catena‐Poly[tris(μ3‐acetylacetonato)nickelate(II)sodium(I)]

The title complex, [NaNi(C₅H₇O₂)₃]_n, contains an anionic tris(acetylacetonato)nickelate(II) unit, [Ni(acac)₃]⁻ (acac is acetylacetonate), with a highly regular octahedral coordination geometry. The Ni^II cation lies on a Wyckoff a site, resulting in D₃ symmetry of the anion. Charge balance is provided by sodium cations, which occupy Wyckoff type b sites. Each sodium cation is surrounded by two [Ni(acac)₃]⁻ anions, each of which is connected to the alkali metal through three O atoms, in a fac configuration. This arrangement leads to the formation of linear [Na{Ni(acac)₃}]_n chains along the c axis. The Ni...Na distance is 2.9211 (10) Å. The title complex is one of the few examples of heterometallic systems based on alkali and transition metal cations bridged by acetylacetonate ligands.     

Oxidative thermolysis of Mn(acac)3 on the surface of γ-alumina support

Precipitated γ-alumina support was decorated with Mn(acac)₃ by incipient wetness impregnation with toluene solutions containing Mn(acac)₃ in amount equivalent to loading of 0.35, 0.74, 1.38, 2.38 and 3.50 Mn(acac)₃ moleculs per nm² of the support. In order to evaluate the mechanism of Mn(acac)₃ interaction with the surface of γ-alumina support and subsequent transformations of the supported Mn(acac)₃ species, oxidative thermolysis of Mn(acac)₃/Al₂O₃ samples in air was studied by diffuse reflectance FTIR, thermogravimetric analysis (TG/DTG), differential thermal analysis (DTA) and XRD. It has been found out that decoration of γ-Al₂O₃ support with Mn(acac)₃ results in the formation of surface bound Mn(acac)_3−x species when Mn(acac)₃ loading does not exceed 1.38 Mn(acac)₃/nm². At higher Mn(acac)₃ loading the formation of the supported bulk-like Mn(acac)₃ species also occurs. The interaction of Mn(acac)₃ molecules with the support surface occurs via substitution of acetylacetonate ligand(s) with the oxygen atom of surface hydroxyl group(s) accompanied by elimination of acetylacetone molecules. The evolved acetylacetone reacts with the alumina surface that results in the formation of surface Al(acac)_3−x species. The oxidative thermolysis of Mn(acac)_3−x species on the surface of γ-alumina proceeds via partial elimination of acetylacetonate ligands and partial oxidation of the remaining ligands without destruction of their cyclic structure within 425-550 K. The complete oxidative destruction of acetylacetonate ligands takes place within 600-700 K and results in the formation of manganese oxide species on the alumina surface. The dispersed surface manganese oxide species originate upon the oxidative thermolysis of the surface bound Mn(acac)_3−x species while crystalline Mn₂O₃ phase results from the supported bulk-like Mn(acac)₃ species.     

Color tunable phosphorescent light-emitting diodes based on iridium complexes with substituted 2-phenylbenzothiozoles as the cyclometalated ligands

Several iridium complexes {iridium(III)bis[2-(3-methoxyphenyl)-1,3-benzothiozolato-N,C^2′] acetylacetonate (MeO-BT)₂Ir(acac), iridium(III)bis[2-(2,4-difluorophenyl)-1,3-benzothiozolato-N,C^2′] acetylacetonate (2F-BT)₂Ir(acac), and iridium(III)bis[2-(2,4-difluorophenyl)-6-fluoro-1,3-benzothiozolato-N,C^2′] acetylacetonate (3F-BT)₂Ir(acac)} having different substituents on 2-phenylbenzothiazole have been synthesized. The phosphorescent light emitting diodes (PHOLEDs) using these iridium complexes as dopant emitters were fabricated. The experimental results revealed that the emissive colors of PHOLEDs could be finely tuned by suitable modification of the substituents on the 2-phenylbenzothiazole ligands. Furthermore, these iridium complexes show better emissive properties than the known iridium(III)bis(2-phenylbenzothiozolato-N,C^2′) acetylacetonate (BT)₂Ir(acac).     

