Swelling, intercalation, and exfoliation behavior of layered ruthenate derived from layered potassium ruthenate

The intercalation chemistry of a layered protonic ruthenate, H_0.2RuO_2.1·nH₂O, derived from a layered potassium ruthenate was studied in detail. Three phases with different hydration states were isolated, H_0.2RuO_2.1·nH₂O (n=0, 0.5, 0.9), and its reactivity with tetrabutylammonium ions (TBA⁺) was considered. The layered protonic ruthenate mono-hydrate readily reacted with TBA⁺, affording direct intercalation of bulky tetrabutylammonium ions into the interlayer gallery. Fine-tuning the reaction conditions allowed exfoliation of the layered ruthenate into elementary nanosheets and thereby a simplified one-step exfoliation was achieved. Microscopic observation by atomic force microscopy and transmission electron microscopy clearly showed the formation of unilamellar sheets with very high two-dimensional anisotropy, a thickness of only 1.3±0.1 nm. The nanosheets were characterized by two-dimensional crystallites with the oblique cell of a=0.5610(8) nm, b=0.5121(6) nm and γ=109.4(2)° on the basis of in-plane diffraction analysis.     

Reactions of the dications C7H6, C7H7, and C7H8 with methane: Predominance of doubly charged intermediates

The reactions of methane with the dications C₇H₆²⁺, C₇H₇²⁺, and C₇H₈²⁺ generated by electron ionization of toluene are studied using mass-spectrometry tools. It is shown that the reactivity is dominated by the formation of doubly charged intermediates, which can either eliminate molecular hydrogen to yield doubly charged products or undergo charge-separation reactions leading to the formation of a methyl cation and the corresponding C₇H_n+1⁺ monocation. Typical processes observed for dications, like electron transfer or proton transfer, are largely suppressed. The theoretically derived mechanism of the reaction between C₇H₆²⁺ and CH₄ indicates that the formation of the doubly charged intermediate is kinetically preferred at low internal energies of the reactants. In agreement, the experimental results show a pronounced hydrogen scrambling and dominant formation of the doubly charged products at low collision energies, whereas direct hydride transfer prevails at larger collision energies.     

Properties of new inorganic membranes prepared by metal alkoxide methods. Part III: New inorganic lithium permselective ion exchange membrane

Inorganic lithium permselective ion exchange membranes were prepared on a microporous alumina substrate by dip-coating solution containing Si(OC₂H₅)₄, LiOC₂H₅, Mn(OC₂H₅)₂ and C₂H₅OH. The membranes showed ion-selectivity for cation over anion and permselectivity for Li⁺ over Na⁺. The static transport number for cation [K⁺] is 0.75 and the permselectivity for Na⁺ over Li⁺ is 0.29, comparing 2.57 for ordinary organic ion exchange membrane.     

A predictive model for unimolecular reactions: Reactions of unsaturated carbonium ions

The major slow unimolecular reactions undergone by C₄H₇⁺, C₅H₉⁺ and C₆H⁺₁₁ are discussed in terms of a potential surface approach and the organic chemist's concept of mechanism. It is shown that the observed decompositions which do not involve σ-bond formation in the dissociation step are precisely those expected from the model. Further use of the model correctly predicts the slow reactions of C₇H⁺₁₃ which have not previously been reported. The approach also permits useful limits to be set on the transition state energies for reactions involving σ-bond formation in the dissociation step (H₂,CH₄ loss). It is concluded that stepwise addition of ethylene to the allyl cation is preferred to a concerted 4-electron process which is symmetry forbidden.     

