K2MCl5(M = La—Dy) und Rb2MCl5 (M = La—Eu): Ino-Chloride mit siebenfach koordinierten Seltenen Erden

K₂MCl₅(M = La—Dy) and Rb₂MCl₅ (M = La—Eu): Ino-chlorides with Seven—Coordinated Rare Earths K₂PrCl₅ crystallizes with a = 1263.1(8), b = 875.6(3), c = 797.3(4) pm, Z = 4, orthorhombic, Pnma, isotypic to e. g. Y₂HfS₅. Monocapped trigonal prisms (C.N. = 7) are connected to chains via common edges in [010] direction according to [PrCl_3/1^tCl_4/2^k]^2? with d?(Pr? Cl) = 281 pm. The chlorides K₂MCl₅ (M = La—Dy) and Rb₂MCl₅ (M = La—Eu) are isotypic to K₂PrCl₅. Thermal expansion of Rb₂PrCl₅ in [010] direction is remarkably smaller than parallel to (010).     

Mass spectrometric studies of the Decomposition and the Heat of Formation of CuInS2(s)

The equilibrium vaporization of CuInS₂(s) was studied by Knudsen cell mass spectrometric techniques in the temperature range 902—1110 K. Based on these and independent congruency studies, CuInS₂(s) decomposes under steady-state conditions according to the reaction 2CuInS₂(s) = Cu₂S(s) + In₂S(g) + S₂(g). During the initial transient period of the vaporization of CuInS₂, the ion intensities of In₂S⁺ and S₂⁺ change and assume steady-state values after some time. A second-law evaluation of intensity versus temperature data, obtained under steady-state conditions, yielded a value for the heat of the above decomposition reaction (2 moles of CuInS₂) of δH 630.9 ± 26 kJ. With this quantity and auxiliary thermochemical data, the enthalpy of formation of CuInS₂(s) was computed to be δH = ?221.7 ± 13 kJ/mol.     

Luminescent Pd(II) Complexes with Tridentate − Aryl-pyridine-(benzo)thiazole Ligands

Cyclometalated Pd(II) complexes generally show inferior luminescence properties compared with their Pt(II) analogues. The established approach employing tridentate cyclometalating ligands has allowed us to create a series of square planar Pd(II) complexes [Pd( )X] from their protoligands H (2-(6-phenylpyridin-2-yl)thiazoles and -benzothiazoles; coligands X=Cl, Br, I) with extensive variations at the C_arene group (phenyl, naphthyl, fluorenyl), the central N_pyridine (pyridine, 4-phenylpyridine, 3,5-di-tert-butyl-4-phenylpyridine), and the peripheral N_thiazole (thiazole, benzothiazole) to probe for structural factors that might enhance efficient luminescence. Long-wavelength bands at 400–500 nm were assigned to transitions into mixed ligand-centred/metal-to-ligand charge transfer (MLCT) states based on time-dependent (TD)DFT calculations. The MLCT contributions are rather low, in agreement with relatively long lifetimes and high photoluminescence quantum yields of up to 0.79 recorded in frozen glassy solvent matrices at 77 K along with emission bands showing pronounced vibrational progressions and peaking at about 520 nm. No photoluminescence was observed at 298 K in solution. Variation of the ligand allowed to shift the experimental absorption energies from about 2.4 to 2.7 eV, in good agreement with the electrochemical band gaps (2.58 to 2.81 eV). The theoretical absorption and emission spectra excellently reproduced the experimental trends.     

Bildung von gasförmigem POCl Massenspektrometrische und Matrix-IR-Untersuchungen

Formation of Gaseous POCl Mass-spectrometric and Matrix-IR Investigations The formation of gaseous POCl by reaction of POCl₃ with silver at about 1100 K has been shown by mass spectrometric and IR matrix investigations. The heat of formation and entropie has been calculated at ΔH₂₉₈₂₉₈ (POCl) = ?250.7 kJ/Mol, S₂₉₈ (POCl) = 274.5 J/K · Mol. An approximate force constant calculation is presented as the three possible vibrational frequencies (1257.7 cm^?1, 489.4 cm^?1, 308.0 cm^?1) and some isotopic shifts (¹⁶O/¹⁸O; ³⁵Cl/³⁷Cl) are observed in an Ar-matrix.     

