Specific features of the reactions of 2,3-dichloro-1-propene with dibenzylchalcogenides in the system hydrazine hydrate-alkali

Dibenzyldisulfide and -diselenide react with 2,3-dichloro-1-propene in the system hydrazine hydrate-KOH by the domino mechanism: nucleophilic substitution of the allyl chlorine, dehydrochlorination with participation of the chlorine atom at the sp ²-carbon atom, allene-acetylene rearrangement, nucleophilic addition of the chalcogenide reagent to the triple bond. The effect of the nature of the chalcogen atom and the benzyl substituent on the studied domino reaction is discussed.     

原子转移自由基聚合引发体系的最新研究进展

本文介绍了关于原子转移自由基聚合（ATRP）引发-活化-失活过程的最新研究情况,包括RATRP、SR&NI ATRP、AGET ATRP、ARGET ATRP以及ICAR ATRP等新型ATRP引发体系。这些新型ATRP体系逐渐克服了通常ATRP体系的局限性,尤其是后两种体系仅需微量（1～50 ppm）价态稳定的过渡金属络合物调控聚合,大大简化了ATRP方法的工业化生产程序;本文同时介绍了杂化及双金属ATRP催化体系,这两种新型催化体系具有较高的催化活性和对聚合反应的调控能力,而且通过简单地过滤或沉降就可从聚合产物当中脱除。     

金属复合催化剂对煤气化的暂态动力学研究

采用阶跃扰动技术进行了金属复合催化剂对煤气化的暂态动力学研究。根据实验结果推导得出了该反应过程是催化剂表面富氧活性部位先与煤焦反应生成一个CO分子，然后此CO分子从催化剂表面脱附，接着催化剂吸附气态的CO2生成一个CO并且夺得一个氧原子实现自身还原的过程，在此基础上建立了煤的催化气化的物料平衡方程组，对各步骤的反应速率常数进行了求解，在本文采用的实验条件下，各反应步骤的反应速率常数分别为0.0703 mol·g-1·min-1·kPa-1;0.0959 mol·g-1·min-1·kPa-1;0.00539 mol·g-1·min-1·kPa-1; 0.0321mol·g-1·min-1·kPa-1。由此得出了该反应历程的控制步骤为CO2的吸附步骤等历程信息。     

Catalytic Properties of Polymer-bound Imine Copper(Ⅱ) Complex

As heterogeneous catalyst, polymer metal complexes is stable in air, low corrosive, low toxic, easy to separate and reclaim,1,2 which superior than organic metal low-molecular complexes, so be paid close attention since 1960' and apply in industry gradually. There are many reports in polymer metal catalyst which is used in oxidation and hydrogenation3 In this paper, complexes of Cu(II) with polymer schiff base ligand: poly (dinitrobenzaldehyde aminating styrene)-Cu(PDNBA-Cu), poly(m-nitrobenzaldehyde aminating styrene)-Cu(PMNBA-Cu), poly(dihydroxybenzaldehyde aminating styrene)Cu(PDHBA-Cu), PDNBA-Cu-Phen were synthesized and characterized by FT-IR, XPS, GC-MS and element analysis. The results show that oxygen atom of hydroxide radical and nitrogen atom are both coordinating with Cu2+ and N:Cu≈ 1: 1. The results also show the complexes are well stability.     

Au-catalyzed tandem cyclization/[1,2]-alkyl migration reaction of epoxy alkynes: synthesis of spiropyranones

A novel gold-catalyzed tandem cyclization/[1,2]-alkyl migration process of epoxy alkynes to spiropyranones has been discovered. From this process, the construction of adjacent multiple stereocenters with a new quaternary carbon atom is achieved. The gold-catalyzed domino process is stereospecific with respect to the migrating carbon atom. A type of unusual C-C bond cleavage of epoxide systems has also been discovered, which can lead to the formation of two Z alkenes and a carbonyl functional group in one step with excellent stereoselectivity. Furthermore, this efficient domino process could be achieved in the presence of the simplest and least expensive gold catalyst [NaAuCl(4)].2H(2)O with a low catalyst loading.     

