液/液两相催化新进展--温控非水液/液两相催化

温控非水液/液两相催化,是指一类由两种或多种液态有机物组成的催化反应体系,其特点是体系的相态变化可通过温度来调控,即体系在高温时相互混溶呈均相,低温不溶分成两相,催化剂和产物分别处于两相,从而为解决均相催化剂分离难的问题开拓了一个新方向,是液/液两相催化研究领域最引人注目的进展之一.首次以"温控"为主线将氟两相催化作为温控液/液两相催化的一个特定类型纳入"温控非水液/液两相催化"范畴,并与其它通过温度来调控的有机液/液两相和作者提出的温控相分离催化串在一起作一较为详细的评述.     

温控配体与液／液两相催化

 以作者近年的研究工作为主，对液／液两相催化研究领域取得的进展做一综述．着重介绍了以温控配体为基础的新型液／液两相催化过程温控相转移催化（thermoregulatedphasetransfercatalysis，TRPTC）和温控相分离催化（thermoregulatedphase－separablecatalysis，TPSC）的基本原理及其在高碳烯烃氢甲酰化、芳香硝基化合物的CO选择性还原及烯烃加氢等反应中的应用．基于温控配体在水中的“浊点”特性而提出的温控相转移催化概念，为从根本上解决水／有机两相催化 的适用范围受底物水溶性限制的问题提供了一条新途径．而利用温控配体在某些有机溶剂中存在临界溶解温度（CST）的特性而实现的温控相分离催化，则使在高于临界溶解温度的反应温度时为均相的反应体系，在低温（＜CST）时则分成两相，催化剂自成一相，形成一种具有“均相反应、两相分离”特色的液／液两相催化新体系．     

温控液/液两相催化进展*

本文以作者在温控水/有机两相及温控非水液/液两相催化领域的研究工作为主线,对这一领域的研究进展作一评述,重点是环绕经典水/有机两相催化体系存在“应用范围受底物水溶性限制”的根本问题展开。特别是对“温控相转移催化”作了较为详细的介绍,同时,按体系介质不同,对氟两相体系、PEG两相体系、离子液体两相体系等非水液/液两相体系以及温控相分离催化分别作了阐述。     

高碳烯烃氢甲酰化研究

高碳烯烃氢甲酰化是最重要的石化技术之一.本文从均相催化体系和两相催化体系两个方面介绍了国内外近年来在研究与开发上取得的进展.两 相催化体系的开发正在成为研究的主流引人瞩目,预期新催化剂体系和两相体系在高碳烯烃氢甲酰化应用上将有突破.     

两相催化体系中长链烯烃氢甲酰化反应研究进展

水溶性有机金属络合物为催化剂的两相催化体系,由于反应条件缓和,产物和催化剂分离简便等特点,已成为发展环境友好的绿色化学的重要方向。本文介绍了近年来两相催化体系中长链烯烃氢甲酰化反应和催化剂研究进展。     

水/有机两相体系中催化氧化反应的研究进展

论述了水／有机两相体系中催化氧化反应的一些最新进展。由于采用水溶性催化剂，使得水／有机两相体系中的催化反应具有催化剂与产物容易分离的优点。阐述了水溶性催化剂在催化氧化反应中的应用，列举了一些典型的水溶性配体、水溶性催化剂以及催化氧化反应实例。参考文献21篇。     

水溶性均相络合催化研究进展*

本文评述了水溶性膦配体的合成及以水溶性过渡金属膦络合物为催化剂的两相催化体系的研究和开发概况, 着重介绍了两相体系在烯烃氢甲酰化、不饱和化合物的加氢及催化不对称合成中的应用, 并对两相催化体系研究中存在的问题进行了探讨。     

以聚乙二醇为载体的催化剂及为反应介质的催化反应体系

聚乙二醇(PEG)负载的催化剂具有较高的催化活性, 易于回收和循环使用, 因此受到人们极大的关注. 此外, PEG可以用作催化反应的流动相动态地担载催化剂, 通过“均相反应, 两相分离”实现均相催化剂的简单分离. 对这一领域的研究进展作一综述.     

