Bis(N-Heterocyclic Carbene) Manganese(I) Complexes: Efficient and Simple Hydrogenation Catalysts

The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)-BEt₃ adducts. By applying complexes 3 with KHBEt₃ as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt₃ as cocatalyst.     

L-Shaped Heterobidentate Imidazo[1,5-a]pyridin-3-ylidene (N,C)-Ligands for Oxidant-Free AuI/AuIII Catalysis

In the last decade, major advances have been made in homogeneous gold catalysis. However, Au^I/Au^III catalytic cycle remains much less explored due to the reluctance of Au^I to undergo oxidative addition and the stability of the Au^III intermediate. Herein, we report activation of aryl halides at gold(I) enabled by NHC (NHC=N-heterocyclic carbene) ligands through the development of a new class of L-shaped heterobidentate ImPy (ImPy=imidazo[1,5-a]pyridin-3-ylidene) N,C ligands that feature hemilabile character of the amino group in combination with strong σ-donation of the carbene center in a rigid conformation, imposed by the ligand architecture. Detailed characterization and control studies reveal key ligand features for Au^I/Au^III redox cycle, wherein the hemilabile nitrogen is placed at the coordinating position of a rigid framework. Given the tremendous significance of homogeneous gold catalysis, we anticipate that this ligand platform will find widespread application.     

廉价金属铁、钴、锰配合物催化的加氢/脱氢反应研究进展

催化加氢和脱氢反应是现代化学工业的发展核心.从毫克级有机化学反应探索到吨级化学品的生产,均存在催化加氢和脱氢反应的广泛应用.长期以来,贵金属催化剂是实现含氮及含氧化合物催化加氢和脱氢反应的关键所在.从绿色环保及可持续发展的角度出发,近年来廉价金属催化的加氢和脱氢反应取得了重要的研究进展,本文主要介绍在非贵金属催化的加氢...     

Generation and Stabilization of a Dinickel Catalyst in a Metal-Organic Framework for Selective Hydrogenation Reactions

Although many monometallic active sites have been installed in metal–organic frameworks (MOFs) for catalytic reactions, there are no effective strategies to generate bimetallic catalysts in MOFs. Here we report the synthesis of a robust, efficient, and reusable MOF catalyst, MOF-NiH, by adaptively generating and stabilizing dinickel active sites using the bipyridine groups in MOF-253 with the formula of Al(OH)(2,2′-bipyridine-5,5′-dicarboxylate) for Z-selective semihydrogenation of alkynes and selective hydrogenation of C=C bonds in α,β-unsaturated aldehydes and ketones. Spectroscopic studies established the dinickel complex (bpy⋅⁻)Ni^II(μ₂-H)₂Ni^II(bpy⋅⁻) as the active catalyst. MOF-NiH efficiently catalyzed selective hydrogenation reactions with turnover numbers of up to 192 and could be used in five cycles of hydrogenation reactions without catalyst leaching or significant decrease of catalytic activities. The present work uncovers a synthetic strategy toward solution-inaccessible Earth-abundant bimetallic MOF catalysts for sustainable catalysis.     

高活性的茂基钛配合物／正丁基锂加氢催化体系的研究

考察了茂环上不同取代基及钛上阴离子配体对茂基钛配合物／正丁基锂催化体系加氢活性和稳定性的影响。在充分发挥该体系催化活性的条件下，由配合物Ｃｐ２ＴｉＣｌ２、Ｃｐ２ＴｉＦ２和Ｃｐ２Ｔｉ［ＯＣ６Ｈ３（ＣＨ３－２）Ｃｌ－４］２组成的催化体系对辛烯－１加氢的最高活性（或初活性）达到４６￣５８ｓ＾－１。     

YDHC-10催化剂用于不饱和植物油脂肪酸氢化工艺条件的研究

采用自制的催化剂YDHC-10对氢化工艺条件进行了研究。找出了植物油脂肪酸氢化时,氢化压力2MPa、氢化温度180-200℃、氢化时间60min以及催化剂浓度对植物油脂肪酸氢化的影响．     