Alkynes as synthetic equivalents to stabilized Wittig reagents: intra- and intermolecular carbonyl olefinations catalyzed by Ag(I), BF3, and HBF4

[reaction: see text] The first use of cationic silver (AgSbF4) as a catalyst for intra- and intermolecular alkyne-carbonyl coupling to form conjugated enones is described, and a comparison to corresponding Br?nsted acid (HBF4) and Lewis acid (BF3) catalyst systems is made. Notably, intermolecular coupling proceeds stereoselectively to afford the corresponding trisubstituted enones as single geometrical isomers. This transformation represents a completely atom economical alternative to the use of stabilized Wittig reagents in carbonyl olefination and may be viewed as a formal alkyne-carbonyl metathesis.     

The Influence of Activating Agents on the Controlled Synthesis of Poly(methyl methacrylate) in the Presence of Ruthenacarboranes

The radical polymerization of methyl methacrylate catalyzed by systems based on the carborane complexes of ruthenium(III) is studied in the presence of a number of activating agents: tin 2-ethyl hexanoate, aluminum isopropoxide, isopropylamine, and AIBN. It is shown that in the presence of the systems under consideration, polymerization proceeds in a controlled mode via the ATRP mechanism (AGET or ICAR ATRP) at catalyst concentrations with ppm level relative to that of the monomer. As the degree of monomer conversion grows, the molecular weight of the polymer increases linearly while its polydispersity coefficients decrease linearly. The role of the mentioned agents is to transfer the catalyst to the active form containing a metal atom in the oxidation number +2 and able to interact with halogen-terminated dormant polymer chains. It is first shown that the carborane complexes of ruthenium(II) are applicable for the catalysis of controlled radical polymerization.     

Amide‐Substituted Titanocenes in Hydrogen‐Atom Transfer Catalysis

Two new catalytic systems for hydrogen‐atom transfer (HAT) catalysis involving the N?H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtree's catalyst to yield an efficient bimetallic system for radical generation and HAT catalysis.     

Photocatalytic hydrogen evolution from FeMoS-based biomimetic chalcogels

The naturally abundant elements used to catalyze photochemical processes in biology have inspired many research efforts into artificial analogues capable of proton reduction or water oxidation under solar illumination. Most biomimetic systems are isolated molecular units, lacking the protective encapsulation afforded by a protein's tertiary structure. As such, advances in biomimetic catalysis must also be driven by the controlled integration of molecular catalysts into larger superstructures. Here, we present porous chalcogenide framework materials that contain biomimetic catalyst groups immobilized in a chalcogenide network. The chalcogels are formed via metathesis reaction between the clusters [Mo(2)Fe(6)S(8)(SPh)(3)Cl(6)](3-) and [Sn(2)S(6)](4-) in solution, yielding an extended, porous framework structure with strong optical absorption, high surface area (up to 150 m(2)/g), and excellent aqueous stability. Using [Ru(bpy)(3)](2+) as the light-harvesting antenna, the chalcogels are capable of photocatalytically producing hydrogen from mixed aqueous solutions and are stable under constant illumination over a period of at least 3 weeks. We also present improved hydrogen yields in the context of the energy landscape of the chalcogels.     

Structural Characterization of Non-Oxide Chalcogenide Glasses using Solid State NMR

In spite of the long-standing importance of non-oxide chalcogenide glasses in infrared optics and semiconductor technology, concepts describing the structural principles governing glass formation in these systems are just emerging. Most recently, modern quantitative solid state NMR techniques have offered new unique insights into the structural organization of these systems. In this review, we discuss the basic principles of various experimental approaches and their application to boron-silicon, -and phosphorus chalcogenide glasses.     