分子氧选择性氧化醇类的研究进展

综述了分子氧化剂的醇类液相催化氧化的新进展。分别介绍了均相催化、水/有机两相催化、氟两相催化和液固多相催化体系。重点讨论了精细有机合成中有广泛应用前景的绿色氧化方法。预测了均相催化剂的多相化是今后工业化发展的趋势。     

金属络合物的相转移催化分析与分离

以可简单分离回收、可反复使用为目标，详细介绍了相转移催化的变化发展过 程．通过对溶剂的选择，使得催化剂选择性地溶解在某一液相中，而使产物溶解在 另一液相中，如水-有机两相催化体系；通过温度的变化，简单地实现了在较高温 度下反应为均相体系以提高催化剂的活性，而在较低温度下实现了催化剂与产物不 相溶使得催化剂得以简单分离，如温控型水-有机两相催化体系、氟-有机两相催化 体系、温控型含氟催化剂、温控型有机金属催化剂等．     

Using Soluble Polymers to Enforce Catalyst‐Phase‐Selective Solubility and as Antileaching Agents to Facilitate Homogeneous Catalysis

The enforced phase‐selective solubility of polyisobutylene (PIB)‐bound Rh^II catalysts in biphasic heptane/acetonitrile mixtures can be used not only to recycle these catalysts but also to minimize bimolecular reactions with ethyl diazoacetate. When cyclopropanation and O? H insertion reactions are carried out with PIB‐bound Rh^II catalysts either with or without addition of an unfunctionalized hydrocarbon polymer cosolvent, dimer by‐product formation is suppressed even without slow syringe pump addition of the ethyl diazoacetate. This suppression of by‐product formation is shown to be due to increased phase segregation of the soluble polymer‐bound catalyst and the ethyl diazoacetate reactant. These studies also reveal that added hydrocarbon polymer cosolvents can function as antileaching agents, decreasing the already small amount of a soluble polymer‐bound species that leaches into a polar phase in a biphasic mixture during a liquid/liquid separation step.     

The use of imidazolium ionic liquids for the formation and stabilization of ir0 and rh0 nanoparticles: efficient catalysts for the hydrogenation of arenes

Stable transition-metal nanoparticles of the type [M(0)](n) are easily accessible through the reduction of Ir(I) or Rh(III) compounds dissolved in "dry" 1-n-butyl-3-methylimidazolium hexafluorophosphate ionic liquid by molecular hydrogen. The formation of these [M(0)](n) nanoparticles is straightforward; they are prepared in dry ionic liquid whereas the presence of the water causes the partial decomposition of ionic liquid with the formation of phosphates, HF and transition-metal fluorides. Transmission electron microscopy (TEM) observations and X-ray diffraction analysis (XRD) show the formation of [Ir(0)](n) and [Rh(0)](n) nanoparticles with 2.0-2.5 nm in diameter. The isolated [M(0)](n) nanoparticles can be redispersed in the ionic liquid, in acetone or used in solventless conditions for the liquid-liquid biphasic, homogeneous or heterogeneous hydrogenation of arenes under mild reaction conditions (75 degrees C and 4 atm). The recovered iridium nanoparticles can be reused several times without any significant loss in catalytic activity. Unprecedented total turnover numbers (TTO) of 3509 in 32 h, for arene hydrogenation by nanoparticles catalysts, have been achieved in the reduction of benzene by the [Ir(0)](n) in solventless conditions. Contrarily, the recovered Rh(0) nanoparticles show significant agglomeration into large particles with a loss of catalytic activity. The hydrogenation of arenes containing functional groups, such as anisole, by the [Ir(0)](n) nanoparticles occurs with concomitant hydrogenolysis of the C-O bond, suggesting that these nanoparticles behave as "heterogeneous catalysts" rather than "homogeneous catalysts".     