Thermal Activation of CH4 and H2 as Mediated by the Ruthenium Oxide Cluster Ions [RuOx]+ (x=1–3): On the Influence of Oxidation States

Thermal gas-phase reactions of the ruthenium-oxide clusters [RuO_x]⁺ (x=1–3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]⁺/CH₄ couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO₂]⁺ brings about the generations of [Ru,O,C,H₂]⁺/H₂O, [Ru,O,C]⁺/H₂/H₂O, and [Ru,O,H₂]⁺/CH₂O, whereas [RuO₃]⁺ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H₂). Regarding the reactions with H₂, as compared to CH₄, both [RuO]⁺ and [RuO₂]⁺ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO₃]⁺ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H−H bond activation. Furthermore, the reactivity patterns of [RuO_x]⁺ (x=1–3) with CH₄ and H₂ have been compared with the previously reported results of Group 8 analogues [OsO_x]⁺/CH₄/H₂ (x=1–3) and the [FeO]⁺/H₂ system. The electronic origins for their distinctly different reaction behaviors have been addressed.     

Chemistry of HCNH+: mechanisms, structures, and relevance to Titan’s atmosphere

The chemistry of HCNH⁺ in Titan’s atmosphere is not completely understood despite previous experimental and theoretical studies. In response to recent suggestions in the literature, we have searched for specific products of the reactions of HCNH⁺ with H₂, CH₄, C₂H₂, and C₂H₄ using the flowing afterglow-selected ion flow tube technique. We have probed for an association mechanism for reaction with H₂, and associative-H₂ loss for the reactions involving CH₄, C₂H₂, and C₂H₄. In all cases, these reaction mechanisms were found to be inefficient pathways for the depletion of HCNH⁺. Our ab initio computational studies characterize the structures and energies for these mechanisms and indicate that the proposed pathways are endothermic or possess reaction barriers. We compare our studies to previous experimental and computational work, and we suggest other ion-neutral reactions with HCNH⁺ that have not been included in previous models of Titan’s ionosphere.     

Ion-Molecule Reactions of Free Phenyl Cations with Diethylamine in the Gas Phase: Radiochemical Study

Ion-molecule reactions of free phenyl cations with diethylamine in the gas phase were studied radiochemically. The reaction practically totally follows the pathway of proton transfer, which occurs in the intermediate complex not only from the incoming cation (C₆H₅ ⁺) but also from the ethyl substituent of the amine. Also, products of the reaction of diethylamine with benzyne (C₆H₄) generated by proton abstraction from the phenyl cation were detected.     

Cover Feature: Are the Accompanying Cations of Doping Anions Influential in Conducting Organic Polymers? The Case of the Popular PEDOT (Chem. Eur. J. 63/2019)

Conducting organic polymers (COPs) are made of a conjugated polymer backbone supporting a certain degree of oxidation. These positive charges are compensated by the doping anions that are introduced into the polymer synthesis along with their accompanying cations. In this work, the influence of these cations on the stoichiometry and physicochemical properties of the resulting COPs have been investigated, something that has previously been overlooked, but, as here proven, is highly relevant. As the doping anion, metallacarborane [Co(C₂B₉H₁₁)₂]⁻ was chosen, which acts as a thistle. This anion binds to the accompanying cation with a distinct strength. If the binding strength is weak, the doping anion is more prone to compensate the positive charge of the polymer, and the opposite is also true. Thus, the ability of the doping anion to compensate the positive charges of the polymer can be tuned, and this determines the stoichiometry of the polymer. As the polymer, PEDOT was studied, whereas Cs⁺, Na⁺, K⁺, Li⁺, and H⁺ as cations. Notably, with the [Co(C₂B₉H₁₁)₂]⁻ anions, these cations are grouped into two sets, Cs⁺ and H⁺ in one and Na⁺, K⁺, and Li⁺ in the second, according to the stoichiometry of the COPs: 2:1 EDOT/[Co(C₂B₉H₁₁)₂]⁻ for Cs⁺ and H⁺, and 3:1 EDOT/[Co(C₂B₉H₁₁)₂]⁻ for Na⁺, K⁺, and Li⁺. The distinct stoichiometries are manifested in the physicochemical properties of the COPs, namely in the electrochemical response, electronic conductivity, ionic conductivity, and capacitance.     

