Bildung und Kristallstruktur eines dimeren sauerstoffverbrückten Titanaminobisphenoxides

Formation and Crystal Structure of an Oxygen Bridged Titanium Amino Bisphenoxide Di‐(μ‐oxo)‐titan‐bis[aminobisphenoxide] ( 3 ) was obtained by reaction of (i‐Prop)₂TiL* ( 2 ) {L* = O‐4, 6‐(t‐Bu)₂C₆H₂‐2‐CH₂‐[1, 4‐N₂C₅H₁₀]‐2'‐CH₂‐4', 6'‐(t‐Bu)₂C₆H₂O] with water in a molar ratio 1:1 in diethylether. Both i‐Propyl moieties are substituted yielding the dimeric oxygen bridged amino bisphenoxide complex. The six coordinate Ti atoms are a result of Ti—N and Ti—O interactions of the corresponding atoms of the amino bisphenoxide ligand and the bridging O atoms. The central planar Ti₂O₂ ring may be considered as the general structural feature of the title compound: Space group P1¯, Z = 1, lattice dimensions at —60°C: a = 11.6899(4), b = 11.7873(4), c = 12.6462(4) Å, α = 98.070(1), β = 99.660(1), γ = 95.343(1)°, R₁ = 0.0469, wR₂ = 0.1049, GooF = 0.939.     

Mesoporous electrode material from alumina-stabilized anatase TiO2 for lithium ion batteries

A mesoporous electrode material whose structure is composed of anatase nanocrystals stabilized by alumina is reported. Powder X-ray diffraction shows the anatase phase only, but micro-Raman spectroscopy shows that the materials have a core-shell morphology with grains of bulk anatase covered by a thin rutile layer on the surface. This structure is unique when compared to analogous materials stabilized by zirconia (PNNL-1). Nitrogen adsorption isotherms demonstrate a monotonous increase in surface area and mesopore volume with increasing Al content. Thin film electrodes from these materials were characterized by lithium insertion electrochemistry. Cyclic voltammograms exhibit significant differences in Li accommodation in Al-free and Al-stabilized materials.     

SO_4~(2-)/TiO_2固体超强酸新制备方法及其对形成邻苯二甲酸二丁酯的催化活性

建立了用钛白粉制备固体超强酸SO42-/TiO2的新方法.考察了超强酸SO42-/TiO2的制备条件对催化邻苯二甲酸酐和正丁醇酯化反应的催化活性的影响.实验表明,以合成的超强酸为催化剂,在160℃反应4h,邻苯二甲酸二丁酯的产率大于99%.     

钇对IMI829钛合金及Ti—14Al—21Nb合金显微组织和性能的影响

采用光学显微镜、扫描电和力学性能测试设备，研究了在ＩＭＩ８２９和Ｔｉ－１４Ａｌ－２１Ｎｂ合金中添加Ｙ，对合金显微组织遥影响。结果表明，在ＩＭＩ８２９和Ｔｉ－１４Ａｌ－２１Ｎｂ合金中添加Ｙ，可以细化这两种合金的组织和晶粒，使ＩＭＩ８２９－０．２Ｙ合金获得良好的室温力学性能和５５０℃蠕变性能，ｗｇｋｑＴｉ－１４Ａｌ－２１Ｎｂ－０．１Ｙ合金的高温力学性能得到改善。     

The synthesis and electrochemistry of CpTiCl2(OR) (R = alkyl, aryl) complexes

The syntheses of several new CpTiCl₂(OR) (R = alkyl, aryl) complexes are described. It was possible to isolate pure product when the R group is substituted such as to cause steric crowding at the metal centre; for example, particularly good yields of the phenolate complexes were obtained when there were isopropyl substituents in the 2 and 6 positions of the phenolate. Electrochemical studies of the complexes in dry THF show that the Ti^III complexes are relatively stable, but only a diol complex could be reduced further to a Ti^II species. In general, the Ti^IV complexes undergo a reversible 1e⁻ reduction reaction. The chemistry is more complex if the electrolyte contains added water: both the Ti^IV and Ti^III complexes can react with water, the OR group being replaced by OH. The reaction is particularly rapid for the Ti^III alkoxide complexes.     

