表面金属有机化学:SnMe4在HY沸石超笼表面的接枝反应

研究了高真空条件下SnMe4在HY沸石超笼的接枝反应,并用元素分析,ICP, GC, XRD, FTIR, DTG, DTA, UV-vis, DRS, N2吸附等方法对产物的组成、结构和性质进行了详细表征.研究结果表明,两者可以定量地、有选择性地进行化学反应,将确定数目的三甲基锡基团接枝在沸石的超笼中.反应可以在非常低的温度下快速进行,表观活化能为10.4 kJ·mol-1.经SnMe4改性后的HY沸石分子筛BET比表面积降低,孔体积变小,对不同尺寸的烃分子表现出明显的吸附择形性.     

Adsorption of Ethyl(hydroxyethyl)cellulose onto Silica Particles: The Role of Surface Chemistry and Temperature

The adsorption characteristics of an ethyl(hydroxyethyl)cellulose (EHEC) polymer onto colloidal silica particles from aqueous solution have been investigated. The influence of solution temperature and the silica surface chemistry on EHEC adsorption isotherms and adsorbed layer thicknesses have been determined in an attempt to elucidate the mechanisms of adsorption. As the hydrophobicity of the silica particles are increased by physical and chemical treatment, the plateau EHEC adsorbed amount increased, while the corresponding adsorbed layer thickness decreased. The estimated free energy of adsorption (DeltaG(o)(ads)) was shown to be dependent on the silica surface chemistry, but did not correlate directly with silica's advancing water contact angle and suggests that EHEC adsorption is not directly controlled by hydrophobicity alone. As the solution temperature increased from 18 to 37 degrees C, the plateau coverage of EHEC increased while the layer thickness generally decreased, this concurred with a reduction in the solvency. For hydrophilic and dehydrated silica particles, DeltaG(o)(ads) decreased in magnitude with increasing temperature, whereas for chemically treated silica, DeltaG(o)(ads) increased with temperature. These findings are discussed with respect to the specific interactions between EHEC segments and surface sites, which control the adsorption mechanisms of cellulose polymers. Copyright 2000 Academic Press.     

Molecular Organometallic Chemistry on Surfaces: Reactivity of Metal Carbonyls on Metal Oxides

Metal carbonyls react on metal oxide surfaces to give a wide range of structures analogous to those of known compounds. The reactions leading to formation of surface-bound metal carbonyls are explained by known molecular organometallic chemistry and the functional group chemistry of the surfaces. The reaction classes include formation of acid-base adducts as the oxygen of a carbonyl group donates an electron pair to a Lewis acidic center; nucleophilic attack at CO ligands by basic surface hydroxyl groups or O^2? ions; ion-pair formation by deprotonation of hydrido carbonyls to give carbonylate ions; interaction of bifunctional complexes with surface acid-base pair sites such as [Mg^2⊕O^2?]; and oxidative addition of surface hydroxyl groups to metal clusters. The reactions of surface-bound organometallic species include redox condensation and cluster formation on basic surfaces (paralleling the reactions in basic solution) as well as oxidation of mononuclear metal complexes and oxidative fragmentation of metal clusters by reaction with surface hydroxyl groups. Most supported metal carbonyls are unstable at high temperatures, but some, including osmium carbonyl cluster anions on the basic MgO surface, are strongly stabilized in the presence of CO and are precursors of catalysts for CO hydrogenation at 550 K.     

离子型表面活性剂自组装体系在化学中的应用

本文介绍了离子型表面活性剂在氧化物表面自组装体系的原理及特点,离子型表面活性剂分子从溶液中自发地吸附到氧化物表面形成单分子胶束、双分子胶束和混合胶束,该体系对许多疏水性有机化合物以及经螯合有机基团的金属离子具有很强的吸附富集作用,本文根据不同自组装体系的结构分类详述了它们在分析化学和环境化学中应用研究,并且展望了该技术的应用前景。     

Synthesis of Poly(methyl acrylate) Grafted onto Silica Particles by Z-supported RAFT Polymerization

RAFT polymerization of methyl acrylate (MA) mediated by silica-supported 3-(methoxycarbonyl-phenyl-methylsulfanylthiocarbonylsulfanyl) propionic acid (Si- MPPA) and 3-(benzylsulfanylthiocarbonylsulfanyl) propionic acid (Si-BSPA) was investigated. The molecular weight and polydispersity of grafted polymeric chains and the grafted chain transfer agent (CTA) efficiency (G_e) were strongly dependent on the types and loading of Si-CTAs and free CTA used in solution. Under similar reaction conditions, the graft polymerization mediated by Si-MPPA was better controlled than that using Si-BSPA. The introduction of a free CTA in solution during Si-MPPA mediated polymerization could significantly decrease the polydispersity of free and grafted polymeric chains and enhance the grafted CTA efficiency, and longer polymeric chains could be grafted onto silica support when Si-MPPA with a higher CTA loading was used to mediate the polymerization. In all cases, the RAFT polymerization using 2-(2-cyanopropyl) dithiobenzoate (CPDB) as a free CTA could afford well-defined grafted PMA and significantly increased G_e value, while the polymerization rate was also decreased.     