Versatile Iridicycle Catalysts for Highly Efficient and Chemoselective Transfer Hydrogenation of Carbonyl Compounds in Water

Cyclometalated iridium complexes are shown to be highly efficient and chemoselective catalysts for the transfer hydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α‐substituted ketones (α‐ether, α‐halo, α‐hydroxy, α‐amino, α‐nitrile or α‐ester), α‐keto esters, β‐keto esters and α,β‐unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of up to 50 000 at pH 4.5 and required no organic solvent. The protocol provides a practical, easy and efficient way for the synthesis of β‐functionalised secondary alcohols, such as β‐hydroxyethers, β‐hydroxyamines and β‐hydroxyhalo compounds, which are valuable intermediates in pharmaceutical, fine chemical, perfume and agrochemical synthesis.     

A Highly Active Manganese Catalyst for Enantioselective Ketone and Ester Hydrogenation

A new hydrogenation catalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives up to 97 % ee in the hydrogenation of pro-chiral deactivated ketones at 30–50 °C.     

水溶性含钌-铂双金属催化剂催化卤代芳香硝基化合物选择性加氢

考察了水溶性Ru/Pt-TPPTS双金属催化剂催化卤代芳香硝基化合物的加氢性能.实验结果表明,在Ru-TPPTS中添加铂或钯后,反应活性明显提高,尤其是Ru/Pt-TPPTS双金属催化剂更表现出显著的双金属协同效应.在pH₂=1.0MPa,70℃,反应2h的条件下,双金属催化剂0.50Ru/0.50Pt-TPPTS催化对-氯硝基苯加氢生成对-氯苯胺的反应转化率达到100%.对于取代基和取代位置不同的一些卤代硝基苯加氢,该双金属催化剂也表现出很高的催化活性和生成卤代苯胺的选择性,脱卤反应的程度很小.     

Synthesis and Characterization of High Surface Area Tin Oxide Nanoparticles via the Sol‐Gel Method as a Catalyst for the Hydrogenation of Styrene

A systematic study on the preparation of SnO₂ nanoparticles using a simple sol‐gel technique has been conducted by varying reaction parameters such as concentration of ammonia, ammonia feed rate and reaction temperature. The tin oxide obtained was characterized by using FTIR, BET, XRD and TEM. Particles size was obtained in the range of 4 to 5.6 nm and the surface area was found to be between 76 to 114 m² g^?1 depending on the reaction parameters. Meanwhile, the catalytic activity of SnO2 was first time investigated for the hydrogenation reaction of styrene using ethanol as the solvent at 70 °C and 1 atmospheric pressure. It is found that SnO2 acts as a good catalyst in this hydrogenation process. The product conversions in the presence of catalysts prepared at different conditions were between 37 to 72%.     

A State-of-the-Art Heterogeneous Catalyst for Efficient and General Nitrile Hydrogenation

Cobalt-doped hybrid materials consisting of metal oxides and carbon derived from chitin were prepared, characterized and tested for industrially relevant nitrile hydrogenations. The optimal catalyst supported onto MgO showed, after pyrolysis at 700 °C, magnesium oxide nanocubes decorated with carbon-enveloped Co nanoparticles. This special structure allows for the selective hydrogenation of diverse and demanding nitriles to the corresponding primary amines under mild conditions (e.g. 70 °C, 20 bar H₂). The advantage of this novel catalytic material is showcased for industrially important substrates, including adipodinitrile, picolinonitrile, and fatty acid nitriles. Notably, the developed system outperformed all other tested commercial catalysts, for example, Raney Nickel and even noble-metal-based systems in these transformations.     