Water‐ and Organo‐Dispersible Gold Nanoparticles Supported by Using Ammonium Salts of Hyperbranched Polystyrene: Preparation and Catalysis

Gold nanoparticles (1 nm in size) stabilized by ammonium salts of hyperbranched polystyrene are prepared. Selection of the R groups provides access to both water‐ and organo‐dispersible gold nanoparticles. The resulting gold nanoparticles are subjected to studies on catalysis in solution, which include reduction of 4‐nitrophenol with sodium borohydride, aerobic oxidation of alcohols, and homocoupling of phenylboronic acid. In the reduction of 4‐nitrophenol, the catalytic activity is clearly dependent on the size of the gold nanoparticles. For the aerobic oxidation of alcohols, two types of biphasic oxidation are achieved: one is the catalyst dispersing in the aqueous phase, whereas the other is in the organic phase. The catalysts are reusable more than four times without loss of the catalytic activity. Selective synthesis of biphenyl is achieved by the homocoupling of phenylboronic acid catalyzed by organo‐dispersible gold nanoparticles.     

Heck reactions with various types of palladium complex catalysts: application of multiphase catalysis and supercritical carbon dioxide

The application of multiphase catalytic systems for palladium catalyzed Heck reactions brings several benefits such as easy catalyst-product separation and catalyst recycling. The effective multiphase Heck systems can be prepared by using different types of catalyst phases, including biphasic catalysis and supported liquid phase catalysts, and a new generation solvent of supercritical carbon dioxide.     

Biphasic oligomerization of ethylene with nickel complexes immobilized in organochloroaluminate ionic liquids

Ethylene was selectively oligomerized by nickel complexes such as (PPh₃)₂NiBr₂ and (PPh₃)₂NiCl₂ immobilized in chloroaluminate ionic liquid in biphasic catalytic reactions. The influence of reaction parameters such as reaction media, reaction temperature and Et₂AlCl:Ni molar ratio was also evaluated. Turnover frequency up to 24000 mol C₂H₄/(mol Ni h) was achieved under mild reaction conditions (0.5 atm and 40 °C). GC‐MS analyses showed that the obtained oligomers completely consist of C4 and C6. The olefinic products can be easily separated from the catalytic ionic liquid phase by simple decantation, and the nickel catalyst can be reused without a significant decrease in turnover frequency and change of the distribution of the olefinic products. Copyright © 2009 John Wiley & Sons, Ltd.     

Recycle and recovery of rhodium complexes with water-soluble and amphiphilic phosphines in ionic liquids for hydroformylation of 1-hexene

A biphasic catalysis system composed of ionic liquid and rhodium complexes with water-soluble or amphiphilic phosphine ligands bearing water-soluble groups of sodium sulfonate have been employed for hydroformylation of 1-hexene. The experimental results show that the activity is almost independent of the hydrotropicity of the phosphine ligands in BMI·BF₄. In this system, the extraction of phosphine species by the organics from the IL phase was quite low but larger than that of rhodium species and showed rather good stability of catalytic activity. A slight decrease in the aldehyde n/i ratio during the catalyst reuse could be recovered, in part, by replenishing certain amount of ligand into the used catalyst system.     

Suzuki Coupling Reactions in Neat Water as the Solvent: Where in the Biphasic Reaction Mixture Do the Catalytic Reaction Steps Occur?

Many reports on water‐compatible palladium catalysts have appeared in the recent literature. For hydrophobic substrates, mixtures with pure water are biphasic, and it is widely not regarded that the elusive locality of the catalytic process (in water, the organic layer, or at the phase boundary) has an important impact on the mechanism and efficiency of the reaction. In the present work, for the first time systematic variation of reaction parameters has been performed for Suzuki coupling experiments with chloro‐ and bromoarenes in pure water. The investigations are not only aimed at the factors influencing the catalytic activity, but also at the effects that may occur particularly in water/organic biphasic media, and on the question as to in which of the two liquid phases the reaction takes place. These investigations have revealed that dilution of the base (in the aqueous layer) and the Pd species (in the organic layer) are detrimental to the reaction, and that phase‐transfer processes play a major role in the overall mechanism. A series of experiments with variation of parameters like precatalyst hydrophilicity, organic and water phase volume, additives, stirring rate, base concentration, and so forth, indicate that for the systems under study the reaction occurs in the organic layer. The water phase needs to be present to dissolve and provide polar reactants, and re‐absorb side products. The results encourage to pay more regard to the question of phase locality of coupling reactions in water in general.