Formation of azatitanacyclopentanes from ene-imines and a Ti(O-i-Pr)4/2i-PrMgX reagent and their synthetic reactions

ω-Vinylimines reacted with a Ti(O-i-Pr)₄/2i-PrMgX reagent to generate the corresponding azatitanacyclopentanes in quantitative yield, which in turn reacted with H₂O, I₂ and O₂ to give 2-methyl-, 2-iodomethyl-, 2-hydroxymethyl-1-aminocyclic compounds, respectively. The azatitanacyclopentanes thus generated reacted with formaldehyde to afford the corresponding 2,3-annulated pyrrolidines in good yield.     

Silica-Based and Transition Metal-Based Inorganic-Organic Hybrid Materials—A Comparison

Organically substituted metal alkoxides can be prepared by reaction of the parent alkoxides with complexing organic compounds. The chemical and structural consequences of such substitutions are discussed in this article. Examples are given showing how functional organic moieties, such as polymerizable groups, can be incorporated into sol-gel materials via the complexing ligands. Major structural differences between silica-based and metal-based hybrid materials originate from the different charge/coordination number ratios of silicon and most metals. This results in a high tendency for the molecular building blocks to aggregate. In many cases, metal oxide clusters are formed which are capped by the organic ligands. Such surface-modified clusters are themselves very valuable condensed matter units for materials syntheses.     

铂锡双金属催化剂上丙烷脱氢反应研究

对比研究了Ｓｎ／Ｐｔ比为１；１，２，：１和５：１的原子簇担载于γ－Ａｌ２Ｏ３上制成的Ｐｔ＝Ｓｎ原子簇催化剂，和用ＳｎＣｌ２和Ｈ２ＰｔＣｌ６浸渍制备的相应Ｓｎ／Ｐｔ比的催化剂对丙烷脱氢生成丙烯的催化性能。     

超声波作用下羰基化合物的还原偶联反应

超声波在一些有机反应中有明显的促进作用「“，Luche等认为超声波的作用有两种主要类型［’j．一类是涉及电子转移的自由基或离子一自由基型反应，由于超声波的空化作用所产生的局部高温高压可以促进电子转移，从而明显地加快反应速度；对大多数离子型反应，超声波只能起到机械的物理作用．我们曾报道偕二卤化合物在Li、Na、Mg等金属作用下产生卡宾的反应是单电子转移过程，该反应可由于超声辐射而大大加速［‘］；而在芳基叔脚的断裂反应中，超声波可以促进三苯基俄与金属馊反应生成二苯基脚负离子，但对它进一步的亲核取代反应却没有明…     

Carbon dioxide reduction under visible light: a comparison of cadmium sulfide and titania photocatalysts

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Pt羰基簇合物在NaY内的合成机理

利用IR，EXAFS, ~(13)CO同位素交换反应及与NO作用等手段研究了Pt羰基簇合物[Pt_3(CO)_6]~(2-)_n(n＝3,4)在NaY分子筛超笼内的合成机理．在氧化样品Pt~(2+)/NaY上300－373 K的还愿羰基化过程中，首先Pt~(2+)与CO反应生成PtO(CO)物种(波数σ_(CO)＝2110 cm~(-1))，然后聚集成“Pt_3(CO)_6”(σ_(CO)＝2112，1896和1841 cm~(-1))，最后生成深绿色的Pt羰基簇合物Pt_(12)(CO)_(24)]~(2-)/NaY(σ_(CO)＝2080，1824 cm~(-1))．“Pt_3(CO)_6”的羰基在室温下能迅速地与~(13)CO发生交换，而[Pt_3(CO)_6]~(2-)_n(n＝3,4)的羰基与~(13)CO的同位素交换即使在343 K也进行得很慢，室温下，NO能逐步破坏Pt羰基簇合物的层间和层内Pt－Pt键，得到中间物种“Pt_3(CO)_6”和PtO(CO)，同时在气相产生CO_2和N_2O．而由上述两中间物种出发，300－353 K温度下，在CO气氛中的还原羰基化又能可逆地得到原羰基簇合物．     

Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process

Metal foams, now one of research foci, are a newclass of materials with low densities and novel physi-cal, mechanical, thermal, electrical and acoustic prop-erties[1—8]. Demands from high-tech make Al alloyfoam, which has much higher specific strength than ofpure Al foam, the new development focus[9—11]. Melt foaming process is one of the approaches tofabricate Al foam and Al alloy foam and their porestructure (pore diameter and porosity) has close rela-tionship with the thermal decompo…     

<Emphasis Type="Italic">Ab initio</Emphasis> study of small coinage metal telluride clusters Au<Subscript>n</Subscript>Te<Subscript>m</Subscript> (<Emphasis Type="Italic">n,m</Emphasis> = 1, 2)

The geometries of the most stable isomers of gold telluride systems AuTe, Au₂Te, and AuTe₂ are determined using the MP2 method. The aspect of gold—telluride interaction, the electron correlation, and relativistic effects on geometry and stability are investigated at the MP2 and CCSD(T) theoretical levels. The results show that the electron correlation and relativistic effects are responsible not only for gold—gold attraction but also for additional gold—telluride interaction. The gold—telluride interaction is strong enough to modify the known pattern of bare gold clusters. Both effects are essential for determining the geometry and relative stability of this type of systems.     

Mesoporous titanium dioxide as a novel solid-phase extraction material for flow injection micro-column preconcentration on-line coupled with ICP-OES determination of trace metals in environmental samples

Mesoporous titanium dioxide as a novel solid-phase extraction material for flow injection micro-column preconcentration on-line coupled with ICP-OES determination of trace metals (Co, Cd, Cr, Cu, Mn, Ni, V, Ce, Dy, Eu, La and Yb) in environmental samples was described. Possessing a high adsorption capacity towards the metal ions, mesoporous titanium dioxide has found to be of great potential as an adsorbent for the preconcentration of trace metal ions in samples with complicated matrix. The experimental parameters including pH, sample flow rate, volume, elution and interfering ions on the recovery of the target analytes were investigated, and the optimal experimental conditions were established. Under the optimized operating conditions, a preconcentration time of 90 s and elution time of 18 s with enrichment factor of 10 and sampling frequency of 20 h⁻¹ were obtained. The detection limits of this method for the target elements were between 0.03 and 0.36 μg L⁻¹, and the relative standard deviations (R.S.D.s) were found to be less than 6.0% (n =7, c =5 ng mL⁻¹). The proposed method was validated using a certified reference material, and has been successfully applied for the determination of the afore mentioned trace metals in natural water samples and coal fly ash with satisfactory results.     

Theoretical study on the adsorption of aromatic compounds on platinum clusters

B3 LYP hybrid functional with LACVP* pseudopotential was applied for the optimization of geometries of complexes resulting from interaction of benzene, pyridine, naphthalene, and quinoline with Pt_n (n = 4, 7) clusters. For benzene‐containing complexes, the most stable form corresponds to a bridge adsorption, with benzene undergoing considerable geometric distortions, assuming a boat‐like conformation. C? H bonds are bended upward from the plane of the cluster. C? C bonds stretch, especially when they form π‐complexes with low coordinated Pt atoms. Some arrangements for pyridine complexes involving the N atom of the organic moiety undergo further distortions, apparently preserving a formal C? N π bond. Except for that distortion, the behavior of any heteroaromatic complex is similar to that of benzene in the same arrangement. The quinoline–Pt₇ complex can suitably be used for simulation of the cinchonidine (CD) anchorage over Pt. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003