钇对Ti-1100高温钛合金热稳定性和蠕变行为的影响

量了Ｔｉ１１００和Ｔｉ１１００／０１％Ｙ（质量分数）高温钛合金在６００℃／１００ｈ空气中暴露后的拉伸性能及在６００℃／１５０ＭＰａ／１００ｈ条件下的蠕变性能，利用透射电镜观察了合金室温及蠕变后的组织。结果表明，Ｔｉ１１００合金加入０１％的Ｙ后，由于原始β晶粒得到细化，明显改善了其热稳定性；固溶在基体中的硅原子阻碍位错滑移和攀移，使蠕变中的回复过程难于实现；稀土还抑制α２相的长大，所形成的氧化物也阻碍位错的运动。这些均有利于提高Ｔｉ１１００合金的抗蠕变性能。     

钛硅分子筛TS-1合成晶化气氛的影响

考察了不同晶化气氛(N2、H2、A ir、O2)对合成钛硅分子筛TS-1的影响,用XRD、IR和N2吸附/脱附对所合成的钛硅分子筛进行结构表征,发现在H2气氛下合成的TS-1结晶度最高,锐钛矿的含量最少;O2气氛下合成的TS-1中锐钛矿含量最高.以氯丙烯氧化为模型反应,考察了不同晶化气氛下合成的钛硅分子筛的催化活性和双氧水的利用效率.结果表明,在H2气氛下所合成的钛硅分子筛的双氧水的利用效率最高.     

负载贵金属光催化剂的光催化活性研究

在注入V离子的二氧化钛光催化剂上负载贵金属,制备了在可见光照射下具有高光催化活性的功能型光催化剂,研究在可见光和太阳光照射下丙炔的光催化水解反应，利用这些改性的二氧化钛构筑太阳能到化学能的转换系统.研究结果发现了V/Pt光催化剂在丙炔和水的光催化水解反应中，由于贵金属的存在，有利于促进发生加氢反应；导致丙烯的生成量增加.在可见光下的光催化活性也和负载贵金属所处的氧化状态有着密切的关系，贵金属完全被还原到0价是提高光催化活性的必要条件.     

Carbenoid Complexes of Electron-Deficient Transition Metals—Syntheses of and with Short-Lived Building Blocks

The relation of thermodynamic stability and kinetic lability of σ-organometallic compounds of transition metals, together with an improved understanding of the subtle interactions between central metal, ligands, and substrates, has increased the chemist's ability to plan organometallic syntheses. This article presents new results on intermediary and isolable synthetic building blocks incorporating metal–ligand multiple bonds of electron-deficient transition metals; the main emphasis will be placed on compounds with titanium–carbon double bonds. This particular class of compounds is mainly generated by H-transfer reactions starting from readily accessible alkyl and alkenyl derivatives. The preparative use of [L₂Ti(CHR₂)R′] derivatives as sources for [L₂Ti?CR₂] intermediates will be discussed, as well as the nature of these intermediates. Application of the same approach to vinyltitanium compounds [L₂Ti(CH?CH₂)R] opens up an access to a short-lived metallaallene derivative [L₂Ti?C?CH₂] of an electron-deficient transition metal. The reactivity of these synthetic building blocks is mainly characterized by the nucleophilic properties of the α-C atoms as well as by the spatial orientation of the π-bonding planes. Numerous cycloaddition products with unsaturated substrates could be isolated and characterized for the first time by using [L₂Ti?C?CH₂] intermediates. Hence it is possible to compare the properties of a multitude of metallacyclic ring systems with those obtained from “Tebbe–Grubbs chemistry”, and in this context, the dependence of the properties of metallacyclic four-membered rings on the substitution pattern is discussed. This class of compounds includes the metallaoxetanes, which have been obtained for the first time by the cycloaddition of the [CpTi?C?CH₂] intermediate with cumulenes and metal carbonyls. The differing cycloreversion behavior of these metallaoxetanes enables the differentiation of species exhibiting classical and nonclassical reactivity. The number and position of the exocyclic double bonds are the determining factors of the reactivity of the formed metallacycles. The discussion of the products obtained from titanium methylene and vinylidene building blocks is an up-to-date report on the formation and applications of carbene complexes and carbene intermediates of group 4 metals.     

An NMR study of the species produced by the reactions of dialkyl magnesium and HCl with calcined silica and the polymerisation performance of Ziegler-Natta catalysts produced from this support material

The effect of calcinations on the silica surface groups and thereby on the activity of Ziegler-Natta catalysts in ethylene homopolymerisation has been studied. Silica was calcined at different temperatures and treated with MgR₂ and HCl. Silica surface groups were identified by using ¹H MAS NMR and ¹³C and ²⁹Si CP MAS NMR techniques. Magnesium, titanium and chlorine were measured by elemental analysis. Ziegler-Natta catalysts were prepared from these supports and subsequently used in ethylene homopolymerisation. Maximum activity was obtained with the catalyst based on 590 °C calcined silica. The results indicate that MgR₂ reacts with siloxane-groups (Si-O-Si) in the 300 °C calcined silica, leaving the hydrogen-bonded hydroxyl-groups unreacted. Low activity Si-O-Ti(Cl)₂-O-Si species are formed after reacting with TiCl₄. The higher activity in the catalyst based on 590 °C calcined silica can be explained by the formation of -Si(R)-O-Si-O-TiCl₃ groups, originating from the siloxane bridges which cannot form in 300 °C calcined silica. Other explanations for the higher activity are a higher Mg/Ti ratio or small amounts of crystal water formed in the 590 °C calcined silica.