Infrared Spectroscopic Evidence for a Heterogeneous Reaction between Ozone and Sodium Oleate at the Gas–Aerosol Interface: Effect of Relative Humidity

The heterogeneous ozonolysis of sodium oleate aerosols in an aerosol flow tube is reported under different relative humidity (RH%) conditions. Submicron sodium oleate particles were exposed to a known ozone concentration and the consumption of sodium oleate was monitored by infrared spectroscopy. When the experimental results are treated as a surface‐mediated reaction (i.e., following a Langmuir–Hinshelwood type mechanism), the following parameters are obtained: at low RH%, = (3 ± 1) × 10^?16 cm³ molecule^?1 and = (0.046 ± 0.006) s^?1; at high RH%, = (6 ± 2) × 10^?16 cm³ molecule^?1 and = (0.21 ± 0.05) s^?1. From these pseudo–first‐order coefficients, the reactive uptake coefficients for dry and aqueous sodium oleate aerosols are calculated as (1.5 ? 0.5) × 10^?7 and (1.7 ? 0.7) × 10^?6, respectively. Hydrated oleate aerosols display both an increase in the ozone trapping ability and an increase in the effective rate reaction at the droplet surface compared to dry aerosol surfaces. These observations may provide an explanation for some of the variability observed between lab studies of dry ozonolysis and real‐world, atmospheric lifetimes of oleic acid–related species.     

Lanthanide metals in the boron cages: Computational prediction of M@Bn (M = Eu,Gd; n = 38, 40)

Endohedral metalloborofullerenes (EMBFs) are novel boron analogues of the famous endohedral metallofullerenes (EMFs). Many EMBFs have been proposed by theoretical calculations thus far. However, in sharp contrast to EMFs, which trap most of the lanthanides with f electrons inside the cages, the corresponding lanthanide‐based EMBFs have never been reported. In this work, the encapsulation of Eu and Gd in the B₃₈ and B₄₀ fullerenes was studied by means of density functional theory calculations. Our results revealed that Gd@B₃₈(⁹A), Eu@B₄₀(⁸B₂), and Gd@B₄₀(⁷A″) all favor the endohedral configuration, and the electronic structures can be described as Gd³⁺@ , Eu²⁺@ , and Gd³⁺@ with jailed f electron spins. The large binding energies and sizable HOMO–LUMO gaps suggest that they may be achieved experimentally. They feature σ and π double aromaticity, and their excellent stabilities were confirmed by the Born–Oppenheimer molecular dynamics simulations. Finally, the infrared and UV/vis spectra were simulated to assist experimental characterization.     

Confined Lewis Pairs: Investigation of the X−→Si20 Interaction in Halogen-Encapsulating Silafulleranes

A joint theoretical and experimental study on 32 endohedral silafullerane derivatives [X@Si₂₀Y₂₀]⁻ (X=F-I; Y=F-I, H, Me, Et) and -[Cl@Si₂₀H₁₂Y₈]⁻ (Y=F-I) is presented. First, we evaluated the structure-determining template effect of Cl⁻ in a systematic series of concave silapolyquinane model systems. Second, we investigated the X⁻→Si₂₀ interaction energy ( ) as a function of X⁻ and Y and found the largest values for electron-withdrawing exohedral substituents Y. Given that X⁻ ions can be considered as Lewis bases and empty Si₂₀Y₂₀ clusters as Lewis acids, we classify our inseparable host–guest complexes [X@Si₂₀Y₂₀]⁻ as “confined Lewis pairs”. Third, ³⁵Cl NMR spectroscopy proved to be highly diagnostic for an experimental assessment of the Cl⁻→Si₂₀ interaction as the paramagnetic shielding and, in turn, (³⁵Cl) of the endohedral Cl⁻ ion correlate inversely with . Finally, we disclose the synthesis of [PPN][Cl@Si₂₀Y₂₀] (Y=Me, Et, Br) and provide a thorough characterization of these new silafulleranes.     