Tricaesium tris(oxalato‐κ2O1,O2)chromate(III) dihydrate

The title compound, Cs₃[Cr(C₂O₄)₃]·2H₂O, has been synthesized for the first time and the spatial arrangement of the cations and anions is compared with those of the other members of the alkali metal series. The structure is built up of alternating layers of either the d or l enantiomers of [Cr(oxalate)₃]³⁻. Of note is that the distribution of the [Cr(oxalate)₃]³⁻ enantiomers in the Li⁺, K⁺ and Rb⁺ tris(oxalato)chromates differs from those of the Na⁺ and Cs⁺ tris(oxalato)chromates, and also differs within the corresponding BEDT‐TTF [bis(ethylenedithio)tetrathiafulvalene] conducting salts. The use of tris(oxalato)chromate anions in the crystal engineering of BEDT‐TTF salts is discussed, wherein the salts can be paramagnetic superconductors, semiconductors or metallic proton conductors, depending on whether the counter‐cation is NH₄⁺, H₃O⁺, Li⁺, Na⁺, K⁺, Rb⁺ or Cs⁺. These materials can also be superconducting or semiconducting, depending on the spatial distribution of the d and l enantiomers of [Cr(oxalate)₃]³⁻.     

Potassium hydrogen diphthalate dihydrate: a new structure and correction to the literature

The title compound, K⁺·[(C₈H₅O₄)₂H]⁻·2H₂O or K⁺·C₁₆H₁₁O₈⁻·2H₂O, was prepared by slow evaporation of an aqueous solution of potassium hydrogen phthalate. The molecular complex consists of a potassium cation coordinated to a proton‐bound hydrogen phthalate dimer and two water mol­ecules. The potassium cation resides on a twofold axis in a distorted square‐antiprism coordination geometry. The compound is isomorphous with the ammonium analogue, previously misidentified. As potassium hydrogen phthalate is frequently used in the manufacture of buffers, organic carbon standards, acidimetric standards and various other products, the crystallization of a compound with a different stoichiom­etery from a solution containing the acidimetric standard has important practical implications.     

Isocyanide addition to MN2(CO)5(Ph2PCH2PPh2)2 and the formation of a four-electron doubly-bridging isocyanide

The reactions of Fe(CO)₅, Fe(CO)₄P(C₆H₅)₃, M(CO)₆ (M  W, Mo, Cr), and (CH₃C₅H₄Mn(CO)₃ with KH and several boron and aluminium hydrides were investigated. Iron pentacarbonyl was converted quantitatively to K⁺Fe(CO)₄-(CHO) by hydride transfer from KBH(OCH₃)₃ allowing isolation of [P(C₆H₅)₃]₂-Nⁿ⁺Fe(CO)₄(CHO)^? in 50% yield. Lower yields were obtained with LiBH(C₂H₅)₃, and other hydride sources gave little or no formyl product. The stability of Fe(CO)₄(CHO)^? in THP was found to depend on the cation, decreasing in the order [P(C₆H₅)₃]₂N⁺ > K⁺ > Na⁺ > Li⁺. No formyl complexes were isolated and no spectroscopic evidence for formyl formation was observed in the reactions of the other transition metal carbonyls with several hydride sources. Fe(CO)₄-P(C₆H₅)₃ gave K₂Fe(CO)₄ when treated with KHB(OCH₃)₃. When treated with LiBH(C₂H₅)₃, W(CO)₆ gave a mixture of HW₂(CO)₁₀^?and (OC)₅W(COC₂H₅)^?; the latter was methylated to give the carbene complex (OC)₅WC(OCH₃)C₂H₅.     

Mössbauer effect studies on alkali tris(maleato) ferrates(III)

Mössbauer spectra of alkali tris(maleato) ferrates(III), i.e., M₃[Fe(C₂H₂C₂O₄)₃]·nH₂O [M=Li, Na, K, Cs] at 300 K display a doublet. The Mössbauer parameters indicate these complexes to be high spin with octahedral symmetry. The isomer shift shows a decreasing trend with the increase in electronegativity/polarizing power of the substituent cation (Li⁺, Na⁺, K⁺, Cs⁺). A linear correlation between isomer shift values and the (Fe?O) stretching frequencies has also been observed.     

