Die Gasmolekeln Re3Cl9, Re3Br9 und Re3J9. Halogenaustausch und Fragmentierung

The Gaseous Molecules Re₃Cl₉, and Re₃I₉. Halogen Exchange and Fragmentation The mass spectrum of Re₃I₉ is communicated and compared with the spectra of Re₃Cl₉ and Re₃Br₉. The fragmentation corresponds with the stability of the bonds Re? Cl, Re? I, and Re? Re. In the mixed halides Re₃Cl_9?nX_n (X = Br, I) the observed abundance of molecules with n = 0–9 may be described statistically using the same weight for all the 9 positions of halogen. No difference of the 3 bridging halogens and the 6 terminal halogens can be seen regarding the halogen exchange at 300°C.     

Products of binary complex compounds thermolysis: Catalysts for hydrogen peroxide decomposition

Samples are obtained via the thermolysis of binary complex compounds in a hydrogen atmosphere. Their catalytic activity in hydrogen peroxide decomposition is studied. The values of the rate constants and activation energies for the catalytic reaction are estimated. The correlation between catalytic activity, composition, specific surface area (S _sp), and particle size of the samples is analyzed.     

Efficiency of sensitization of titanium dioxide by adsorbed acridine yellow in photocatalytic hydrogen evolution

Quantum efficiency of the photocatalytic hydrogen evolution upon illumination in the self-and dyesensitized absorption bands of suspended titanium dioxide has been determined. The photocatalytic activity observed upon illumination in the sensitization band is shown to be due to absorption of light quanta by adsorbed molecules of the dye.

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Theoretical Investigation of the Stepwise Hydrolysis of the [Re3(μ‐Cl)3Cl9]3‐ Anion

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Pressure tuning of electronic states of Cs3Re3Cl12

The pressure shifts of three metal π→π transitions in Cs₃Re₃Cl₁₂ have been measured up to 110 kbar. A comparison of the shifts gives, for the first time, the relative stabilization between a pair of unoccupied antibonding molecular orbitais and between a pair of occupied bonding molecular orbitals as a function of pressure. The results are discussed in terms of the atomic parentage of these molecular orbitals.     

Quantification of hydrogen peroxide during the low-temperature oxidation of alkanes

The first reliable quantification of hydrogen peroxide (H(2)O(2)) formed during the low-temperature oxidation of an organic compound has been achieved thanks to a new system that couples a jet stirred reactor to a detection by continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near-infrared. The quantification of this key compound for hydrocarbon low-temperature oxidation regime has been obtained under conditions close to those actually observed before the autoignition. The studied hydrocarbon was n-butane, the smallest alkane which has an oxidation behavior close to that of the species present in gasoline and diesel fuels.     

High-temperature X-ray diffraction study of thermolysis of the double complex salt [Rh(NH3)5Cl][PtCl4]

The formation process of a nanosize powder of the equilibrium solid solution Pt_0.50Rh_0.50 by thermolysis of the double complex salt [Rh(NH₃)₅Cl][PtCl₄] under hydrogen or helium and in vacuo was studied in situ by X-ray diffraction and synchrotron radiation. The reduction temperature of the metals in the cationic and anionic moieties of the starting complex is the main factor responsible for the mechanism of solid solution formation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1069–1073, July, 2006.     

Die Kristallstruktur von SCl3[Re2Cl9] und ihre Verwandtschaft zum RuBr3‐Typ

The Crystal Structure of SCl₃[Re₂Cl₉] and its Relation to the RuBr₃ Type SCl₃[Re₂Cl₉] was obtained from the reaction of rhenium and SCl₂ at 400 °C. The X‐ray crystal structure determination revealed a monoclinic structure, a = 834.1 pm, b = 1053.3 pm, c = 866.1 pm, β = 91.90°, space group P2₁/m, R₁ = 0.058. The SCl₃⁺ and Re₂Cl₉^– ions have the known structures; the ReRe bond length in the face‐sharing bioctahedron is 272.2 pm. The crystal packing can be derived from the RuBr₃ structure type, which has infinite columns of face‐sharing octahedra; one quarter of the metal atoms are removed and another quarter are replaced by sulfur atoms. The chlorine atoms form a slightly distorted hexagonal closest‐packing. The symmetry relationships are shown in a family tree of group–subgroup relations.     