A Cationic Unsaturated Platinum(II) Complex that Promotes the Tautomerization of Acetylene to Vinylidene

Complex [PtMe₂(PMe₂Ar )] ( 1 ), which contains a tethered terphenyl phosphine (Ar =2,6‐(2,6‐ⁱ Pr₂C₆H₃)₂C₆H₃), reacts with [H(Et₂O)₂]BAr_F (BAr_F⁻=B[3,5‐(CF₃)₂C₆H₃]₄⁻) to give the solvent (S) complex [PtMe(S)(PMe₂Ar )]⁺ ( 2⋅S ). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C₂H₄) to afford the corresponding adducts, treatment of 2⋅S with C₂H₂ yielded instead the allyl complex [Pt(η³‐C₃H₅)(PMe₂Ar )]⁺ ( 6 ) via the alkyne intermediate [PtMe(η²‐C₂H₂)(PMe₂Ar )]⁺ ( 5 ). Deuteration experiments with C₂D₂, and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a Pt^II‐promoted HC≡CH to :C=CH₂ tautomerization in preference over acetylene migratory insertion into the Pt−Me bond.     

Single‐Chain Self‐Folding of Synthetic Polymers Induced by Metal–Ligand Complexation

The controlled folding of a single polymer chain is for the first time realized by metal‐ complexation. α,ω‐Bromine functional linear polymers are prepared via activators regenerated by electron transfer (ARGET) ATRP (_,SEC = 5900 g mol⁻¹, Đ = 1.07 and 12 000 g mol⁻¹, Đ = 1.06) and the end groups of the polymers are subsequently converted to azide functionalities. A copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction is carried out in the presence of a novel triphenylphosphine ligand and the polymers to afford homotelechelic bis‐triphenylphosphine polymeric‐macroligands (MLs) (_,SEC = 6600 g mol⁻¹, Đ = 1.07, and 12 800 g mol⁻¹, Đ = 1.06). Single‐chain metal complexes (SCMCs) are formed in the presence of Pd(II) ions in highly diluted solution at ambient temperature. The results derived via ¹H and ³¹P{¹H} NMR experiments, SEC, and DLS unambiguously evidence the efficient formation of SCMCs via metal ligand complexation.

     

Shock Tube Study of Dimethylamine Oxidation

Dimethylamine (DMA) ignition delay times and OH time histories during the oxidation process were investigated behind reflected shock waves. The ignition delay time measurements cover the temperature range of 1181–1498 K, with pressures near 0.9, 1.5, and 2.8 atm, and equivalence ratios of 0.5, 1, and 2, in 4% oxygen/argon. The ignition delay time data feature low scatter and can be correlated to a single expression with ² ～ 0.99: τ_ign = 7.30 × 10^{?4 ?0.68} Φ^0.45 exp(18,265/), where τ_ign is in μs, in atm, and in K. OH time histories were measured using laser absorption of the R₁(5) line of the A‐X(0,0) transition near 306.7 nm, in stoichiometric mixtures of 500 ppm DMA/O₂/argon. The mechanism developed by Li et al. was used initially to simulate the measured DMA ignition delay times and the OH time histories. The Li et al. mechanism was then updated by adding the DMA unimolecular decomposition channel: DMA = CH₃NH + CH₃, with the reaction rate constant estimated by analogy to dimethyl ether decomposition, previously investigated by Cook et al. The reactions of DMA + OH were also updated based on recent work in our laboratory. The simulation results using the modified Li et al. mechanism are in good agreement with both the ignition delay times and OH time‐history data.     

Hyperbranched Polymers Formed through Irreversible Step Polymerization of AB2‐Type Monomer in a Continuous Flow Stirred‐Tank Reactor (CSTR)

Hyperbranched polymers formed through step polymerization of AB₂‐type monomer with equal reactivity for both B groups in a continuous flow stirred‐tank reactor (CSTR) are investigated theoretically. The weight fraction distribution at high molecular weight tail follows a power law, W (P ) ∝ P ^−1/ξ for ξ ≤ 0.5 with , where is the mean residence time. The degree of branching (DB) at the large degree of polymerization (P ) limit is DB _{P →∞} = 0.6 irrespective of the ξ‐value, which is larger than the case for the corresponding batch polymerization that gives DB _{P →∞} = 0.5. The relationship between the radius of gyration 〈s ²〉₀ and P shows that the hyperbranched polymers formed in a CSTR are very compact, and the 〈s ²〉₀‐values for large polymers are even smaller than the smallest possible case for a batch reactor with DB _{P →∞} = 1. For large polymers, the power law 〈s ²〉₀∝P ^1/3 holds, which is 〈s ²〉₀∝P ^1/2 for batch polymerization.

