fitted to proton splittings alone are inadequate for predicting spin densities at ``blind'' positions such as those at the carbon and oxygen atoms of a carbonyl group, or the nitrogen and oxygen atoms of a nitro group. Carbon-13 splittings were also observed in the anthrasemiquinone ion in both ethanol and 1,2-dimethoxyethane (DME) solutions. The sign of the 9-position 13C splitting changes from +0.70 G in ethanol to −0.47 G in DME solution. By using the sigma—pi parameters for the carbonyl group carbon atom, the spin densities were determined for this radical and MO calculations performed to reproduce the spin-density distributions. The variation of the splittings in the p-benzosemiquinone ion with solvent composition could be accounted for quantitatively by using the newly determined sigma—pi parameters.