Bis(allyl)zinc revisited: sigma versus pi bonding of allyl coordination

The reinvestigation of two allyl zinc compounds, parent bis(allyl)zinc [Zn(C(3)H(5))(2)] (1) and 2-methallyl chloro zinc [Zn(C(4)H(7))Cl] (2), revealed two new coordination modes in the solid state for the allyl ligand, viz cis- and trans-μ(2)-η(1):η(1). These results call for modification of the conventional interpretation of zinc-allyl interactions. Computational results indicate that the classical η(3)-bonding mode of the allyl ligand is not favored in zinc compounds. A rare case of a zinc-olefin interaction in the dimer of [Zn(η(1)-C(3)H(5))(OC(C(3)H(5))Ph(2))] was found in the monoinsertion product of 1 with benzophenone.     

Unprecedented Bifunctional Chemistry of Bis(acyl)phosphane Oxides in Aqueous and Alcoholic Media

Tailor-made photoinitiators play an important role for efficient radical polymerisations in aqueous media, especially in hydrogel manufacturing. Bis(acyl)phosphane oxides (BAPOs) are among the most active initiators. Herein, we show that they display a remarkable photochemistry in aqueous and alcoholic media: Photolysis of BAPOs in the presence of water or alcohols provides a new delocalized π-radical, which does not participate in the polymerization. It either converts into a monoacylphosphane oxide acting as a secondary photoactive species or it works as a one-electron reducing agent. Upon the electron-transfer process, it again produces a dormant photoinitiator. We have established the structure and the chemistry of this π radical using steady-state and time-resolved (CIDEP) EPR together with ESI-MS, NMR spectroscopy, and DFT calculations. Our results show that bis(acyl)phosphane oxides act as bifunctional reagents when applied in aqueous and alcoholic media.     

Bis(allyl)gallium cation, tris(allyl)gallium, and tetrakis(allyl)gallate: synthesis, characterization, and reactivity

A series of cationic, neutral, and anionic allylgallium complexes has been isolated and fully characterized. It includes neutral [Ga(η(1)-C(3)H(5))(3)(L)] (1, L = THF; 2, L = OPPh(3)), cationic [Ga(η(1)-C(3)H(5))(2)(THF)(2)](+)[A](-) (3, [A](-) = [B(C(6)F(5))(4)](-); 4, [A](-) = [B(C(6)H(3)Cl(2))(4)](-)), as well as anionic [Cat](+)[Ga(η(1)-C(3)H(5))(4)](-) (5, [Cat](+) = K(+); 6, [Cat](+) = [K(dibenzo-18-c-6](+); 7, [Cat](+) = [PPh(4)](+)). Binding modes of the allyl ligand in solution and in the solid state have been studied comparatively. Single crystal X-ray analyses revealed a four-coordinate neutral gallium center in 2, a five-coordinate cationic gallium center in 4 and [4·THF], and a four-coordinate anionic gallium center with a bridging μ(2)-η(1):η(2) coordination mode of the allyl ligand in 6. The reactivity of this series of allylgallium complexes toward benzophenone and N-heteroaromatics has been investigated. Counterion effects have also been studied. Reactions of 1 and 5 with isoquinoline revealed the first examples of organogallium complexes reacting under 1,2-insertion with pyridine derivatives.     

基于表面金属有机化学方法的硅胶表面氧化钛的制备及表征

以普通硅胶为载体, 采用表面金属有机化学合成技术, 通过“一锅”反应制备了硅胶表面金属有机钛化合物, 然后经高温煅烧获得了硅胶表面氧化钛. 采用傅里叶变换红外光谱(FTIR)、 X射线光电子能谱(XPS)、 热重分析(TG-DTA)及原子力显微镜(AFM)对硅胶表面金属有机钛化合物和表面氧化钛进行了结构表征. 结果表明, 高温煅烧过程中, 硅胶表面金属有机钛化合物不仅脱除了有机配体, 并且通氧使其表面“再生”羟基, 确保了钛的四配位形式不变; 氧化钛通过Si—O—Ti键锚定在硅胶表面, 呈分散、 孤立状态分布. 高温煅烧后, 硅胶的骨架结构保持完好.     

Reaction of Triphenylbismuth Bis(arenesulfonates) with Triphenylstibine

Tetraphenylantimony arenesulfonates and diphenylbismuth arenesulfonates were prepared by reaction of triphenylbismuth bis(arenesulfonates) with triphenylstibine in toluene at 25°C. The crystal and molecular structure of diphenylbismuth 2,4-dimethylbenzenesulfonate was studied by single crystal X-ray diffraction. The molecules of the compound in the crystal form chains of Ph₂BiOSO₂C₆H₃Me₂-2,4 fragments linked with oxygen atoms of the sulfo group of the bridging arenesulfonate ligand.     