Novel synthesis of a highly active carbon-supported Ru85Se15 chalcogenide catalyst for the oxygen reduction reaction

A carbon-supported Ru₈₅Se₁₅ chalcogenide catalyst was synthesized via a microwave-assisted polyol process using RuCl₃ and Na₂SeO₃ as the Ru and Se precursors. The Ru₈₅Se₁₅ chalcogenide catalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively-coupled plasma-atomic emission spectroscopy (ICP-AES). The XRD pattern for Ru₈₅Se₁₅/C clearly exhibited the characteristic reflections of metallic ruthenium. The TEM image indicated that the Ru₈₅Se₁₅ chalcogenide catalyst was well dispersed on the surface of the carbon support with a narrow particle size distribution. Rotating disk electrode (RDE) and single-cell measurements were carried out to evaluate the electrocatalytic activity of the Ru₈₅Se₁₅ chalcogenide catalyst. The oxygen reduction reaction (ORR) activity of the Ru₈₅Se₁₅/C catalyst was compared with the commercial Pt/C catalyst with the absence/presence of methanol. In the absence of methanol, the Ru₈₅Se₁₅/C catalyst showed a comparable ORR activity with the Pt/C catalyst. However, in the presence of methanol, the Ru₈₅Se₁₅/C catalyst showed a better ORR activity than the Pt/C catalyst. The performance of the membrane electrode assembly (MEA) prepared with Ru₈₅Se₁₅/C as the cathode catalyst in a single proton exchange membrane fuel cell (PEMFC) showed the maximum power density of 400 mW cm⁻² at the current density of 1300 mA cm⁻².     

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N‐Heterocyclic Carbene Precursors for Atom‐Economic Amide Synthesis from Alcohols and Amines

The transition‐metal‐catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom‐economic process. Among various catalyst systems, in situ generated N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron‐deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR‐scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=?7.8 ppm in the ¹H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system.     

Selective deoxygenation of sugar polyols to alpha,omega-diols and other oxygen content reduced materials--a new challenge to homogeneous ionic hydrogenation and hydrogenolysis catalysis

An oxygen atom on every carbon--this is the problem! While nature provides linear C(3) to C(6) building blocks in the form of sugar alcohols in large and renewable abundance, they are overfunctionalized for the purpose of most chemical applications. Selective deoxygenation by anthropogenic catalyst systems may be one answer to this challenge.     

Reaction conducted under rather severe conditions for a colloidal catalyst - hydroformylation of propylene catalyzed by polymer-protected rhodium colloids

Hydroformylation of propylene has been conducted by a polymer-protected rhodium colloid catalyst with an activity of 130 mol butanal / g atom Rh·h. The neat colloid catalyst is stable enough for repeated use for 7 times lasting ∼50 h under the reaction condition (temperature: 363 K, pressure: 40 bar) with a total TON of 5,065 cycle / atom Rh.     

Solvent‐driven symmetry of self‐assembled nanocrystal superlattices—A computational study

The preference of experimentally realistic sized 4‐nm facetted nanocrystals (NCs), emulating Pb chalcogenide quantum dots, to spontaneously choose a crystal habit for NC superlattices (Face Centered Cubic (FCC) vs. Body Centered Cubic (BCC)) is investigated using molecular simulation approaches. Molecular dynamics simulations, using united atom force fields, are conducted to simulate systems comprised of cube‐octahedral‐shaped NCs covered by alkyl ligands, in the absence and presence of experimentally used solvents, toluene and hexane. System sizes in the 400,000–500,000‐atom scale followed for nanoseconds are required for this computationally intensive study. The key questions addressed here concern the thermodynamic stability of the superlattice and its preference of symmetry, as we vary the ligand length of the chains, from 9 to 24 ? CH₂ groups, and the choice of solvent. We find that hexane and toluene are “good” solvents for the NCs, which penetrate the ligand corona all the way to the NC surfaces. We determine the free energy difference between FCC and BCC NC superlattice symmetries to determine the system's preference for either geometry, as the ratio of the length of the ligand to the diameter of the NC is varied. We explain these preferences in terms of different mechanisms in play, whose relative strength determines the overall choice of geometry. © 2012 Wiley Periodicals, Inc.     