Intercalation of Re(phen)(CO)3Cl into zirconium phosphate: a water insoluble inorganic complex immobilized in a highly polar rigid matrix

The intercalation of fac-tricarbonylchloro-1,10-phenanthrolinerhenium(i) (Re(phen)(CO)(3)Cl) within zirconium phosphate (ZrP) has been achieved using a hydrated ZrP phase that possesses six water molecules per formula unit. This intercalation occurs only at high solution molar ratios (Re : ZrP, 3 : 1) and is characterized by the emergence of a new phase in the X-ray powder diffraction (XRPD) pattern with an interlayer distance of 15.6 A. The XRPD patterns show a decrease in the crystallinity upon intercalation of the inorganic complex. The MLCT absorption bands of Re(phen)(CO)(3)Cl-containing ZrP materials are red shifted in comparison with the complex in acetonitrile whilst the luminescence spectra at different loading levels are blue shifted up to 30 nm in comparison with the complex in acetonitrile. This blue shift is consistent with the rigidochromic effect. The luminescence lifetime of Re(phen)(CO)(3)Cl within ZrP was increased in comparison with its lifetime in acetonitrile solution but is shorter than that of Re(phen)(CO)(3)Cl in frozen glass and polyesther resins. To our knowledge, this is the first example of a water insoluble metal complex intercalated within the layers of ZrP, which opens up new possibilities in the intercalation chemistry of this lamellar material and in the study of host-guest interactions.     

Synthesis and Crystal Structure of (PCl4)[Re2Cl9]

The reaction between PCl₃ and ReCl₅ yielded at 200 °C the ionic tetrachlorophosphonium dirhenium nonachloride, (PCl₄)[Re₂Cl₉]. Single crystal X-ray diffraction analysis revealed a monoclinic unit cell: a = 8.616(3) Å, b = 10.449(4) Å, c = 9.397(3) Å, β = 99.72(3)°, V = 833.9(5) ų, Z = 2, sp. gr. P2₁/m, wR₂ = 0.1083 and R₁ = 0.0527. The ionic compound is built from tetrahedra PCl₄⁺ and face-sharing bioctahedra Re₂Cl₉^–. The Re–Re distance, 2.724 Å, indicates the presence of direct Re-Re interaction.     

硫缺陷型In2S3光催化剂高效分解水制氢研究

缺陷工程被认为是提高光催化剂分解水制氢性能的关键策略之一,然而有关缺陷诱导半导体材料电子结构演变并增强光生载流子传输机制尚不明确。在本研究中,我们通过简单的一步水热合成法成功构建了富含S缺陷的In2S3半导体光催化剂（VS-In2S3）,在模拟太阳光辐照下其光催化分解水产氢性能相比传统的In2S3（P-In2S3）提升了近一个数量级（达到221.18 μmol/g/h）。此外,利用自主研发的原位X射线光电子能谱（SI-XPS）结合相关密度泛函理论计算证实：S缺陷可诱导强还原性的低价态In（In(3-x)+）暴露,进而增强In位点对H2O的吸附和活化能力,因此,S缺陷型In2S3表现出显著增强的光催化析氢活性。此外,可视化观测到H2O分子在原位光照下脱质子转化为OH的分解水制氢过程。该研究为缺陷型光催化剂设计及光催化分解水反应机制和过程研究提供了一定的见解。     

Reliable determination of oxygen and hydrogen isotope ratios in atmospheric water vapour adsorbed on 3A molecular sieve

The isotope ratio of atmospheric water vapour is determined by wide-ranging feedback effects from the isotope ratio of water in biological water pools, soil surface horizons, open water bodies and precipitation. Accurate determination of atmospheric water vapour isotope ratios is important for a broad range of research areas from leaf-scale to global-scale isotope studies. In spite of the importance of stable isotopic measurements of atmospheric water vapour, there is a paucity of published data available, largely because of the requirement for liquid nitrogen or dry ice for quantitative trapping of water vapour. We report results from a non-cryogenic method for quantitatively trapping atmospheric water vapour using 3A molecular sieve, although water is removed from the column using standard cryogenic methods. The molecular sieve column was conditioned with water of a known isotope ratio to 'set' the background signature of the molecular sieve. Two separate prototypes were developed, one for large collection volumes (3 mL) and one for small collection volumes (90 microL). Atmospheric water vapour was adsorbed to the column by pulling air through the column for several days to reach the desired final volume. Water was recovered from the column by baking at 250 degrees C in a dry helium or nitrogen air stream and cryogenically trapped. For the large-volume apparatus, the recovered water differed from water that was simultaneously trapped by liquid nitrogen (the experimental control) by 2.6 per thousand with a standard deviation (SD) of 1.5 per thousand for delta(2)H and by 0.3 per thousand with a SD of 0.2 per thousand for delta(18)O. Water-vapour recovery was not satisfactory for the small volume apparatus.     