     

Supramolecular Assembly of Metal Complexes by (Aryl)I⋅⋅⋅d [PtII] Halogen Bonds

The theoretical data for the half-lantern complexes [{Pt( )(μ- )}₂] [ 1 – 3 ; is cyclometalated 2-Ph-benzothiazole; is 2-SH-pyridine ( 1 ), 2-SH-benzoxazole ( 2 ), 2-SH-tetrafluorobenzothiazole ( 3 )] indicate that the Pt ⋅⋅⋅ Pt orbital interaction increases the nucleophilicity of the outer d orbitals to provide assembly with electrophilic species. Complexes 1 – 3 were co-crystallized with bifunctional halogen bonding (XB) donors to give adducts ( 1 – 3 )₂ ⋅ (1,4-diiodotetrafluorobenzene) and infinite polymeric [ 1⋅ 1,1′-diiodoperfluorodiphenyl]_n. X-ray crystallography revealed that the supramolecular assembly is achieved through (Aryl)I ⋅⋅⋅ d [Pt^II] XBs between iodine σ-holes and lone pairs of the positively charged (Pt^II)₂ centers acting as nucleophilic sites. The polymer includes a curved linear chain ⋅⋅⋅ Pt₂ ⋅⋅⋅ I(arene^F)I ⋅⋅⋅ Pt₂ ⋅⋅⋅ involving XB between iodine atoms of the perfluoroarene linkers and (Pt^II)₂ moieties. The ¹⁹⁵Pt NMR, UV/Vis, and CV studies indicate that XB is preserved in CH(D)₂Cl₂ solutions.     

Pentaatomic planar tetracoordinate silicon with 14 valence electrons: A large‐scale global search of (n + m = 4; q = 0, ±1, −2; X,Y = main group elements from H to Br)

Designing and characterizing the compounds with exotic structures and bonding that seemingly contrast the traditional chemical rules are a never‐ending goal. Although the silicon chemistry is dominated by the tetrahedral picture, many examples with the planar tetracoordinate‐Si skeletons have been discovered, among which simple species usually contain the 17/18 valence electrons. In this work, we report hitherto the most extensive structural search for the pentaatomic ptSi with 14 valence electrons, that is, (n + m = 4; q = 0, ±1, ?2; X, Y = main group elements from H to Br). For 129 studied systems, 50 systems have the ptSi structure as the local minimum. Promisingly, nine systems, that is, , HSiY₃ (Y = Al/Ga), Ca₃SiAl^?, Mg₄Si^2?, C₂LiSi, Si₃Y₂ (Y = Li/Na/K), each have the global minimum ptSi. The former six systems represent the first prediction. Interestingly, in HSiY₃ (Y = Al/Ga), the H‐atom is only bonded to the ptSi‐center via a localized 2c–2e σ bond. This sharply contradicts the known pentaatomic planar‐centered systems, in which the ligands are actively involved in the ligand–ligand bonding besides being bonded to the planar center. Therefore, we proposed here that to generalize the 14e‐ptSi, two strategies can be applied as (1) introducing the alkaline/alkaline‐earth elements and (2) breaking the peripheral bonding. In light of the very limited global ptSi examples, the presently designed six systems with 14e are expected to enrich the exotic ptSi chemistry and welcome future laboratory confirmation. © 2014 Wiley Periodicals, Inc.     

Correlating Boron–Hydrogen Stretching Frequencies with Boron–Hydrogen Bond Lengths in Closoboranes: An Approach Using DFT Calculations

Using harmonic and anharmonic DFT calculations, we have established a general correlation between B–H stretching frequencies and B–H bond lengths valid for the closoboranes (x = 6 – 12), substituted closoboranes B₁₂H_{12 –} (with X = F, Cl, Br and n = 1 – 3 and 9 – 12) and the carboranes and , suggesting that this correlation is also applicable to other similar species. It appears that the average B–H stretching frequency observed around 2500 cm⁻¹ shift by about −100 cm⁻¹ if the average B–H bond length increases by 1 pm. In contrast to , the B–H bond in closoboranes is practically covalent and the correlation evidenced between its stretching frequency and its length proves to be similar to the one observed for the C–H bond.     