Asymmetric Rhodium‐Catalyzed Addition of Thiols to Allenes: Synthesis of Branched Allylic Thioethers and Sulfones

A highly regio‐ and enantioselective hydrothiolation of terminal allenes, a reaction which fulfills the criteria of atom economy, is reported. Applying two chiral rhodium catalyst systems, a wide variety of thiols and allenes could be coupled. Oxidation gave access to the corresponding allylic sulfones in essentially enantiomerically pure form. The reaction tolerates a variety of functional groups and labeling experiments gave first insights into the reaction mechanism of this new methodology.     

乙烷在Pt/γ-Al2O3（001）模型催化剂上吸附行为的理论研究

本文采用密度泛函理论方法和周期性边界条件,考察了Pt原子与γ-Al2O3(001)表面上六种不同位点的相互作用,获得了最稳定吸附位的Pt/γ-Al2O3模型催化剂,建立了Pt原子负载在γ-Al2O3(001)表面的模型催化剂。同时,考查了乙烷分子在Pt/γ-Al2O3模型催化剂上的吸附行为。结果表明,在Pt/γ-Al2O3模型催化剂上,Pt原子转移了部分电子到载体γ-Al2O3。乙烷以分子态形式吸附在Pt/γ-Al2O3模型催化剂上,靠近Pt原子的C-H键受到一定程度地活化。     

Synthesis of lead chalcogenide nanocrystals by sequential ion implantation in silica

Lead chalcogenide (PbS, PbSe, and PbTe) nanocrystals were synthesized by sequential implantation of Pb and one of the chalcogen species into pure silica. The implantation energy and fluence were chosen so that the implantation profiles practically overlap at a depth approximately 150 nm with a maximum concentration of about 0.3 atom %. Annealing for 1-8 h at 850-900 degrees C triggers nanocrystal growth, which is monitored by high-resolution (HRTEM) and conventional transmission electron microscopy (TEM), secondary-ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). Striking differences are found in the depth distributions and microstructures of the resulting nanocrystals. We show that the differing chemical interactions of Pb and chalcogens (between each other and with silica) play a crucial role in chalcogenide nucleation and growth. Using available information on chalcogen redox states in silicate glass, we propose a nonclassical nucleation and growth mechanism consistent with our experimental results. The complex chemistry involved at the microscopic level is shown to impair control over the nanocrystal size distribution. Finally, PbS nanocrystal-doped silica is shown to emit intense photoluminescence (PL) in the 1.5-2 microm wavelength range, an effect that we relate to the above nucleation and growth scheme.     

Analytical characteristics and sensitivity mechanisms of electrolyte-insulator-semiconductor system-based chemical sensors—a critical review

Recent trends in research and development of electrolyte-insulator-semiconductor (EIS) field-effect chemical sensors (ion-selective field-effect transistors, light-addressable potentiometric sensors, capacitive EIS-sensors) with inorganic gate insulators (oxide, nitride and chalcogenide films) are reviewed. Physical properties of EIS systems and basic mechanisms of their chemical sensitivity are examined. Analytical characteristics and sensing mechanisms of EIS pH sensors with oxide and nitride films, as well as metal ions sensors with chalcogenide films, are critically discussed. Prospects of future research on EIS field-effect biosensors are briefly outlined.     

Chemical sensors with chalcogenide glassy membranes

The present review is emphasized on the recent achievements in the application of chalcogenide glasses (ChG) as membrane materials in chemical sensors, microsensors and multisensor systems. The questions concerning material synthesis, sensor designs and the concepts for the potential-generating mechanisms have briefly discussed. Most of the chalcogenide glass-forming systems and compositions investigated as membrane active materials have been summarized, and their analytical characteristics have been considered. The efficiency of chalcogenide-based chemical sensors in the real system analyses, as well as the advantages and disadvantages in their analytical performance have been evaluated and compared with the corresponding polycrystalline analogous.