无定形硅铝负载镍催化剂上乙烯齐聚反应的活性位点结构鉴定

镍(Ni)基催化剂在低碳烯烃聚合领域具有重要的地位,也是该领域研究的热点.自Johnson等报道(J.Am.Chem.Soc.,1995,117,6414–6415)二亚胺配体络合的Ni(Ⅱ)催化剂可有效降低烯烃聚合度,降低产物中非线性烯烃的选择性,甚至可以生成α-烯烃以来,掀起了Ni基催化剂在烯烃聚合领域的研究热潮.从均相到负载型多相Ni基催化剂,从载体类型到配体性质,从Ni纳米粒子的粒径调控到金属表面价态,关于Ni活性中心的研究工作一直存在争论.本课题组之前研究结果表明,曾明确了无定形硅铝(ASA)载体负载的Ni催化剂,经惰性气氛(N2)预处理得到的一价Ni是烯烃齐聚反应的主要活性中心(J.Chem.Soc.Chem.Commun.,1991,126–127).本文进一步深入研究了不同Al2O3含量的ASA载体上Ni活性位点的结构及其在乙烯齐聚反应中的活性.27Al NMR结果表明,催化剂中的铝存在三种配位方式,分别为AlⅣ、AlⅤ和AlⅥ,其中AlⅣ含量随Al2O3含量的增加而增加.载体中铝配位方式的不同,导致其表面金属负载的金属Ni活性位点所处的结构亦不同.原位FTIR-CO和H2-TPR实验结果表明,催化剂表面存在两种不同结构分布的Ni位点,分别是接枝在弱酸性硅醇上的Ni2+阳离子和Si?(OH)?Al桥式羟基离子交换位置的Ni2+阳离子.多数研究者认为,位于离子交换位置处孤立的Ni阳离子是反应的活性中心.然而,近期有研究者提出负载在酸性硅烷醇表面孤立的Ni2+阳离子为反应的活性中心物质.本文研究发现,随着Al2O3负载量的降低,处于离子交换位置处的Ni2+离子含量逐渐减少,而处于硅醇缺陷位点处的Ni2+离子含量则逐渐增多.原位FTIR-CO分析结果表明,处于硅醇缺陷位点处的Ni2+离子物种在惰性气氛中更易于转化为活性中心Ni+.相应的催化反应结果表明,相比于离子交换位置的Ni2+物种,具有与硅醇缺陷位点相连的Ni2+离子结构更有利于表现出更高的乙烯齐聚化活性.由此可知,处于硅醇缺陷位点的Ni2+物种是乙烯齐聚反应的活性中心的前驱体.本文进一步研究了硅醇缺陷位点处的Ni2+离子物种更易于转化为活性中心Ni+的原因.H2-TPR结果表明,相比于离子交换位置的Ni2+物种,处于硅醇缺陷位点的Ni2+物种与载体之间的相互作用力更弱.C2H4-TPD结果进一步表明,具有这种相对较弱的金属载体间作用力结构的催化剂对反应物C2H4分子的吸附作用力相对更强,吸附量也相对增多,因此其乙烯齐聚的催化性能更优.本研究结果对理解活性中心结构和合理设计催化剂提供参考.     

Untersuchungen an Nickeloxid-Mischkatalysatoren. XI. Oberflächenchemische Eigenschaften von NiO/SiO2-Katalysatoren

Studies on Nickel Oxide Mixed Catalysts. XI. Surface Chemical Properties of NiO/SiO₂ Catalysts NiO/SiO₂ catalysts with different composition prepared by precipitation have been investigated which are characterized by a nickel layersilicate-like structure. The determination of the surface chemical properties was carried out by infrared spectroscopy (before and after pyridine adsorption), ¹H-NMR-measurements, chemisorption of ammonia, and titration with n-butylamine. It has been found three kinds of hydroxid groups which are assigned to Ni? OH and Si? OH groups with respect to investigations on definite nickel layersilicates. Furthermore, coordinatively unsaturated Ni^II surface sites were indicated. The number of the OH groups as well as the centers determined by chemisorption of bases increase with increasing NiO content. The obtained results allow the conclusion that the OH groups and the coordinatively unsaturated Ni^II surface sites are weakly acid.     