LaSr3NiRuO4H4: A 4d Transition‐Metal Oxide–Hydride Containing Metal Hydride Sheets

The synthesis of the first 4d transition metal oxide–hydride, LaSr₃NiRuO₄H₄, is prepared via topochemical anion exchange. Neutron diffraction data show that the hydride ions occupy the equatorial anion sites in the host lattice and as a result the Ru and Ni cations are located in a plane containing only hydride ligands, a unique structural feature with obvious parallels to the CuO₂ sheets present in the superconducting cuprates. DFT calculations confirm the presence of S= Ni⁺ and S=0, Ru²⁺ centers, but neutron diffraction and μSR data show no evidence for long‐range magnetic order between the Ni centers down to 1.8 K. The observed weak inter‐cation magnetic coupling can be attributed to poor overlap between Ni 3d and H 1s in the super‐exchange pathways.     

Universality in Branching Frequencies and Molecular Dimensions during Hyperbranched Polymer Formation: Step Polymerization of AB2 Type Monomer with Equal Reactivity

Hyperbranched polymer formation during step polymerization of AB₂ type monomer with equal reactivity of two B's is investigated theoretically, focusing the attention to the degree of branching (DB) and the mean square radius of gyration for the unperturbed chains, . It is found that the DB‐value at large degree of polymerization (P) limit, = 0.5 is unchanged during the whole course of polymerization. The average value of having the same P is invariant throughout the polymerization. The universal curve between and P agrees perfectly with that for the self‐condensing vinyl polymerization (SCVP), another method to synthesize hyperbranched polymers, when the reactivity ratio for SCVP, r_SCVP, is 2.589 that gives = 0.5. The power law, is found for large values of P.

     

Structure and Composition of the 200 K‐Superconducting Phase of H2S at Ultrahigh Pressure: The Perovskite (SH−)(H3S+)

At ultrahigh pressure (>110 GPa), H₂S is converted into a metallic phase that becomes superconducting with a record T_c of approximately 200 K. It has been proposed that the superconducting phase is body‐centered cubic H₃S (Im m, a=3.089 Å) resulting from the decomposition reaction 3 H₂S→2 H₃S+S. The analogy between H₂S and H₂O led us to a very different conclusion. The well‐known dissociation of water into H₃O⁺ and OH^? increases by orders of magnitude under pressure. H₂S is anticipated to behave similarly under pressure, with the dissociation process 2 H₂S→H₃S⁺+SH^? leading to the perovskite structure (SH^?)(H₃S⁺). This phase consists of corner‐sharing SH₆ octahedra with SH^? ions at each A site (the centers of the S₈ cubes). DFT calculations show that the perovskite (SH^?)(H₃S⁺) is thermodynamically more stable than the Im m structure of H₃S, and suggest that the A site hydrogen atoms are most likely fluxional even at T_c .     

The nature of the chemical bond in borazine (B3N3H6), boroxine (B3O3H3), carborazine (B2N2C2H6), and related species

The bonding problem in borazine (B₃N₃H₆), boroxine (B₃O₃H₃), and carborazine (B₂N₂C₂H₆) is successfully addressed through the consideration of the excited states of the constituent fragments, namely BH( ), NH( ), and CH( ). We propose the participation of resonant structures for all three species that help to explain the experimental findings. A discussion on the chemical pattern of the parental molecule benzene (C₆H₆) helps to make coherent the whole bonding analysis on the titled species.     

A Visible‐Light‐Triggered Conformational Diastereomer Photoswitch in a Bridged Azobenzene

Ketal‐substituted bridged azobenzenes have been synthesized; these display a symmetrical boat conformation with the ketal in pseudo‐equatorial positions. These bridged Z‐azobenzenes (Z₁) readily photoisomerize to the E‐isomer as well as another Z‐conformer (Z₂) with ketal function on the pseudo‐axial position upon irradiation at 406 nm. The two diastereomeric conformers display distinct physicochemical characteristics. Spectroscopic and NMR investigations supported that interconversion of two conformers occurs via the E‐isomer, with good photochemical quantum yield (Φ =0.45±0.03, Φ =0.33±0.05, Φ =0.37±0.06 and Φ =0.36±0.04). The system shows high photostability and no thermal equilibrium between the two stable Z₁ and Z₂ conformers.