Reaction of Palladium Bis(Acetylacetonate) with Phenylphosphine

The reaction between palladium bis(acetylacetonate) and phenylphosphine was performed at different ratios of reagents and studied by the spectral and X-ray powder diffraction methods. It was shown that the reaction of PH₂Ph with Pd(Acac)₂ does not terminate in complexation but is accompanied by the exchange of acido ligands for organophosphorus ligands and the formation of associates of palladium complexes containing the bridging ³-PPh, ²-PHPh, O,O-chelate Acac ligands and the coordinated phenylphosphine molecules. When the reagent ratio is increased to PH₂Ph : Pd(Acac)₂ > 2, Acac^- is fully replaced by organophosphorus ligands.     

Adsorption-desorption of Silica Nanoparticles on Poly(ethylene glycol) Brushes Grafted onto Au Substrate Studied by Quartz Crystal Microbalance

The adsorption-desorption of silica nanoparticles(NPs) on poly(ethylene glycol)(PEG) grafted onto gold(Au) substrate was studied by quartz crystal microbalance with dissipation monitoring(QCM-D) technique. The results of frequency and dissipation show that SiO₂ NPs can be adsorbed strongly on PEG-SH brushes at pH of 9.6, and a new dense and rigid construction is formed. Adjusting the pH from 9.6 to 12.3 resulted in the desorption of silica NPs from the PEG brushes because of a significant weakening of the hydrogen bond between the silica NPs and PEG chains. In addition, the viscoelastic properties of the system during the adsorption-desorption process were also analyzed via the relationship between the normalized frequency(Δf/n) and mass. And the corresponding atomic force microscopy(AFM) images also exhibit morphological changes during the above process, consistent with the changes in viscoelasticity.     

Reaction of Palladium Bis(acetylacetonate) with Diphenylphosphine: Spectral Studies

Interaction of palladium bis(acetylacetonate) with diphenylphosphine is studied by NMR, IR, and UV methods. Reaction between reagents taken in equimolar amounts gives binuclear and trinuclear palladium complexes with bridging diphenylphosphide and the chelate acetylacetonate [Pd(Acac)PPh₂]₂ and [Pd₃(Acac)₂(PPh₂)₄] ligands. With excess PPh₂H, the trinuclear palladium complex, whose composition is supposed to be [Pd₃(PPh₂)₄(PPh₂–PPh₂) · C₆H₆], is isolated and characterized on the basis of the spectral data.     

Addition Reaction of Bis（diphenylphosphinyl） Butadiyne with Methylcyclopentadiene

Bis(diphenylphosphinyl)butadiyne reacted with methylcyclopentadiene at room tem- perature and four isomeric products were obtained. Crystal structures of isomers 1 and 3 have been determined. Crystal data for compound 1 C40H36O2P2·2CHCl3: monoclinic, space group C12/c1 with a = 17.983(2), b = 11.8723(12), c = 20.081(2) , β = 111.218(3)°, V = 3996.5(8) 3, Z = 4, Mr = 849.36, Dc = 1.412 g/cm3, F(000) = 1752, μ = 0.546 mm-1, the final R = 0.0351 and wR = 0.0951 for 3965 observed reflections (I > 2σ(I)); and those for compound 3 C40H36O2P2·H2O: triclinic, space group P1 with a = 10.4144(15), b = 13.0558(18), c = 13.742(2) , α = 70.453(8), β = 75.382(8), γ = 72.312(8)°, V = 1653.7(4) 3, Z = 2, Mr = 628.64, Dc = 1.262 g/cm3, F(000) = 664, μ = 0.169 mm-1, the final R = 0.0593 and wR = 0.1296 for 4891 observed reflections (I > 2σ(I)). The structures of the other two isomers are identified via IR, 1H NMR and MS spectra.     

Reaction of Bis(trimethylsiloxy)phosphine with Methyl(phenyl)divinylsilane

Russian Journal of General Chemistry -     

Molecular Orbital Calculation and Spectroscopic Study of the Photochemical Generation of Bis(2,2'-bipyridine)rhodium(I) from Bis(2,2'-bipyridine)(oxalato)rhodium(III)

A planar complex, [Rh(bpy)(2)](+) (bpy = 2,2'-bipyridine), was obtained from [Rh(ox)(bpy)(2)](+) (ox = oxalato) by photoirradiation. A rate constant k for the photoreaction was evaluated as 1 x 10(8) s(-1) in simple first-order kinetics, whereas a ligand dissociation, a reorganization of the coordinated bpy, and a two-electron transfer were involved in the reaction. The process of the Rh(I) complex generation was investigated in terms of a discrete variational (DV)-Xalpha molecular orbital calculation on [Rh(ox)(HN=CHCH=NH)(2)](+) instead of [Rh(ox)(bpy)(2)](+). From the calculation, using the transition-state method, it was predicted that a transition of the ox pi orbital to the metal 4d(z)()2 orbital caused the ligand dissociation and the reorganization of the coordinated bpy occurred in the ox pi to Rh 4d(x)()2(-y)2 excited state stabilized by the ox elimination. Upon release of the ligand and a change from octahedral to square-planar geometry, the electron density on the metal increased and the Rh 4d orbital acquired a d(8) electronic configuration.