Ni—S油脂氢化催化剂的EXAFS研究

用EXAFS法测定了Ni-S油脂氢化催化剂的结构。Ni催化剂被硫中毒生成了Ni_3S_2,致使由3个Ni原子组成的空穴(3CN)数目减少,这样虽引起该催化剂的活性降低,但却提高了油脂氢化对生成反式油酸酯的选择性。     

Y型分子筛超笼内酞菁锰的合成及对烯烃形状选择性催化环氧化反应研究

酞菁锰(MnPc)具有与四苯基卟啉锰(Mn TPP)相似的大环结构,因此金属酞菁用于烯烃催化环氧化的研究,被认为是对细胞色素P-450体系的模拟。催化剂的活性中心是MnPc与单氧源作用生成单氧锰络合物O=MnPc(O×O络合物),在反应中它除了能催化烯烃环氧化外,还会氧化催化剂本身,或发生二聚作用,使催化剂失活。生物酶具有高的选择性和催化活性,除了与酶活性中心有关外,还与酶中蛋白质的三级结构有关,因此活性中心周围的空间结构对反应的选择性和催化活性是非常重要的。人们用具有特殊结构及性能的Y型分子筛,试图来代替细胞色素P-450酶的蛋白质,希望获得特殊的选择性和高的催化活性。有     

A new class of readily available and conformationally rigid phosphino-oxazoline ligands for asymmetric catalysis

A new class of conformationally rigid phosphino-oxazoline ligands 3 were synthesized via an efficient ortho-substitution of phenyl glycinol as the key step. Divergent synthetic routes for easy ligand modulation, as well as a procedure suitable for scale-up synthesis, were established. The catalytic potential of ligands 3 has been demonstrated in the highly enantioselective Ir-catalyzed hydrogenation of alkenes and Pd-catalyzed allylic substitution and intermolecular Heck reactions.     

氧化锆负载氧化铁催化剂上CO加氢反应的研究钾,锰,镧,铈的助剂作用

应用Ｘ－射线衍射，程序升温还遥，穆斯堡尔谱以及ＣＯ＋Ｈ２催化反应性能测试等手术研究了Ｋ，Ｍｎ，Ｌａ，Ｃｅ四种助剂对Ｆｅ２Ｏ３／ＺｒＯ２催化剂结构，还原行为以及ＣＬ＋Ｈ２反应催化性能的影响。     

含氮聚合物负载钯络合物的合成及其催化加氢性能的研究

合成了一系列含氮聚合物金属络合物,考察了它们对1,5,9-环十二碳三烯选择性催化加氢的活性及选择性。研究了同种聚合物中单原子配体与双原子配体对催化剂活性的影响。对不同金属物种、孔结构、温度及压力对加氢活性及选择性的影响也进行了系统的比较。     

Development of a General and Selective Nanostructured Cobalt Catalyst for the Hydrogenation of Benzofurans,Indoles and Benzothiophenes

The selective hydrogenation of benzofurans in the presence of a heterogeneous non-noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt-cobalt oxide core–shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt-DABCO-citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3-dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co-nanocatalyst are demonstrated.     

A High-Valent Ru-PCP Pincer Catalyst for Hydrogenation of Carbonyl and Carboxyl Compounds under Molecular Hydrogen

Low-valent metals traditionally dominate the domain of catalytic hydrogenation. However, metal-ligand cooperating (MLC) catalytic systems, operating through heterolytic H−H bond splitting by a Lewis acidic metal and a basic ligand site, do not require an electron-rich metal. On the contrary, high-valent metals that induce weaker back donation facilitate heterolytic bond activation. Here we report, for the first time, the efficient hydrogenation of carbonyl and carboxyl compounds under molecular hydrogen catalyzed by a structurally well-defined Ru^IV catalyst bearing a bifunctional PCP pincer ligand. The catalyst exhibits reactivity toward molecular hydrogen superior to that of the low-valent analog and allows hydrogen activation even at room temperature.     

A Simple and Efficient Palladium Catalyst of Nitrogen-Based Ligand for Cu(I)- and Amine-Free Sonogashira Reaction

Glycine, as a kind of commercially available and inexpensive ligand, is used to prepare an air-stable and water-soluble catalyst used in Sonogashira reaction in our study. In the presence of 1% [PdCl₂(NH₂CH₂COOH)₂] as catalyst, excellent catalytic activity towards the Sonogashira coupling of aryl iodides with terminal alkynes without using any additive such as Cu(I)-cocatalyst is observed in a mixture of water and acetone (3/3 mL) under air at 60 °C with NaOH as a base, giving products in good to excellent yields.