Relationship between the Physicochemical Properties of Electrolytes and the Electronic Structure of Solvated Alkali Metal Cations

Group theoretical analysis and linear combinations of molecular orbitals of the cation and solvent are used to establish the nature and stability of bonds and hence the electric mobility of the cation and the viscosity of the electrolyte depending on the type of cation (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) and molecules (H₂O, NH₃, H₂CO, (CH₃)₂CO, CH₃CN). Solvation effects on the UV photoelectron and intramolecular vibrational IR and NMR spectra are revealed.     

Photofragmentation of 2‐Deoxy‐D‐Ribose Molecules in the Gas Phase

We have measured the synchrotron‐induced photofragmentation of isolated 2‐deoxy‐D ‐ribose molecules (C₅H₁₀O₄) at four photon energies, namely, 23.0, 15.7, 14.6, and 13.8 eV. At all photon energies above the molecule′s ionization threshold we observe the formation of a large variety of molecular cation fragments, including CH₃⁺, OH⁺, H₃O⁺, C₂H₃⁺, C₂H₄⁺, CH_xO⁺ (x=1,2,3), C₂H_xO⁺ (x=1–5), C₃H_xO⁺ (x=3–5), C₂H₄O₂⁺, C₃H_xO₂⁺ (x=1,2,4–6), C₄H₅O₂⁺, C₄H_xO₃⁺ (x=6,7), C₅H₇O₃⁺, and C₅H₈O₃⁺. The formation of these fragments shows a strong propensity of the DNA sugar to dissociate upon absorption of vacuum ultraviolet photons. The yields of particular fragments at various excitation photon energies in the range between 10 and 28 eV are also measured and their appearance thresholds determined. At all photon energies, the most intense relative yield is recorded for the m/q=57 fragment (C₃H₅O⁺), whereas a general intensity decrease is observed for all other fragments— relative to the m/q=57 fragment—with decreasing excitation energy. Thus, bond cleavage depends on the photon energy deposited in the molecule. All fragments up to m/q=75 are observed at all photon energies above their respective threshold values. Most notably, several fragmentation products, for example, CH₃⁺, H₃O⁺, C₂H₄⁺, CH₃O⁺, and C₂H₅O⁺, involve significant bond rearrangements and nuclear motion during the dissociation time. Multibond fragmentation of the sugar moiety in the sugar–phosphate backbone of DNA results in complex strand lesions and, most likely, in subsequent reactions of the neutral or charged fragments with the surrounding DNA molecules.     

Unique protonation behavior of cationic free-base porphyrins in the interlayer space of transparent solid films comprising layered α-zirconium phosphate

The protonation behavior of α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin (H₂TMPyP) in the interlayer space of transparent solid films comprising layered α-zirconium phosphate was investigated. It was found that the exposure of H₂TMPyP-impregnated films to aqueous HCl resulted in pyrrole group protonation and induced a color change from yellow to greenish yellow. The two pK_a values of H₂TMPyP, determined as 2.4 and 2.6, exceeded those determined in aqueous solution (0.80 and 2.06), which was attributed to the condensation of H⁺ in the interlayer space caused by the cation exchange reaction between H⁺ in the aqueous solution and n-butylamine intercalated in the interlayer space.     

SiH+5 and the proton affinity of monosilane

Tandem mass spectrometric studies show that SiH⁺₅ is formed in bimolecular reactions of SiH₄ and NH⁺₂, C₂H⁺₃, C₂H⁺₆ and C₃H⁺₈ ions. The dependence of the reaction cross sections on ion energy indicates the formation of SiH⁺₅ from NH⁺₂, C₂H⁺₃, and C₂H⁺₆ to be exothermic reactions, while formation from C₃H⁺₈ is endothermic. Using known thermochemical data, these facts permit the assignment of 150 and 156 kcal/mole to the lower and upper limits of the proton affinity of monosilane.     