V2O5/TiO2 oxidation catalysts: Effect of sodium impurities and of the precursor salt on their texture

A series of V₂O₅/TiO₂ systems was prepared from TiO₂ (Degussa, P-25) using two precursor vanadium salts, NH₄VO₃ and VO(acac)₂ (acac, acetylacetonate). For some of the samples, the surface OH population of the starting support was increased by equilibrating a dehydroxylated support with an alkaline solution (pH 8.5) containing NaCl. In some cases the presence of Na in the final materials was observed. The structure and surface properties of the solids obtained were studied with the aid of X-ray diffraction, spectrophotometry (IR and UV-Vis), and nitrogen adsorption. The results indicate that highly dispersed, amorphous V₂O₅ is formed when NH₄VO₃ is used as precursor, and from VO(acac)₂ if the starting support is Na-free. When sodium is present, formation of the Na-V compounds is observed if VO(acac)₂ is used as precursor. In the latter case, a sharp decrease in the specific surface area, probably as a consequence of an increase in the content of rutile in the support, is observed. Both samples obtained from VO(acac)₂ exhibit a microporous structure, more developed in the sample where such Na-V compounds are formed.     

The gas‐phase ligand exchange of copper and nickel acetylacetonate,hexafluoroacetylacetonate and trifluorotrimethylacetylacetonate complexes

The gas‐phase ligand‐exchange reactions between Cu(II) and Ni(II) complexes containing the acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and trifluorotrimethylacetylacetonate (tftm) ligands were investigated using a triple quadrupole mass spectrometer. The gas‐phase mixed‐ligand products of [Cu(acac)(tftm)]⁺, [Ni(acac)(tftm)]⁺, [Cu(hfac)(tftm)]⁺, and [Ni(hfac)(tftm)]⁺ were formed following the co‐sublimation of either homo‐metal or hetero‐metal precursors. The gas‐phase formation of [Cu(acac)(tftm)]⁺, [Cu(hfac)(tftm)]⁺, [Ni(acac)(tftm)]⁺, and [Ni(hfac)(tftm)]⁺ complexes is reported herein for the first time. The corresponding fragmentation patterns of these species along with those of Cu(tftm)₂ and Ni(tftm)₂ are also presented. Mass‐selected ion‐neutral reactions were investigated. Copyright © 2009 John Wiley & Sons, Ltd.     

Polymerization of styrene to isotactic polymer with MAO-Ni(acac)2. Examination of the factors that influence activity and stereospecificity

The soluble catalyst system methylaluminoxane (MAO)-Ni(acac), (acac: acetylacetonate) gives polystyrene consisting of an amorphous (aPS) and a crystalline isotactic (ips) fraction. Al(CH₃)₃, which is always present in commercial samples of MAO, decreases both polymer yield and stereospecificity. The polymer yield increases with increasing the MAO/Ni ratio but, at the same time, the iPS/aPS ratio decreases. Addition of N(C₂H₅)₃ (mole ratio N/Ni = 1) increases the proportion of the isotactic fraction, while it decreases the polymer yield. A tentative interpretation of the stereospecificity is reported.     

Fabrication of covalently functionalized mesoporous silica core–shell magnetite nanoparticles with palladium(II) acetylacetonate: application as a magnetically separable nanocatalyst for Suzuki cross‐coupling reaction of acyl halides with boronic acids

We report the preparation of supported palladium(II) acetylacetonate, Pd(acac)₂, coordinated by pendant acac groups, by reacting palladium acetate with acac‐functionalized doubly silica‐coated magnetic nanoparticles. The solid support consists of an amorphous silica‐coated (as magnetite protecting layer) magnetite core and a mesoporous silica shell. The magnetically separable palladium nanocatalyst is active for Suzuki cross‐coupling reaction of acyl halides with boronic acids. The catalyst is simply isolated from the reaction mixture that allows fast and efficient isolation of product and catalyst compared to traditional methods that generally make use of time‐ and solvent‐consuming procedures. Copyright © 2015 John Wiley & Sons, Ltd.     

Isospecific copolymerization of styrene and a styrene‐terminated polyisoprene macromonomer with the Ni(acac)2/MAO catalyst

The copolymerization of styrene (St) with a styrene‐terminated polyisoprene macromonomer (SIPM) by a nickel(II) acetylacetonate [Ni(acac)₂] catalyst in combination with methylaluminoxane (MAO) was investigated. A SIPM with a high terminal degree of functionalization and a narrow molecular weight distribution was used for the copolymerization of St. The copolymerization proceeded easily to give a high molecular weight graft copolymer. After fractionation of the resulting copolymer with methyl ethyl ketone, the insoluble part had highly isotactic polystyrene in the main chain and polyisoprene in the side chain. Lowering the MAO/Ni molar ratio and the polymerization temperature were favorable to producing isospecific active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1241–1246, 2000     

