Photocatalysis of Chloroform Decomposition by the Hexachlororuthenate(IV) Ion

Dissolved hexachlororuthenate(IV) effectively catalyzes the photodecomposition of chloroform to hydrogen chloride and phosgene under near‐UV (λ > 345 nm) irradiation, whereby RuCl₆^2? is not itself photocatalytically active, but is photochemically transformed into a species that is active, possibly RuCl₅(CHCl₃)^?. Conversion to a photoactive species during irradiation is consistent with the acceleration of the decomposition rate during the early stages and with the apparent inverse dependence of the decomposition rate on the initial concentration of RuCl₆^2?. The displacement of Cl^? by CHCl₃ in the coordination sphere to create the photoactive species is consistent with the retardation of photodecomposition by both Cl^? and H₂O. The much smaller photodecomposition rate in CDCl₃ suggests that C–H bond dissociation occurs during the primary photochemical event, which is also consistent with the presence of a CHCl₃ molecule in the first coordination sphere.     

Photocatalysis of Chloroform Decomposition by Tetrachlorocuprate (II) on Dowex 2‐X8

Heterogenized on a polystyrene anion exchange resin and in the presence of oxygen, catalyzes the photodecomposition of chloroform at wavelengths above 345 nm with greater efficiency than an equivalent amount in homogeneous solution. The reaction is proposed to proceed in two stages, the first stage yielding CCl₄ and as products, the second consisting of a chain reaction resulting from the ‐catalyzed photodissociation of CCl₄, yielding phosgene with CCl₃ radicals as chain carriers. Photodecomposition is retarded by added Cl^?, CH₃CN, C₆H₁₂ or C₂H₅OH, which is ascribed to the displacement of CHCl₃ molecules from the vicinity of the copper by attraction to the polystyrene matrix or to the alkylammonium cation sites.     

光催化下(-)-马鞭烯酮的重排

( )-马鞭烯酮[( )-Verbenone]是Wender研究组全合成紫杉醇(Taxol)的重要起始物．( )-马鞭烯酮可由( )-α-蒎烯在Co(Ⅱ)催化下氧化得到,并且在光照下重排得到( )-菊花烯酮[( )-Chrysanthenone]．但从( )-α-蒎烯到( )-菊花烯酮的总产率较低,约为16．5％．我们在重复由光活性α-蒎烯出发经过光活性马鞭烯酮及菊花烯酮衍生物合成紫杉醇AB环的实验中发现,由α-蒎烯合     

Synthesis, Structure, and Thermal Decomposition of Chloropentamminerhodium(III) Hexabromoplatinate(IV)

The binary complex salt [Rh(NH₃)₅Cl][PtBr₆] was synthesized and studied by Xray structural analysis. The crystallographic data are as follows: a = 12.013(2) , b = 8.401(2) , c = 15.999(3) , = 91.13(3)°, V = 1614.3(6) ³, space group P2₁/m, Z = 4, d_x = 3.70 g/cm³, R = 0.086. The thermal decomposition of the salt in a hydrogen atmosphere is shown to produce a Rh_0.5Pt_0.5 solid solution with an FCC cell [a = 3.864(2) . The thermal decomposition of the salt in a helium atmosphere proceeds via the formation of metallic Pt and RhBr₃ and finally results in a mixture of several solid solutions.     

Vanadium-based Mixed Oxides Prepared from Thermal Decomposition of Citratorvanadium(IV) Precursor

Citrate method is broadly used for the preparation of mixed oxides and their highly dispersive pure phases^[1]. Up to now, most of the mixed oxides are prepared from putting the related chemical compounds together and sintering the mixture at high temperature, while the complexes formed during this process are uncertain. This will limit the design of high dispersibility and the purities of the resulted mixed oxides. Vanadium-based oxides are catalysts used in the partial oxidation of propane and butane. It has been demonstrated previously that the vanadium citrate complex with well-defined composition and structure is the better precursors for the preparation of V-based mixed oxide^[2], Using the precursor of barium dimeric(citrato) oxovanadium(IV) tetrahydrates Ba₂[VO(cit)]₂·4H₂O, barium pyrovanadate may be prepared with pre-determinated compositions and higher purities from thermal decomposition of the well-defined complexes at lower temperature.     

Photocatalysis (V) cyclotrimerisation of cycloheptene

When copper(I) triflate·cis-cycloheptene is irradiated in solution, a complex copper(I) triflate·trans-cycloheptene is formed. From the latter compound an all-trans cyclic trimer is formed in 80% yield in a thermal reaction. The mechanism of this cyclotrimerisation is discussed.     