Conformational Transformations of (C12H25NH3+)(Pyridinesulfonate) in the Solid State

The phase‐transition behaviors, crystal structures, and dielectric properties of four kinds of simple 1:1 organic salts of (C₁₂H₂₅NH₃⁺)(benzenesulfonate) and (C₁₂H₂₅NH₃⁺)(pyridine sulfonates) were examined from the viewpoint of intermolecular hydrogen‐bonding interactions and dynamic conformational transformation in molecular assemblies. Crystals of (C₁₂H₂₅NH₃⁺)(benzenesulfonate) and (C₁₂H₂₅NH₃⁺)(3‐pyridinesulfonate) were isostructural and solid–solid and solid–liquid‐crystal smectic A (SmA) phase transitions were observed. These two crystals formed rodlike cation–anion assemblies. However, the two salts, (C₁₂H₂₅NH₃⁺)(2‐pyridinesulfonate) and (C₁₂H₂₅NH₃⁺)(4‐pyridinesulfonate), formed largely bent L ‐shaped cation–anion conformations. Interesting conformational transformations from rodlike to L ‐shaped assemblies were observed in (C₁₂H₂₅NH₃⁺)(2‐pyridinesulfonate) and (C₁₂H₂₅NH₃⁺)(3‐pyridinesulfonate).     

Photoelectron—photoion-coincidence measurements on 2,4-hexadiyne

2,4-Hexadiyne cations in their first excited electronic state òE_ureveal a decay by an effective competition between fluorescence and fragmentation. The present photoelectron—photoion-coincidence study of 2,4-hexadiyne cation provides individual breakdown diagrams for the parent ion and the seven dominant fragment ions, C₆H₅⁺, C₆H₄⁺, C₅H₃⁺, C₄H₄⁺, C₄ H₃⁺, C₄H₂⁺, C₃H₃⁺ in the ionisation energy regions populated by He(Iα) excitation. Additional information concerning the rate constants and the kinetic energy released on the formation of C₆H₅⁺ and C₄H₃⁺ are deduced from the time-of-flight (TOF) distributions of these ions. The appearance potentials for the two fragments C₄H₃⁺ and C₄H₂⁺ could also be measured, as these lie well within the third band of the He(Iα)-PE spectrum.     

über den Mechanismus der Extraktion von Gold(III) mit gesÄttigten aliphatischen Monoketonen

It has been found, that gold(III) is extracted by way of a hydrate-solvated mechanism from a hydrochloric acid medium with aliphatic ketones (in the presence or absence of a solvent). When the methylethylketone is used as an extractant, the solvate has the following composition:M ⁺(H₂O)_3–14 (MEK)₇AuCl₄ ^?, whereM ⁺=H⁺, Li⁺, K⁺, Na⁺, NH₄ ⁺. If the cation is a heavy non-solvated ion, for instance N(C₂H₅)₄ ⁺, the solvate is free of water. The active extractant solvates also the anion AuCl₄ ^?, a fact which could explain the high values of the coefficient of distribution.     

The decay of 1-chloropropyne cation studied by photoelectron-photoion coincidence spectroscopy

The decay of internal energy selected 1-chloropropyne cations is investigated using the fixed wavelength (He-Iα) photoelectron-photoion coincidence technique. The breakdown curves of the molecular ion and the C₃H₂Cl⁺, C₃HCl⁺, CCl⁺, C₃H⁺₃, C₃H⁺₃, C₃H⁺ fragment ions are reported. For 1-chloropropyne cations initially formed in their $\text{A}\text{?}$²E state it is found that four fragmentation channels compete with a non-dissociative relaxation pathway. The average kinetic energies released on formation of C₃H⁺₃ and C₃H⁺₃ are deduced from the time-of-flight distributions of these fragment ions measured at different internal energies of the molecular ion. The coincidence data are supplemented by electron impact appearance energies. The obtained decay pattern of 1-chloropropyne cation is compared with the breakdown diagrams reported for the C₃H⁺₄ isomers, i.e. allene-, propyne- and cyclopropene cations.