Microsolvation of the [Ni(acac)(tmen)]+ complex

Microsolvation of the [Ni(acac)(tmen)]⁺ complex by a series of aliphatic n-alcohols (Solv) has been studied in ClCH₂CH₂Cl solutions by spectrophotometry. Based on the changes in the electronic spectrum of the afore-mentioned complex, observed under the influence of any alcohol, the equilibrium constants for the formation of the [Ni(acac)(tmen)Solv]⁺ and [Ni(acac)(tmen)Solv₂]⁺ species have been computed according to the algorithm presented in this work. It was found that, in all the systems studied, the stability of five-coordinated [Ni(acac)(tmen)Solv]⁺ is higher than that of octahedral [Ni(acac)(tmen)Solv₂]⁺. The resulting values are discussed in terms of the Lewis basicity of alcohols.     

Ni-B/SiO2非晶态催化剂应用于硝基苯液相加氢制苯胺

 考察了Ni－B／SiO2非晶态催化剂在高压液相硝基苯加氢制苯胺反应中的催化活性和选择性．研究表明,该催化剂不仅具有很高的催化活性,而且对苯胺的选择性较高,优于RaneyNi以及其它Ni基催化剂．晶化导致催化剂失活．载体的存在不仅能提高催化剂的分散度,而且能对非晶态结构起稳定化作用;将催化剂保存在乙醇中可保持其活性不变．结合催化剂的表征,讨论了Ni－B／SiO2非晶态催化剂的催化性能与其结构的关系．     

Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)₂ (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.     

The Role of the Nature of Active Centers in Chemisorption of Iron Acetylacetonate on the Surface of Amorphous Aluminosilicates and Aluminum Oxide

γ-Al₂O₃ and amorphous and structured aluminosilicates were modified with iron acetylacetonate Fe(acac)₃ in a liquid medium.     

Copolymerization of styrene and butadiene with Ni(acac)2-methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with nickel(II) acetylacetonate [Ni(acac)₂]-methylaluminoxane (MAO) catalyst was investigated. Among the metal acetylacetonates [Mt(acac)_x] examined, Ni(acac)₂ showed a high activity for the copolymerization of St and Bd giving copolymers having high cis-1,4-microstructure in Bd units in the copolymer. The effect of alkylaluminum as a cocatalyst on the copolymerization of St and Bd with the Ni(acac)₂-MAO catalyst was observed, and MAO was found to be the most effective cocatalyst for the copolymerization. The monomer reactivity ratios for the copolymerization of St and Bd with the Ni(acac)₂-MAO catalyst were determined to be r_St = 0.07 and r_Bd = 3.6. Based on the obtained results, it was presumed that the random copolymers with high cis-1,4-microstructure in Bd units could be synthesized with the Ni(acac)₂-MAO catalyst without formation of each homopolymer. The polymerization mechanism with the Ni(acac)₂-MAO catalyst was also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3838–3844, 1999     

Synthesis,X-ray structural characterization and pyrolysis studies of heterobi- and heterotrimetallic molecular complexes

Heterobi- and heterotrimetallic complexes [NiTl(acac)₂(dmae)]₂(1) and [Ba(acac)(OH₂)Ni₂(acac)₄Tl(dmae)₂] (2) (acac = acetylacetonate, dmae = N, N-dimethyl aminoethanolate) have been synthesized by simple reactions of Ni(II) acetylacetonate, Tl(I) acetylacetonate and dmaeH for (1) and Ni(II) acetylacetonate, Tl(I) acetylacetonate, Ba metal and dmaeH for (2) in toluene to obtain crystalline products that were characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis of both complexes shows that they crystallize in a monoclinic crystal system with space group P2₁/c. TGA studies of the complexes indicate that complex (1) is a suitable precursor for the preparation of composite NiO/Tl₂O₃, while complex (2) yields an unstable composite NiO/Tl₂O₃/BaO which on exposure to air is converted to NiO/Tl₂O₃/BaCO₃ by the absorption of atmospheric carbon dioxide.     