Nitride formation by thermolysis of a kinetically stable niobium dinitrogen complex

The reduction of [P(2)N(2)]NbCl (where [P(2)N(2)] = PhP(CH(2)SiMe(2)NSiMe(2)CH(2))(2)PPh) with KC(8) under a dinitrogen atmosphere generates the paramagnetic dinuclear dinitrogen complex ([P(2)N(2)]Nb)(2)(mu-N(2)) (2). Complex 2 has been characterized crystallographically and by EPR spectroscopy. Variable-temperature magnetic susceptibility measurements indicate that 2 displays antiferromagnetic coupling between two Nb(IV) (d(1)) centers. A density functional theory calculation on the model complex [(PH(3))(2)(NH(2))(2)Nb](2)(mu-N(2)) was performed. Thermolysis of ([P(2)N(2)]Nb)(2)(mu-N(2)) in toluene generates the paramagnetic bridging nitride species where one N atom of the dinitrogen ligand inserts into the macrocycle backbone to form [P(2)N(2)]Nb(mu-N)Nb[PN(3)] (3) (where [PN(3)] = PhPMe(CHSiMe(2)NSiMe(2)CH(2)P(Ph)CH(2)SiMe(2)NSiMe(2)N)). Complex 3 has been characterized in the solid state as well as by variable-temperature magnetic susceptibility measurements. The reaction of ([P(2)N(2)]Nb)(2)(mu-N(2)) with phenylacetylene displaces the dinitrogen fragment to generate a paramagnetic eta(2)-alkyne complex, [P(2)N(2)]Nb(eta(2)-HCCPh) (4).     

Theoretical investigation of the stepwise hydrolysis of the [Re(3)(mu-Cl)(3)Cl(9)](3-) anion

A detailed study of the stepwise substitution of the chloride ligands in the [Re3(mu-Cl)3Cl9](3-) (1) anion by water molecules is presented using theoretical methods. Ligand lability as well as the structure and relative stability of the various mono-[Re3(mu-Cl)3Cl8(H2O)](2-) (2a,b) and dihydro-[Re3(mu-Cl)3Cl7(H2O)2](-) (3a-f) conformers is examined. Clear preferences for the positions of the incoming water ligands are proposed based on calculated energy and vibrational data, which fully agree with the experimental results.     

Sims analysis of the distribution of hydrogen absorbed by gold electrodes during the evolution of hydrogen

Gold electrodes were charged with hydrogen by strong cathodic treatment in 0.5 M H₂SO₄. The concentration of hydrogen was then studied by SIMS both along the surface and in depth by etching in the ion beam. With electrodes consisting of a small number of crystals, the absence of abnormal hydrogen concentration at the grain boundaries seems to rule out diffusion along this route. The profiles observed seem to be consistent with a simple model of uniform bulk diffusion.     

Valence-Dependent Metal-Metal Bonding and Optical Spectra in Confacial Bioctahedral [Re(2)Cl(9)](z)()(-) (z = 1, 2, 3). Crystallographic and Computational Characterization of [Re(2)Cl(9)](-) and [Re(2)Cl(9)](2)(-)

The geometric structure of the confacial bioctahedral [Re(2)Cl(9)](z)()(-) anion has been determined by single-crystal X-ray diffraction in two distinct oxidation states, Re(IV)(2) and Re(III)Re(IV). [Bu(4)N][Re(2)Cl(9)] crystallizes in the monoclinic space group P2(1)/m [a/? = 10.6363(3), b/? = 11.420(1), c/? = 13.612(1), beta/deg = 111.18(1), Z = 2], while [Et(4)N](2)[Re(2)Cl(9)] crystallizes in the orthorhombic space group Pnma [a/? = 15.82(1), b/? = 8.55(2), c/? = 22.52(3), Z = 4]. The Re-Re separation contracts from 2.704(1) ? in [Bu(4)N][Re(2)Cl(9)] to 2.473(4) ? in [Et(4)N](2)[Re(2)Cl(9)] (or, equivalently, from 2.725 to 2.481 ? after standard corrections for thermal motions), while the formal metal-metal bond order falls from 3.0 to 2.5. SCF-Xalpha-SW molecular orbital calculations show that, despite the {d(3)d(3)} configuration, the single sigma bond in [Re(2)Cl(9)](-) dominates the observed structural properties. For [Re(2)Cl(9)](2)(-), the 0.23 ? contraction in Re-Re is attributed jointly to radial expansion of the Re 5d orbitals and to diminished metal-metal electrostatic repulsion, which act in concert to make both sigma and delta(pi) bonding more important in the reduced species. Computed transition energies and oscillator strengths for the two structurally defined anions permit rational analysis of their ultraviolet spectra, which involve both sigma --> sigma and halide-to-metal change-transfer absorptions. The intense sigma --> sigma band progresses from 31 000 cm(-)(1) in [Re(2)Cl(9)](-) to 36 400 cm(-)(1) in [Re(2)Cl(9)](2)(-), according to the present assignments. For electrogenerated, highly reactive [Re(2)Cl(9)](3)(-) (where conventional X-ray structural information is unlikely to become available), the dominant absorption band advances to 40 000 cm(-)(1), suggesting further strengthening of the metal-metal sigma bond in the Re(III)(2) species.