Oxidative breakdown of polymeric plutonium(IV) hydroxide by cerium(IV)

The breakdown of polymeric plutonium(IV) hydroxide (plutonium colloid) by cerium(IV) has been studied spectrophotometrically by monitoring the formation of plutonium(VI). Reaction rate variations were studied with changes in cerium(IV), acid and plutonium colloid concentrations. A reaction mechanism involving the formation of [Ce₂O(OH)₂]⁴⁺ and its reaction with the polymer surface to produce two plutonium(V) ions is postulated to explain the observed kinetic data, in particular the maximum in the reaction rate at around 0.3 M nitric acid.     

Determination of selenium(IV) and tellurium(IV) by differential pulse polarography

Differential pulse polarographic methods for the determination of selenium(IV) and tellurium(IV) in nitric acid medium are described. The peak current is maximal when 0.25M nitric acid medium is used, the DPP peaks for Se(IV) and Te(IV) being at -0.54 and -0.8 V vs. Ag/AgCl respectively. The peak current is a linear function of selenium concentration over three ranges, 5.1 x 10(-6)-1.3 x 10(-5), 1.27 x 10(-5)-1.27 x 10(-4) and 1.27 x 10(-4)-7.60 x 10(-4)M Se(IV), with different slopes. The plot for Te(IV) is linear over the range 0.78 x 10(-6)-9.40 x 10(-5)M.     

可见光催化C(sp3)-C(sp3)键的构筑

本文对近年来可见光催化构筑C(sp ³)-C(sp ³)键的国内外最新研究成果进行概述,着重阐述了各类催化的催化体系、反应机理及在合成生物活性分子或药物分子方面的应用。在可见光催化的反应体系中引入过渡金属或手性催化剂,构建新颖的协同催化体系,可以实现在温和的条件下对C—C键构筑的精确控制,对于手性药物的设计、开发具有重要的意义。最后,对未来可见光催化构筑C—C键的发展进行展望。     

On the stabilization of niobium(V) solutions by zirconium(IV) and hafnium(IV)

Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as chloride and sulphate. This is ascribed to the co-polymerization of niobium(V) and the hydrolysed ionic species of zirconium(IV) and hafnium(IV) to form colloidal particles. In hydrochloric acid the particles are positively charged, whereas in sulphate solution the Zr-and Hf-sulphate complexes confer a negative charge. The two cases are considered separately.     

Complexation and Intramolecular Redox Decomposition of Cerium(IV) Hydroxo Complexes with Oxycarboxylic Acids

Spectrophotometry, pH-metry, and kinetic method were applied to study the complexation and redox decomposition of cerium hydroxo complexes formed in the systems Ce^{4 +}-SO₄ ^2--H _m L, where H _m L (m = 2, 3, 4) are, respectively lactic, malic, and tartaric acids.     

Comparative Study on the Decomposition of Chloroform in Thermal and Cold Plasma

Decomposition of trichloromethane (chloroform, CHCl₃) has been studied in inductively coupled RF thermal plasma and in cold plasma, i.e. in silent electric discharge, in neutral and oxidative conditions, as well. GC--MS analysis of the gaseous products and the extracts of the soots were performed and resulted in the formation of solid soot, aliphatic dienes, cyclo-dienes and some aromatic compounds in neutral conditions of RF thermal plasma. In oxidative conditions, however, much less soot and dienes, and much more oxygen-containing products were formed as compared to neutral ones. In the cold plasma reactor, wide range of chlorinated ethane, ethene and propene derivatives were formed in neutral conditions. In oxidative conditions, formation of carbonyl compounds and carbon monoxide as intermediates took place, while the final product consisted of CO₂, H₂O and Cl₂ in the low temperature plasma reactor.     

Kinetics and mechanism of osmium(VIII) catalyzed oxidation of tellurium(IV) by cerium(IV)

The reaction is first order in substrate and catalyst and zero order in cerium(IV). The rate decreases with increasing [H⁺] as well as with increasing ionic strength. H and S have been found to be 44.8 kJ mol^–1 and 161.8 JK^–1 mol^–1 respectively. A mechanism is proposed.

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(IV). [H⁺], . , H S 44,8 ·^–1 161,8 ·^–1–1, . .

     

Oxopentacyano-complexes of molybdenum(IV) and tungsten(IV) in photolysis of octacyanometalates(IV)

Summary Ligand-field (LF) photolysis of aqueous alkaline solutions of K₄[M(CN)₈] (M = Mo or W) containing KCN produces [MO(CN)₅]^3– species. NaCs₂]MO(CN)₅] was isolated and characterised by u.v.-vis., i.r. and Raman spectroscopy. In addition, the reactions of [MO(OH)(CN)₄]^3– with free CN^– are described and the relations between octa-, penta- and tetra-cyanocomplexes are summarised.