CO Oxidation on Cu/MgO-SiO2 Sol-Gel Derived Catalysts

Sol-gel Cu//MgOSiO₂ catalysts were prepared gelling tetraethoxysilane (TEOS), magnesium ethoxide and copper acetylacetonate at pH 3 and pH 9. The catalysts shown specific surface areas ca. 500 m²/g and 140 m²/g for pH 9 and pH 3 preparations respectively. Si(OH) and Si(OH)₂ hydroxy groups were observed by MAS-RMN spectroscopy in both preparations. CO₂-TPD and NH₃-TPD desorption thermograms showed that acid and basic sites were formed on the catalysts surface. It has been found that the catalysts having the highest density of basic sites were the catalysts showing the highest activity for the CO oxidation. It is proposed that the catalytic activity depends of the relative Cu⁼¹/Cu⁼² stability given by the support acidity.     

Amphiphilic block copolymers directed synthesis of mesoporous nickel-based oxides with bimodal mesopores and nanocrystal-assembled walls

Mesoporous late-transition metal oxides have great potential in applications of energy,catalysis and chemical sensing due to their unique physical and chemical properties.However,their synthesis via the flexible and scalable soft-template method remain a great challenge,due to the weak organic-inorganic interaction between the frequently used surfactants(e.g.,Pluronic-type block copolymers) and metal oxide precursors,and the low crystallization temperature of metal oxides.In this study,ordered mesoporous NiO with dual mesopores,high surface area and well-interconnected crystalline porous frameworks have been successfully synthesized via the facile solvent evaporation-induced co-assembly(EICA) method,by using lab-made amphiphilic diblock copolymer polystyrene-b-poly(4-vinylpyridine)(PS-b-P4 VP) as both the structure-directing agent(the soft template) and macromolecular chelating agents for nickel species,THF as the solvent,and nickel acetylacetonate(Ni(acac)2) as inorganic precursor.Similarly,by using Ni(acac)2 and Fe(acac)3 as the binary precursors,ordered mesoporous Fedoped NiO materials can be obtained,which have bimodal mesopores of large mesopores(32.5 nm) and secondary mesopores(4.0-11.5 nm) in the nanocrystal-assembled walls,high specific surface areas(～74.8 m~2/g) and large pore value(～0.167 cm~3/g).The obtained mesoporous Fe-doped NiO based gas sensor showed superior ethanol sensing performances with good sensitivity,high selectivity and fast response-recovery dynamics.     

Color tuning of iridium complexes for organic light-emitting diodes: The electronegative effect and π-conjugation effect

Novel red phosphorescent emitter bis(4-phenylquinazolinato-N,C^2′) iridium(acetylacetonate) [(pqz)₂Ir(acac)], bis(1-(1′-naphthyl)-5-methylisoquinolinato-N,C^2′)iridium(acetylacetonate) [(1-mniq)₂Ir(acac)] and bis(1-(2′-naphthyl)-5-methylisoquinolinato-N,C^2′)iridium(acetylacetonate) [(2-mniq)₂Ir(acac)] have been synthesized and fully characterized. The electronegative effect of (pqz)₂Ir(acac) ligand shows almost the same influence as the extended π-conjugation effect of (2-mniq)₂Ir(acac). Density functional theory (DFT) was applied to calculate the Kohn-Sham orbitals of HOMOs and LUMOs in the iridium complexes to illustrate the N(1) electronegative atom effect. Finally, lowest triplet state (T₁) energies calculated by time-dependent DFT (TDDFT) were compared with the experimental electroluminescent data. The calculated data for the iridium complexes agreed fairly well with experimental data. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ₃/LiF/Al were fabricated. The device using (pqz)₂Ir(acac) as a dopant showed deep-red emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates x = 0.70, y = 0.30.     

Copolymerization of styrene and isoprene with Ni(acac)2-methylalumoxane catalyst

Copolymerization of styrene (St) and isoprene (IP) with nickel(II) acetylacetonate [Ni(acac)₂] and methylalumoxane (MAO) catalyst was investigated. It was found that the Ni(acac)₂-MAO catalyst is effective for the copolymerization of St and IP. From the copolymerization of St (M₁) and IP (M₂) and IP (M₂) with the Ni(acac)₂-methylalumoxane catalyst, the monomer-reactivity ratios were determined to be r₁ = 1,18 and r₂ = 0,88, i.e., ideal copolymerization was found to proceed to give perfectly random copolymers without formation of any homopolymer. The microstructure of IP units in the copolymers exhibits high cis-1,4 contents.